Maine Organic Farmers and Gardeners Association
MOFGA’s 2012 Spring Growth Conference: The Tomato

Publications \ The Maine Organic Farmer & Gardener \ Fall 2012 \ Tomato

2012 Spring Growth Conference logo

Participants in MOFGA’s 2012 Spring Growth Conference learned about field- and hoophouse-grown tomatoes, including some nitty-gritty details from growers that help ensure success with the crop.


Basic Botany

Mark Hutton, the University of Maine Cooperative Extension vegetable specialist stationed at Highmoor Farm in Monmouth, told participants that tomatoes are native to South America, were brought to Europe in the 1400s and used as ornamentals there. Commercial production of the fruits for eating began around 1860. Breeding for improved quality and production began around 1890.

Perennial in its native area, in the North the tomato is grown as an annual outdoors or for nine to 12 months in a greenhouse. It’s a warm season crop with an optimum temperature of 60 to 90 F. Temperatures below 55 result in poor growth, poor fruit set and a lack of fruit quality. Above 90 F, fruit set is poor and quality is lacking – so keep hoophouses vented to avoid such heat, said Hutton.

Two types of tomatoes exist: determinate and indeterminate. Determinate grow to a genetically predetermined size, have flower clusters generally separated by one or two nodes and tend to concentrate fruit set in time. They are grown on the ground or, for improved yield and quality, are staked.

Indeterminate varieties are vining and require pruning and support. They produce over a long period and include ‘Brandywine’ and cherry tomatoes. Generally three or more nodes grow between flower clusters. Most people prefer the quality and taste of indeterminate fruits, said Hutton.


Site Selection and Soil Preparation

Tomatoes need a well-drained, non-compacted soil with a pH of 5.5 to 6.8 (with better taste at the higher pH). A survey of high tunnel soils in Maine showed pH levels around 6.1, but some around 5.

Good air movement helps minimize foliar diseases, so orient rows with the prevailing winds, suggested Hutton. Raised beds and plastic mulch increase yields, quality and earliness. Plastic increases soil temperatures by about 5 F on average.

Organic growers should front load all nutrients, said Hutton, then take a tissue test when plants flower. Plants need 80 to 90 pounds per acre of N (more can produce excess vegetative growth at the expense of fruiting), 100 pounds of P2O5 and 100 to 200 pounds of K2O. Getting enough P is generally not an issue because repeated manure applications have built up that nutrient. Potassium “is the big one for tomatoes,” said Hutton. Those 100 to 200 pounds are just what plants take from the field. If fruit quality issues occur, increasing K may help. “You want it to be at the upper end of the range.”


Starting Seedlings and Establishing Plants

Tomato transplants take five to six weeks to produce. At Highmoor Farm, seeds are sown in early to mid-April for transplanting in early June. Seeds are sown in bands in trays filled with a lightweight, well-drained medium. The trays sit on heating mats, stacked atop one another, and the soil temperature is kept around 80 F for the first 24 to 48 hours, until the seeds sprout. Then the trays are spread out on heating mats.

When plants reach the cotyledon stage, they’re transplanted; each seedling is held by the cotyledon and transferred to large trays, with 48 plants per tray. The air temperature is then kept in the 70s and not below 60 or 65. Planting in trays is “essentially doing soil blocks,” said Hutton. They prefer this method at Highmoor, because “then you can grow bigger transplants and hold them if the weather is bad at planting time.” They block the soil (cut it into squares, like pieces of cake) when plants have two to three leaves; cutting prunes roots, which checks top growth and stimulates root growth into a consolidated root ball. They repeat this at the four-leaf stage and again if weather delays planting. Even with a preformed soil block, you may want to root prune, said Hutton, to keep roots from growing into the next soil block.

The greenhouse is kept at a minimum of about 65 F at night. The temperature could be lower with row cover over seedlings. “Having the bottom heat is going to be the most important thing,” said Hutton.

Too much water and not enough light are the two greatest hindrances to growing transplants.

Harden plants off in a coldframe or sheltered location for three or four days before transplanting them to the field, said Hutton, to accustom them to outside temperatures, increased sunlight and wind.

Use quality, actively growing transplants, he continued. Maximize soil warming by using raised beds and applying black plastic mulch a few days before transplanting. Transplanting through black plastic mulch into soil that has reached 60 F at 3 inches of depth can reduce the time to maturity by seven to 14 days compared with not using plastic mulch at all, he said.

Red mulch generally is not cost effective in Maine. Research in Pennsylvania found increased yield from red mulch in three of five years – not enough to be economical. “And you get a lot more weed growth under red plastic than with black plastic,” said Hutton – but red mulch can draw customers who are curious about the color, he added.

If you’re using organic mulch, which keeps soils cool, Hutton said not to apply it until mid-June, after plants are established.

When transplanting, use a starter solution such as fish emulsion in the transplant water, or applied just before transplanting. Give each plant about 1 cup of water after transplanting to eliminate air pockets in the soil. Conventional growers use about 1 tablespoon per gallon of starter solution with a 12-48-48 analysis. “You’re really looking for P in the transplant solution,” said Hutton, “for good root growth.” Plants have difficulty taking up P from cool soils. Organic growers might use a solution of about 1 gallon of an approved liquid fish fertilizer to 25 to 50 gallons of water.

Set 2,600 to 5,800 plants per acre, said Hutton, spaced 18 to 30 inches apart within rows, depending on the variety and whether it will be staked and pruned; and space rows 5 to 6 1/2 feet apart on center – a choice that usually depends on equipment.



