By Jean English
Dave Colson of New Leaf Farm in Durham, Maine, shared his expertise in growing cole crops at a MOFGA-sponsored talk at the Maine Agricultural Trades Show in January. He pointed out that broccoli and cauliflower can diversify the type of labor required on a farm, because each plant can be harvested only once (assuming broccoli hybrids that produce a single, main head are used), as opposed to salad mixes, which are harvested frequently. “You don’t gross as much per acre” with cole crops, said Colson, “but there’s much less harvesting, washing and prep work than with salad crops.”
Colson promotes cole crops not just for their taste but for their superb nutritional qualities as well. “There’s more vitamin C in 100 g of broccoli than in an equal amount of orange juice,” he said, adding that broccoli contains such cancer fighting substances as carotene, indoles and others.
Broccoli and cauliflower do best with cool temperatures, especially cool nights, said Colson. “They handle heat in the daytime as long as they get a cool-down at night. Hot weather tends to make the heads ‘rice’” – i.e., the flower buds separate. The crops have 2- to 2-1/2-foot-deep root systems, so they need loose soil and plenty of water. They require a pH of 5.5 to 6.5 and a “fairly high” amount of calcium, as well as nitrogen and potassium. “They’re fairly heavy feeders,” Colson said.
Colson seeds his broccoli every two weeks, from mid-March to the first week in July, in 200-cell styrofoam flats that are set on benches in his solar greenhouse. Heat tape under the flats keeps them at about 70 degrees F, and a plastic tent pulled over the flats at night keeps that heat near the plants.
After germination, the plants are moved to other benches, where they do not receive so much heat at night. This results in stockier plants. A few weeks later, they are moved to cold frames, where they spend about a week; the first transplants go into the field in late April.
Cauliflower is raised only for a fall crop. “It doesn’t mature well in hot weather,” Colson explained. Heat and a lack of moisture prevent the crop from developing well, and it goes by too fast in the summer. Also, Colson has found that customers want zucchini, cucumbers and other such vegetables in the summer, but they want the hardier types of vegetables in the fall. Cauliflower is started at the end of April or in early May, and Colson makes two or three plantings of cauliflower to stagger the harvest. Transplants are set in the field in June.
Both broccoli and caulifower are transplanted into 4-foot-wide beds that are 200 feet long. These beds have had a green manure plowed into them, as well as rock phosphate or bone meal; sul-po-mag or other amendments are also added as needed. The beds are topdressed with about 8 pounds of bloodmeal per 200-foot bed to give a boost of nitrogen, particularly in the spring, when N is not so readily available.
The transplants are set in the soil by hand, as workers ride on a tractor-pulled transplanter. A shank opens a furrow, and the workers set the plants two hands, or 16 inches, apart. Colson spread the fingers of his hand to show that the distance from the tip of the thumb to the tip of the little finger is about 8 inches. The rows are 30 inches apart, with two rows per bed. Seventy plants fit in a hundred-foot row, so a 200-foot bed holds 280 plants. It takes 15 minutes to plant one bed. The plants are watered in by hand.
Beds of broccoli are alternated with beds of lettuce. “A double row of broccoli and a lower bed of something else, such as lettuce, improves air flow and reduces diseases,” Colson said. Also, it is easier to spray the broccoli with Bt without damaging neighboring broccoli when beds alternate, since the tractor can be driven over the lettuce bed to spray the broccoli. Likewise, harvest is simplified, since the lettuce has been picked by the time the broccoli is ready.
Broccoli and cauliflower beds are covered with Reemay as soon as they’ve been planted. Not only does the material deter insects, but it helps push the crop by increasing temperatures slightly early in the season. Cultivation can be difficult, because the Reemay has to be pulled up, but by using a set of disks on the tool bar behind the tractor and supporting a roll of Reemay above the disks, the disks can open the furrows for the sides of the Reemay. People walk alongside the beds, kicking the soil in over the edge of the furrow as the Reemay is put down. Colson cultivates about three weeks after transplanting with a basket cultivator, puts the Reemay back on, then may remove the Reemay again and use a shank cultivator later.
Irrigation is important, especially when the transplants are first set, and again when they begin to flower.
Colson next discussed pests of cole crops. Black leg, he said, is a fungal dry rot that tends to be seed-borne. It causes small, black spots that expand into round, brown discolorations. The leaves eventually wilt or turn bluish or red. The spores are spread by splashing of rain or dew. Buying hot water treated seed can prevent this problem. (Seed is treated with 122-degree water for a short period by the seed company.)