Pruning increases earliness and fruit size, produces more uniform fruit and can help reduce diseases by increasing airflow. Indeterminate plants must be pruned so that they will be reproductive instead of just vegetative. Pruning takes time and can spread diseases, especially viruses – so don’t let smokers near tomato plants, because they can spread viruses from tobacco to tomatoes.

Remove leaves and suckers below the lowest flower cluster once the first flower clusters appear – usually in late June or early July. Those leaves “are not adding anything to the plant at that stage, and that’s where diseases generally start,” said Hutton. If you’re growing plants to two leaders, let the first sucker below the lowest flower cluster become the second leader. If this is the only pruning you do for field tomatoes, that’s fine.

Plants are turgid early in the day, so suckers are easiest to snap off with your fingers then; Hutton prefers to cut them off with clippers.



Hutton discouraged using concrete reinforcing wire cages to support tomatoes because they almost always fall over and need to be staked to stay upright – although they’re great for cherry or grape tomatoes, he said. Large fruits are often scraped against the wire when being picked. Cages can harbor some diseases, particularly some bacterial diseases, if they’re not soaked and washed each year.

In a hoophouse, tomatoes are trellised to poles going across rafters. Likewise, in an open field, trellises can be made using posts with 12-guage wire going across.

Basket weaving (which Hutton shows at is the standard way to support plants between posts in open field production; is typical with determinate varieties; and will also work with indeterminate varieties in the open field. Use a 4-foot stake about 1 foot in the ground for determinate tomatoes and a 5-foot stake about 1 foot in the ground for indeterminate. Set one stake between every two or three plants.

Top plants when they’re about the height of the stakes.

To weave twine around plants, get 3-pound balls of twine in a box, put the box on a belt loop, thread the string through a 1-1/2- to 2-foot piece of PVC pipe, tie the string to the first stake, then use the pipe to weave the string from stake to stake, down the row, winding it around each stake a couple of times and pulling it tight at each stake. Tie the twine to the end stake. Then come back up the other side, weaving string on the other side of the plants.

As plants grow, put the first string 10 to 12 inches above the ground; the second 18 to 24 inches above; and the third another 12 inches above the second. Maine growers usually use about four tiers of twine. End stakes need to be braced. Especially with indeterminate varieties, align rows so that wind blows down the rows, not into them, to prevent the wind from blowing the whole structure over.


Physiological Disorders

Hutton covered disorders caused by abiotic environmental conditions, and then Eric Sideman, MOFGA’s organic crop specialist, talked about insect and disease problems.

Blossom end rot indicates a lack of calcium and/or a lack of water, said Hutton. Ninety percent of the calcium needed for fruit development is needed before fruit begin to size. When you see blossom end rot, it’s too late to do anything about it. To avoid the problem, maintain steady plant growth by having even soil moisture, supplying an inch of water per week. If watering is uneven, the plant removes calcium from growing tips, so it’s not available for cell wall formation, and that deficiency shows up as blossom end rot. Soil testing will tell if you have enough calcium for the growing season. Both Hutton and Sideman noted that blossom end rot is more often a water management than a calcium management issue, and that in addition to dry soils, waterlogged soils can lead to blossom end rot as they create nonfunctional roots.

Catfacing can be caused by high or low temperatures during fruit set; by moisture stress; or by herbicide drift. It is prevalent in heirloom varieties, especially those with a fused stigma.

Yellow shoulder occurs when, at temperatures above 85, the pigment lycopene fails to develop and only carotene is present. This is especially problematic with varieties that have the gene for green shoulder.

Gray wall or blotchy ripening occurs under low light or prolonged cloudy conditions; with excess N and plant vigor; with high soil moisture; potassium deficiency; and soil compaction. Hutton sees it a lot in hoophouse production.

Internal white tissue is due to potassium deficiency under high temperatures; some varieties are more susceptible than others. It does not occur often in open field production but does in hoophouses.

Once these problems appear, it is too late to solve them. “Know your soil,” said Hutton. “Pay close attention to K, Mg, Ca, pH and organic matter (ideally 4 to 6 percent).” A uniform color requires more potassium than is necessary for optimum yields, so manage soils to increase available K and/or decrease available magnesium, since these two cations (positively charged ions) compete with each other for uptake into the plant. Have a soil pH of 6.2 to 6.5.

Zippering – tiny scars that extend from the stem end of the tomato to the blossom end – seems to be related to high temperatures and humidity. Growers can’t do much about this.

Sunscald occurs after excess pruning or leaf loss due to diseases (typically early blight and septoria leaf spot). Tissue temperatures above 104 F will kill those tissues; this temperature is possible on exposed fruit on a hot sunny day.

Late blight on tomato leaves
Late blight on tomato leaves. Eric Sideman photo.
Late blight on tomato stems
Late blight on tomato stems. Eric Sideman photo.
Late blight on tomato fruits
Late blight on tomato fruits. Eric Sideman photo.
Late blight spores on a tomato fruit
Late blight spores on a tomato fruit. Eric Sideman photo.

Puffiness – flat sides or angular fruit – occurs after temperatures are too high (e.g., night temperatures above 75) or too low; when N is too high and K is low; or with low light. Some heirlooms and paste tomatoes are more prone to this disorder. It’s often seen in high tunnels late in the season.

Rain check – tiny cracks that heal over on the shoulders of fruits – occurs more often on green fruits and when heavy rains follow dry periods. Good foliage cover and selected varieties can minimize the problem.

Growth cracks are usually related to watering issues, such as sudden excess water.



Late blight (Phytophthera infestans) is a community disease, said Sideman. It shouldn’t occur, because good sanitation and management should take care of it (although a couple of years ago it came to the Northeast on tomato seedlings grown in the South and sold here in big box stores). It shows up as dark brown to black lesions with no yellowing around them (as in early blight and Septoria leaf spot). Lesions occur on leaves, stems and fruits.

Late blight begins early in the growing season on infected potato tubers. It’s an obligate parasite, overwintering only in living tissue. While top growth usually freezes and dies over winter, tubers may survive and enable the disease to survive as well. When infected tubers sprout, those sprouts produce sporangia with spores that, under the right weather conditions, blow in the air. Spores survive for only about eight hours in the sun but during cloudy, damp weather can blow for miles. If they land on a potato or tomato plant, they can germinate.

“So don’t plant infected tubers,” said Sideman.

Likewise, don’t pile or compost cull potatoes, because the middle of the pile may not freeze or, in a compost pile, may not get hot enough to kill the disease. Potatoes spread evenly on the ground will freeze, but those buried 6 to 10 inches deep will not.

And don’t save questionable seed potato; instead, buy new seed from a good source.

During the growing season, scout and remove volunteer potatoes. If late blight occurs on tomatoes during the growing season, bury dying plants or pile them and cover them with a tarp to reduce the number of spores in the environment so that neighbors’ plantings are protected. By the end of the season, don’t worry about blight-infected tomato plants, said Sideman. Just let them die and freeze.

Maine has only one or the other of the two mating types of late blight – A1 or A2 – so the disease does not reproduce sexually here, and no oospores exist to overwinter.

Once late blight is in Maine, only copper (e.g., Champ WG) gives consistent protection. Sideman told growers to “use an approved material [for organic production] and in a manner that does not lead to accumulation in the soil. You need to soil test.”

Late blight won’t overwinter on tomato cages (although other diseases, including Septoria and early blight, will) or on tomato seeds. But in a greenhouse that’s kept warm all winter – growing greens, for example – tomato seed can germinate and become infected from residue of earlier-grown tomato plants.


Fusarium and Verticillium wilt are soilborne diseases that survive in soils for several years. Plants are generally affected through their roots. Two- to three-year rotations offer control, as do resistant varieties. Most tomato varieties are resistant, although some heirlooms may be susceptible.

Strawberries, potatoes and tomatoes can all get Verticillium, so don’t rotate solanaceous crops with one another or with strawberries.


Septoria on tomato leaves
Septoria on tomato leaves. Eric Sideman photo.

Septoria leaf spot is common on tomatoes in Maine. The disease appears as small spots all over the leaves (and possibly on stems), with gray areas inside the spots where spores are produced. The disease overwinters on tomato debris – even dead tissues; on other Solanaceous crops; and on debris on tools, stakes, used plastic mulch, etc. It can be seedborne, but seed produced in arid areas is clean, said Sideman.

Once introduced, spores spread by splashing water and movement of workers and windborne soil.

Controls include rotating crops every year or two; using clean seed; reducing leaf wetness; mulching to prevent initial spores from splashing out of the ground; controlling solanaceous weeds; using copper fungicides; pruning off lower leaves before they start releasing spores (this also improves air circulation around the plants, enabling plants to dry faster); and cleaning stakes and cages with Oxidate or a chlorine solution approved for organic growing.


Anthracnose, according to Cornell University (, will “appear on ripe fruit as small, slightly sunken, water-soaked circular spots. The lesions increase in size, become more depressed, and the central portion darkens. The darkened area contains many small, dark, fungal structures from which masses of salmon-colored spores are released in moist weather. As the fungus spreads within the fruit, a semi-soft decay occurs. Anthracnose lesions on a single fruit often merge and result in large rotted areas. In addition, secondary organisms often move into these lesions and rot the fruit completely.

“The fungus can infect both green and red fruit and is able to penetrate the cuticle of uninjured fruit. When green fruit is infected, it does not show spotting until it begins to ripen. Tomato fruit become increasingly susceptible as they approach maturity. On ripe fruit, lesions become visible within 5 to 6 days after infection.”

The disease can develop after harvest and affect fruit flavor, said Sideman.

He said the microsclerotia (resting bodies of the fungus) that cause anthracnose overwinter on seed and plant debris and, once they start growing, can produce hyphae and spores. This is one reason staking is recommended: Tomatoes sitting on the ground can come in direct contact with hyphae growing from the previous year’s infections, or the microsclerotia can germinate and produce spores that blow in the wind.

Control includes using disease-free seed; a three-year rotation; trellising plants; managing water; and controlling weeds.

“This is why high tunnels became popular – to get away from these diseases,” said Sideman. “But they only change which diseases we have. Leaves no longer are drenched in rain, but it’s always humid in a house, especially if it’s mismanaged.”


Early blight on tomatoes
Early blight on tomatoes. Eric Sideman photo.

Early blight is the other common problem on tomatoes in Maine. It appears as concentric ring lesions, like oyster shells. It can also affect fruits, usually at the stem end. It overwinters in crop debris. The initial infection is by splashing spores from the soil, but “by midsummer, the air is filled with early blight spores,” said Sideman.

Controls include rotating crops over two to three years; using clean seed and resistant varieties; reducing periods of leaf wetness; using a clean soil mix; and applying copper fungicides. Copper kills spores as they germinate, so the material needs to be on the leaf before spores germinate. Copper won’t be able to save a leaf that already has early blight symptoms, so a fungicide must be applied every five, seven, 10 days – depending on the weather – to save foliage that hasn’t been infected already. Rain will wash copper off plants, requiring more frequent spraying.