Black rot is a bacterial infection that appears first on the leaves as a yellow, wedge-shaped area, while the veins become darkened. The leaves later wilt. Plants may not produce heads if the disease strikes early; if it occurs later, when the plants are heading, the heart of the head may not develop and/or it may get an area of rot in it and a rotten smell to it. “This can be a problem for marketing if you don’t catch it,” said Colson. Black rot can be carried by aphids or other insects, or by splattering of rain or surface water. The bacteria live in the soil or on the seeds. Hot water treated seeds can help, as can clean cultivation, eliminating especially wild crucifers. Rotating for at least three years can help; and spacing plants to maximize air movement “is the biggest thing that’s helped us,” said Colson. Be careful with watering, too, he added. Insufficient water can stress the plants and create conditions for black rot to thrive, while overwatering can also be harmful.
Club root has not been much of a problem at New Leaf Farm. It is a fungal disease that is not seed-borne. It causes yellowed, then wilted leaves, but the veins do not become darker as in black rot. The roots become enlarged and misshapen. To prevent club root, use healthy seedlings; control cruciferous weeds; maintain the proper pH (acidic soil makes the problem worse); and rotate out of crucifers for at least seven years if the problem occurs.
Rhizoctonia attacks young tissue and can cause damping off or wire stem of seedlings. “Don’t move affected plants into the field,” said Colson.
Regarding insects, Colson said that aphids had not been a big problem at New Leaf. When they are problematic, it’s mostly on seedlings. “Last year they came from a parsley plant that overwintered in the greenhouse,” so keep your greenhouse clean, he advised.
Cabbage maggots cause plants to wilt. The adult is like a house fly, but smaller (about 1/3 of an inch long). It lays its eggs near the base of the plant, in the soil, and the maggots then burrow into the roots. “In areas where we hadn’t done anything, we got 50% loss,” Colson reported, and the plants that survived did not produce well. Reemay is the best maggot deterrent for New Leaf Farm, especially in late May and early June, when the fly and maggots do the most damage. While another generation may occur later, “late May and early June are really the critical times. We don’t get enough root maggot damage by late June to require covering with Reemay for the fall crop.”
The three Lepidopteran pests, the cabbage worm, imported cabbage worm and cabbage looper, are controlled with Reemay early in the season, then are sprayed with Bt on a 7- to 10-day schedule. Colson has found that “if Bt has been on and dry for about an hour before it rains, it is about 90% effective,” even though he does not use a sticker. “Unless there’s a dramatic amount of rain over a week, it’s pretty effective.” One problem with spraying Bt is that, due to Worker Protection Standards, workers cannot reenter the field for 12 hours after the application. “So all of the spraying has to be done in the evening, which may not be the best time.” Colson says he tends to spray his cole crops right after harvesting the previous crop, so that the longest period occurs between spray and harvest and marketing.
Flea beetles are controlled with Reemay, and clean cultivation helps control cutworms – which haven’t been much of a problem at New Leaf.
Cole crops are harvested in the cool of the morning at New Leaf. The crops are often watered the day or night before harvesting, so that they have sufficient moisture in them and the heads stand up better.
Broccoli is harvested with a 4- to 6-inch stem attached, and the leaves are pulled from the stalks. While harvesting, “We’re constantly watching for black rot,” Colson said. They harvest into sturdy plastic field boxes, which are put directly into a cooler until they are ready to be packed. The field boxes are covered with damp towels while they are in the cooler, because “the cooler is the right temperature but it sucks moisture out of produce.”
While some growers immerse broccoli in cold water before packing it, New Leaf doesn’t. Colson said that growers could make a salt water brine both to cool plants and to clean worms from them “if you have a lot of worms.” Most of the big growers, he said, pack their broccoli in ice or an ice slurry; New Leaf does not. “We pack into wax boxes, then put them back into the cooler with damp towels on them. They go right into coolers” at the retail outlets, also. Each box holds about 16 pounds of broccoli, which sells for $1.50 to $1.60 per pound, so each bed brings $300 to $350.
Most of the cauliflower varieties that New Leaf grows are self blanching, and they mature best in cool weather. “You have to check almost daily to see which [head] is ready,” said Colson. Those that are ready are cut without a stem, and care is taken not to touch the curd, because the oil on the skin can make the heads brown over time. Some leaves are left on, but not enough to cover the head.
Cauliflower is packed, unwashed, into boxes, in a single or at most a double layer, then is moved to the cooler.
After fall cole crops are harvested, Colson tries to get something growing in the field to hold the soil over winter. “Rye or oats work well for us,” he said.