Removing leaves that show symptoms can help but is not a panacea, since early blight symptoms take up to 10 days after inoculation to appear.

PlantShield, a strain of Trichoderma fungus, applied in a potting mix or drenched in the soil, helped control early blight in replicated trials, said Sideman.

Early blight takes advantage of any stress on the plant, Sideman continued, including water stress, potassium deficiency, cloudy weather, too much shade and dry weather.


Gray mold on tomato Botrytis on tomato leaf
Gray mold (Botrytis) on tomato. Gray mold on a tomato leaf. Eric Sideman photos.

Gray mold (Botrytis) is probably worst in high tunnels, where high humidity and cool temperatures encourage spores to germinate. When gray mold spores land, they need energy to start growing. They get that energy from rotting tissue, so the disease appears on dying leaves and blossoms. When sepals fall off and land on a leaf, the disease spreads.

Controls include reducing humidity with heat and ventilation; keeping the calcium to phosphorus ratio at 2:1 or higher in a leaf petiole test; and keeping plastic clear, as dim plastic reduces light transmission.

Blossom end rot can be a problem in itself, and can enable Botrytis to come in as a secondary problem. Remove affected fruit to limit the spread of Botrytis, said Sideman.


Leaf mold on top of tomato leaf Leaf mold on the bottom of a tomato leaf
Leaf mold on the top of a tomato leaf.
Leaf mold on the bottom of a tomato leaf. Eric Sideman photo.

Leaf mold (Fulvia fulva), the second most common problem in high tunnels, is favored by high humidity and warm temperatures. It shows up as yellowing on top of the leaf and, on the underside of the leaf, as a little speck of gray fuzz under each spot.

Sideman offered one control: “Go for the early market. Try to get rid of all your fruit in July and empty the house in August. Then you get rid of leaf mold.”

Leaf mold doesn’t affect fruit but eventually lowers yields. Controls include sanitation (the disease overwinters as spores on equipment, in the planting shed, in soil …) – including steam cleaning the house between growing seasons; and – the key – minimizing periods of leaf wetness. Open the house to ventilate it, said Sideman. Susceptible varieties include ‘Jet Star’, ‘Big Beef’ and ‘Ultra Sweet’; resistant include ‘Better Boy’ and ‘Lemon Boy’.


White mold sclerotia on a tomato stem Effects of white mold on a tomato vine
White mold sclerotia on a tomato stem. Effects of white mold on a tomato plant. Eric Sideman photos.
White mold (Sclerotinia sclerotionum) has an enormous host range (peppers, carrots, beans…); can live in soil for up to 10 years; and can survive composting – so pull affected plants and bring them to the dump, said Sideman. A single plant or half a plant in the whole house may go down.

Dried sclerotia (dark bodies that are dried up pieces of the fungal body) are visible inside stems if you cut them open. Some sclerotia can live for several years. They have to land on dying tissue to germinate.


Mustard as Soil Fumigant

During the discussion, Barbara Damrosch said that at Four Season Farm, mustard meal was tilled into the soil three to four weeks before tomatoes were transplanted in greenhouses. The soil was then covered with clear plastic. Treatment with mustard meal was as effective as grafting for disease control.

Hutton said he grew ‘Caliente’ mustard in April or May in a hoophouse. Just before it flowered, he flail mowed it, tilled it in and watered the soil. He got an increase in yield and plant health, but also saw more Sclerotinia because mustards host that disease.

Tomato hornworms
Tomato hornworms. Photo by Eric Sideman.
Tomato hornworm with Braconid wasp cocoons
Tomato hornworm with Braconid wasp cocoons. Photo by Eric Sideman.

Similarly, said Hutton, when mustard or mustard meal was rotated with potatoes in Aroostook County, some diseases were suppressed, others increased.

“Basically you’re putting hydrogen cyanide in the soil,” said Hutton, “so you’re killing the good things and the bad things.”


Hornworms, said Sideman, are revealed by their dark frass on or under plants. They are very susceptible to Bt. Other speakers recommended closing hoophouses at dusk to keep the adults from flying in; hornworm and tomato fruitworm adults fly at dusk and at night. Hoophouses must be opened or ventilated by 5:30 or 6 a.m.


Spotted wing drosophila can attack sound fruit. Entrust can control it, but with 13 generations per year, growers would have to spray every three to five days. “We’re not sure if it will be a problem on tomatoes or not,” said Sideman

In greenhouse tomatoes, some growers leave a couple of sacrificial cracked fruit away from the high tunnel, luring flies away from sound fruit in the tunnel. You can trap these flies with cider vinegar to determine how many are present, but they are too numerous to trap all of them.

Regarding a suggestion to exclude the flies by covering the house with ProtekNet, Hutton said, “Now your high tunnel is becoming a greenhouse” that requires more management for airflow, ventilation and other care.

Regalia, a biological fungus derived from knotweed, is doing well in trials by Meg McGrath at the Long Island Horticultural Research & Extension Center.


Pollination in High Tunnels

Pruning will usually shake plants enough to pollinate the flowers. Growers can bring in bumblebees if tunnel sides are down and if wind or vibration is insufficient to pollinate the plants. Nate Drummond, one of the farmers who spoke at Spring Growth, brings in bumblebees on the advice of his father, UMaine entomologist Frank Drummond.



Hutton said to harvest tomatoes by gently twisting fruit off the plant (rough handling may cause damage that won’t show up until later) and putting it in clean containers – no more than one or two layers high in a flat box; or filling bushel containers just to the top. To avoid sunburn, don’t let harvested fruit sit in the sun too long.



Hutton said some growers love grafting tomatoes, others hate it. It is very expensive, but pays off if the variety you want to grow does not have a vigorous root system or if you’ve got soilborne diseases – which is possible if tomatoes grow in the same house for years.


Row Covers

When covering tomatoes or peppers with row covers, support the covers with hoops, since these plants don’t tolerate abrasion. Remove the covers one or two weeks after transplanting to avoid excess heat, which can kill flowers.

By July, the sides of the hoophouses at Highmoor are rolled up most of the time.


UNH Variety Trials

University of New Hampshire graduate student Nick Warren discussed the first year (2011) of variety trials he’d done with tomatoes in a high tunnel in Durham, N.H. He grew 11 varieties of ungrafted indeterminate beefsteak tomatoes and three varieties of orange cherry tomatoes in a 30- by 60-foot tunnel from April until November. Plants grew in raised beds with black plastic mulch and drip tape. Six rows were planted, 4-1/2 feet on center, with 16 inches between plants within rows. Plants were pruned to a single leader and were trellised, and lower leaves were removed.

Warren applied 100 pounds of soymeal before planting and did not see any nutrient deficiencies during the growing season.

Seeds were germinated on April 19 in a heated greenhouse and moved to the tunnel on May 20. The first flowers appeared on June 2 and the first fruit was harvested on July 12.

Watering occurred often twice per week (three times during unusually hot weather) for two to four hours each time.

The only pesticide used was Bt.

Warren saw a little damping off, cutworm damage and hornworm damage after transplanting. A serious problem occurred when the trellis string broke around midseason. He and a few other students spent about a week replacing it with blue and white twine from Nolt’s Produce Supplies in Leola, Pennsylvania (

The yellow striped armyworm was the worst pest, first on leaves and then on some fruit. A single Bt spray controlled the armyworm and hornworm.

Warren saw spotted wing drosophila but saw no evidence of its damage.

Disorders included splitting, rain checking, a little anthracnose, uneven ripening (including graywall and blotchy ripening), yellow shoulder and catfacing.

At harvest Warren divided fruit into three categories: best (little or no physiological disorders or diseases on fruit); seconds (fruits with just enough cracking or yellow shoulder that they may not sell); and culls (split fruit, with exposed flesh and possibly some mold). Results follow:


Marketable Yield

Cultivar (a)
Fruit Size
Yield (b)
Percent Unmarketable (c)
Taste (d)
Days to Maturity (e)



Arbason (JSS)
Big Beef (HS)
Brandywine (HS)
Cobra (JSS)
Conestoga (HS)
Geronimo (JSS)
Imperial 643 (RP)
Jet Star (HS)
Lola (HM)
Masada (JSS)



Goldie (SW)

na 10.6 13.6 4.1 55 55
Sun Gold (JSS) na 8.1 24.4 4.0 53 53
Toronjino (HM) na 7.1 28.7 3.8 53 53

a Cultivars purchased from Johnny’s Selected Seeds (JSS), Harris Seed (HS), Seedway (SW), Rupp (RP) and High Mowing (HM).
b Marketable yield as average pounds per plant over entire season
c Percentage of fruit that was not salable
d Average scores for two taste tests conducted in August and October; ratings: 5 = best; 1 = worst
e Days after transplant until first fruit/Days until consistent fruit production

Uneven ripening was the most frequent problem, followed by radial cracking, yellow shoulder, splitting, rain checking, concentric cracking and catfacing. In ‘Brandywine’, splitting was the most common problem leading to cracking, but yellow shoulder was also common (which is a trait of this heirloom and is not necessarily a reason for culling). For ‘Masada’, concentric cracking was the most common problem; for ‘Lola’, radial cracking.

The greatest marketable yield occurred between late August and early September, although different varieties peaked at different times. Around mid-August, ‘Big Beef’, ‘Jet Star’, ‘Arbason’, ‘Conestoga’ and ‘Brandywine’ peaked, while ‘Geronimo’, ‘Imperial’, ‘Masada’ and ‘Cobra’ peaked in early September. ‘Lola’ and ‘Trust’ had no distinct production peak, and Warren didn’t notice any correlation between time of peak production and total yield.

Two taste tests – one in August at a field day and one in October with student volunteers – had varying results. ‘Conestoga’ did well in August but poorly in October. ‘Lola’ did poorly in August but was one of the best in October. Many students said ‘Brandywine’ was juicy, sweet and soft.


Growers’ Experiences

Dave Colson, MOFGA’s agricultural services director, has been growing tomatoes at his New Leaf Farm in high tunnels with heat (so, technically, in greenhouses) and in fields.

New Leaf Farm originally grew tomatoes in the field – and lost about 50 percent to diseases.

Then tomatoes were planted through black plastic and grown under tunnels made with 10-foot-long, 1/2- or 3/4-inch PVC pipe set 1 foot in the ground on each side. The hoops were covered with 20-foot-wide by 100-foot-long UV-resistant 1-year greenhouse film sliced down the centerfold to make two 10-foot pieces. The 4 mil film lasted for four years. (Construction-grade plastic breaks down quickly under UV light, said Colson.) These tunnels, about 3 feet high, covered lettuce in early spring, tomatoes and peppers in midspring, and spinach in winter.

The plastic was on tomatoes for about a month, being propped up on the sides with boards for about two weeks; and being removed during the day and replaced at night for two more weeks. Then it was removed, rolled up and stored for summer. The hoops were left in place so that the plastic could be reapplied over peppers and tomatoes in the fall.

Then Colson made a 12- by 48-foot PVC hoophouse using 1-1/4-inch, 20-foot-long PVC pipe raised on a hip wall. This was not a winter structure. Each year it was moved to new ground.

“We grew gorgeous tomatoes in there,” said Colson.

He made a similar 96-foot-long house, which a windstorm took away and the tomato crop was lost.

Next New Leaf bought Griffin’s Inflation Buster houses, which are 17 by 96 feet long and have roll-up sides. Colson added heaters to these. He planted three beds – two outside beds with double rows of tomatoes, and a middle bed with peppers or basil – high income crops that are low-growing and so improve air flow. Peppers are supported with a basket-weave system with rebar stakes at the ends of rows. He begins heating the house around mid-March for an initial June harvest.

Colson likes the 500-foot-long soaker hose he got from A. M. Leonard better than drip tape because it lasts so long – some for 12 years so far. Soaker hose from hardware stores doesn’t last so long, said Colson.

Most recently New Leaf bought a 30- by 96-foot gambrel-shaped Ledgewood house with exhaust fans and a thermostat. This shape makes pruning and tying plants on edges easier. Eric Sideman noted that fans have to be sized to a house; he has information on sizes.

Colson closed the house at night to exclude flying insects – and that led to an increase in leaf mold. He realized that ‘Lemon Boy’, ‘Geronimo’, ‘Trust’, ‘Masada’ and ‘Buffalo’ tomatoes were resistant to leaf mold but were not vigorous. That lack of vigor combined with salt buildup in greenhouses reduced yields, so Colson started grafting for increased yield.

To graft, Colson starts rootstock and scion plants at the same time. He cuts each at a 45-degree angle with a razor blade, joins them with a silicon sleeve, prunes off cotyledons and part of the adult leaves and sets the plants in a plastic-covered tent to maintain a relative humidity above 60 percent. Ninety percent of the grafts take, leading to increased yield – sometimes twice that of nongrafted plants.

His grafted greenhouse tomatoes are indeterminate trellised plants trained to a single or double top. (His cherry tomatoes aren’t grafted.) When pruned to a single top and grown in a double row in a bed, with plants 14 inches apart within rows, each plant yielded 8 to 12 pounds of fruit; when pruned to a double top and grown 28 inches apart within rows; each plant yielded 15 to 18 pounds.

Typically, said Colson, an ungrafted plant would produce about 5 pounds of tomatoes. Since rootstock is expensive, double tops are worthwhile.

As plants grow, Colson prunes all fruit clusters to four fruits and prunes all leaves up to the first fruit cluster. When that’s ripening, he prunes up to the next cluster. This helps pickers see what’s ripe, seems to encourage exposed tomatoes to ripen faster, and creates better air flow.

To add potassium during the season in his organic system, Colson sifts wood ashes to remove charcoal, puts 5 pounds of sifted ashes in a grain bag, puts the bag in 50 gallons of water, lets it steep for three to five days, then applies that water with a watering can (without the rose attached) weekly, beginning when he sees the first flowers.

He gets about six weeks of “really good yield,” but after about eight weeks tomatoes start coming in so slowly that he takes the plants out of the house and has another planting ready to go. He has three staggered plantings in greenhouses, one field crop that comes in at the end of the summer, and one fall greenhouse crop.

Each year Colson leaves two of his four 17-foot houses open through winter to flush out salts.

Colson harvests into 20-pound boxes with lids that he gets from Paris Farmers Union. He suggests that those selling to wholesale markets grade and size tomatoes because “a lot of wholesale markets want a uniform size.” Colson noted that harvested tomatoes shouldn’t be held below 55 F.

Growing for wholesale brings less than retail, requiring greater production. A farm of 1-1/2 to 3 acres probably won’t have sufficient volume to sell wholesale, said Colson – unless only tomatoes are grown.

Colson presented the enterprise budget below for his greenhouse tomatoes, based on two beds, each 3 by 88 feet, with about 85 percent of tomatoes being grade 1. The two beds produce almost 1,500 pounds of grade 1 tomatoes.


Greenhouse Tomatoes, Variable Costs, Materials and Labor

Seeds/seedlings $230
Soil amendments 58
Soil tests 22
Black plastic/hay 41
Insect control 0
Disease control 0
Bed preparation 8
Trellis (3-year) 28
Irrigation 24
Transplant 48
Plastic removal 8
Harvest 145
Pruning/tying 192
Greenhouse (3-year) (for a fairly small structure) 1,000
Propane for heat 400


Total variable costs



Fixed costs (2 beds) (utilities, building repairs, insurance,
taxes, certification fees, etc.) 180
Total expenses $2,642


Tomatoes sold (85 percent of possible): 1,498 lbs.
@ $3.16/lb. average = $4,705 gross or $2,063 net

($3.16 is the average wholesale price to restaurants and natural food stores for the season; the range is about $3.80 to $2.65.)

@ $2.65/lb. average = $3,969 gross or $1,327 net

Colson calculated labor at $8 per hour and noted that pruning and tying takes 6 to 8 hours per week for several weeks. “Try to do this early in the morning when greenhouses aren’t so hot and it’s easier to work in there,” he said. He likes to have one person do just pruning and tying one day per week. “When I’m visiting farms, I see that it’s easy to put things in early in the season, but by the end of July or so, there’s so much to do that tomato tying may not get the amount of labor it needs,” said Colson.

Next Colson provided costs for growing two 92-foot beds in the field with slightly greater spacing than in the greenhouse, giving similar plant populations and growing area. His field-grown plants are determinate and are supported with a basket weave system. Two rows grow in each bed, with black plastic and hay mulch. Each plant yields about 5 pounds of fruit.

“We only market 50 percent of what’s out there,” said Colson, “which is why many of us have gone to greenhouse growing.”


Variable Costs, Field-Grown Tomatoes, Materials and Labor

Seeds/seedlings $ 29    
Soil amendments 118    
Soil tests 22    
Black plastic/hay 47    
Dipel/Entrust 33    
Disease control 0    
Field/bed preparation 8    
Stakes/twine 108    
Irrigation 8    
Transplant 48    
Plastic removal 4    
Harvest 213    
Covers (plastic) 94    

Total variable costs


Fixed Costs 180    
Total expenses $912    


Tomatoes sold (50 percent of possible): 795 pounds
@ $2.65/lb. average = $2,107 gross or $1,195 net
@ $3.16/lb. average = 2,512 gross or 1,600 net

Colson then provided a hypothetical budget based on applying a copper fungicide four times in order to harvest, potentially, 85 percent grade 1 tomatoes. Even at $2.65 per pound, the fungicide applications led to greater potential income.


Field Grown Tomatoes

Expenses $912
Copper fungicide (4 applications) $64
Total expenses $976





Tomatoes sold (85% of possible) 1,272 lbs.
Gross income @ ave. $2.65/lb. $3,370
Net income $2,394 (estimated)

“So the key seems to be management of field grown tomatoes,” said Colson. “Everything you can do to bring the harvest level up from 50 to 85 percent will help.”


Farmer Panel

Nate Drummond of Six River Farm in Bowdoinham grows (with Gabrielle Gosselin) mixed vegetables. He started growing only heirloom tomatoes, which was wonderful for marketing, but Six River is growing more red slicer hybrids now, which perform well and are in fairly good demand at fairly good prices at their markets.

“Everyone loves a few big beefsteaks mixed in with the display,” said Drummond, “but customers, for $4 per pound, seem to like three or four medium-sized heirlooms and one big centerpiece pound-and-a-half ‘Striped German’, for instance. So we’re always trying to find things that meet that 8- to 10-ounce niche.”

If tomatoes weigh only 4 or 5 ounces each, “we feel like we have to stick them in a pint container, because they get lost in the display.”

They grow a lot of cherry tomatoes, especially ‘Sun Gold’. They find that pints of all reds don’t sell as well as pints with mixed colors.

Drummond starts seedlings in flats on heat mats, which “make a huge difference.” Seedlings are pricked out into 50-cell trays, transplanted into 2-1/2-inch pots and fertilized with fish emulsion. Six River also sells transplants at farmers’ markets.

“If you’re going to sell transplants,” said Drummond, “sell plants that you know and are going to talk enthusiastically about, because people want to buy a transplant that they know you as a trusted farmer” like.

To minimize rototilling, Drummond prepares beds with a tractor, then puts a moveable tunnel over the bed. None of the Six River tunnels are heated, but a greenhouse where seedlings are started is heated. Plants are not grafted; they are pruned to a single leader.

Like other growers, Drummond had baling twine breaking last year. Dave Colson said the strength of baling twine has decreased because of round bales; others said one particular lot of twine was problematic last year.

Drummond transplanted into an unheated house on April 26 for production in the first week of July. He staggers plantings in tunnels to meet the higher demand early in the season and after mid-September; demand is lower between mid-August and mid-September, when home garden crops are producing. He has planted in the field and greenhouse during the third week of June for a late crop. Because disease pressure occurs more rapidly later in summer, he plants this late crop in a different part of the field. A drawback to late planting is that it moves pruning and trellising into a busier time of the year.

Landscape fabric controls weeds in the hoophouses.

Drummond brings bumblebees into the houses on the recommendation of his father, UMaine entomologist Frank Drummond.

Tomatoes are harvested into trays, in one layer, and are sorted and sent to market in the same trays. Cherry tomatoes are harvested into small buckets and then put in pints for market. Greenhouse tomatoes are harvested “almost dead ripe.”

Six River has grown a lot of field tomatoes, mostly heirlooms. They prefer to support them with rebar stakes and a basket weave system – a task that must be done on time or it takes much longer, so they assign a crew and a day to do this. They prune field tomatoes once but rarely after that. “It becomes a wall of tomatoes,” said Drummond.

This year Drummond grew only paste tomatoes in the field; and he bought new tunnels to attempt to move the flood of tomatoes from early August into July. He planned to sow and mow living mulches (barley or rye, clover, and alyssum for beneficial insects) outside, between rows of plastic.

Six River is moving away from mulching with straw because oats sprout from the mulch and because straw is getting harder to obtain.

Field-grown tomatoes are not harvested dead ripe. They sell for $4 per pound at the farmers’ market, where 80 percent of Six River’s tomatoes go.

After harvest, they remove the stakes, flail mow the plants and take up the plastic. The plants decompose over winter.

Septoria leaf spot and early blight are routine diseases, so they plant multiple successions and plan for the inevitability of disease instead of steam cleaning the house. Drummond thinks the shift to fruiting may make plants more susceptible to these diseases. He doesn’t use copper fungicides. “I don’t like handling it, and at the farmers’ market, it’s not something we would feel OK stating ... Kids grab cherry tomatoes and stick them in their mouth. I want to feel good that they can do that.”

Pete Engler and Sarah Trask of Small Wonder Organics in Bowdoinham grow produce, including tomatoes, sold through a CSA, by direct marketing and through a Tomato Passion Club that provides seven weeks of heirlooms. They seed tomatoes in 98-flats (1-3/8- by 1-3/8-inch cells) in a warm basement by a furnace and then move them to greenhouse spaced rented from another grower. Engler transplants into 4-inch pots, which adds organic matter to the field and gives a lot of leeway regarding the transplant date – generally late April to early May in a tunnel. Heirlooms are grown in double rows in 4-foot-wide beds; are pruned to a single or double leader, depending on the variety; and are attached weekly to a trellis on a 12-1/2-guage high tensile overhead cable wire.

This year Small Wonder’s heirlooms were all under cover, while four small plantings of paste tomatoes and of hybrid determinate red, orange and yellow tomatoes were grown outside, staked and basket weaved and not pruned.

Engler picks heirlooms at 40 to 70 percent blush, depending on the market and on how many people will handle them, and packs them in a single layer. He pruned some fruit clusters on beefsteak varieties this summer for more consistent production rather than two peaks of production with a trough in between.

Small Wonder doesn’t use black plastic because Engler has no way to put it down, prefers not to use it, and “a really good raised bed helps a lot” with soil warming.

They do use straw mulch, which, said Engler, has the added benefit of undersowing his tomato crop with a cover crop of oats.

Andrew Mefferd trials tomatoes at Johnny’s Selected Seeds, and he and his wife farm organic vegetable crops, eggs and lamb at their One Drop Farm in Cornville, near Skowhegan, selling at the Skowhegan farmers’ market, through a multi-farm CSA and through some small wholesale accounts.

He grows all large-fruited indeterminate tomatoes indoors, because by the time tomatoes start to ripen outdoors, it’s often getting cool again or blight hits; outdoors he grows a single row of determinate ‘San Marzano’ tomatoes, because “there’s a good market for sauce tomatoes later in the season” and growing determinates takes less labor. He also grew a single row of the determinate slicer ‘Defiant’ last year because of its resistance to late blight. ‘Defiant’ fruits are a little small. He also grows cherry and grape tomatoes in the field because they’re vigorous and early; they start producing around the same time as his hoophouse tomatoes.

Mefferd has two 30- by 48-foot unheated hoophouses from Nolt’s Produce Supplies, with 5-foot instead of 4-foot-high sides. Both ends have peak vents that open via a motor connected to a thermostat. He doesn’t have exhaust fans. He does have roll-up sides and top vents. He planned to hang two horizontal air fans from trusses in each house, one in each opposite corner, to move air within the house after noticing that tomatoes at Johnny’s didn’t get late blight because of horizontal air flow.

Tomatoes (half red slicers, half heirlooms) grow in one house, cucurbits in the other, alternating annually to minimize diseases.

Mefferd gets up around 5 or 5:30 a.m. to prune in the greenhouse, when suckers are turgid and easy to break off, and so that plants have the whole day to heal wounds. He removes suckers with an Exacto knife to minimize sites for botrytis to enter. To minimize disease spread, he does his greenhouse work before moving to field tomatoes; he changes clothes before going from home to Johnny’s, and vice-versa; and he sterilizes tools with rubbing alcohol when he goes into the greenhouse.

Last year he spread 15-foot-wide landscape fabric (also from Nolt’s) wall-to-wall in the house. It stood up all season and no weeds grew through it.

“It’s all about keeping the plant happy all the time,” he said. “Then it will perform to its highest potential.”

So this year he put 3-foot-wide landscape fabric between tomato rows and used drip tape instead of emitters. He thinks drip tape won’t clog, as emitters eventually may; and he can roll up the drip tape to put down compost. He planned to front-load compost before planting and then, when plants have their fifth flower cluster, roll up the drip tape, apply 4 to 5 additional gallons of compost per plant, then put the drip tape back down. The plants root into the compost and should remain vigorous throughout the year.

All plants are grafted, have double leaders and are set 2 feet apart.

Mefferd is trying to maximize yield and use of every square inch of his 1,440 square-foot houses. Last year he had five rows of tomatoes spaced evenly in the house, and he harvested a little more than 1 ton per house – about 30 pounds per plant from greenhouse types; 15 pounds from heirlooms. With that 7.2 square feet per plant spacing, he noticed some sunlight hitting the floor.

An old book suggested double rows 32 inches apart, with 48 inches between double rows.

“I realized you’d get the same population with single rows 40 inches apart,” so this year he was trying eight rows spaced 40 inches apart. With 160 double-headed plants (eight rows with 20 plants per row), each plant has 4.5 square feet. Cramming in more plants will reduce air flow and result in smaller fruit.

Last summer Mefferd used a timer to water plants, generally for four 15-minute intervals per day, and had almost no splitting.

He removes leaves up to the developing fruit cluster to help with air circulation; also, warmer fruits ripen faster, so this helps overall yields. Research in Holland shows that removing these leaves doesn’t reduce flavor.

Cluster pruning is important to maximize salable fruits, said Mefferd. ‘Brandywine’, for example, has clusters of about 20 flowers. Letting that many fruits grow will bog the plant down. He prunes beefsteak flowers to four per cluster, or waits until fruits are marble sized if there’s any chance flowers will abort before setting fruit. Heirlooms, especially, have huge fruit clusters, and often their first flower makes a huge, misshapen fruit, so that’s a good one to remove, said Mefferd.

Mefferd suggested trellising plants in the afternoon when they’re flexible. He clips stems to the string and supports fruit clusters with J hooks so that the fruit doesn’t pull from the stem.

Some of the higher tech greenhouse varieties are like divas, Mefferd said; they need a lot of pampering and won’t do well in the field.

Deer netting can keep birds out of the greenhouse – an important point, as One Drop Farm is getting HACCP (Hazard Analysis and Critical Control Points)-certified.

– J E


MOF&G Cover Fall 2012