|You can start hundreds of native plants in a small area to create your own nursery. Heather McCargo photo|
By Heather McCargo
The traditional nursery industry has been following an ecologically destructive trajectory similar to the path of conventional agriculture. Most plants are mass produced using an arsenal of synthetic chemicals; many varieties are cloned or patented exotic species; and nursery outlets broker plants bought in, rather than propagating the plants themselves.
However, many people today want their yards and gardens to include species native to their region in order to provide habitat for native animals, including pollinators, and to function as part of their local ecosystem. This means they don’t want to have landscapes filled with cloned plants produced with poisonous chemicals. This creates the possibility of a niche market for nursery growers who produce native plants that are genetically diverse and free of synthetic chemicals.
While many traditional nurseries now offer some native species, they tend to focus on cultivars and hybrids. These are garden varieties that have been bred to have characteristics such as dwarfism, specific flower colors, double flowers, or variegated or purple foliage. To perpetuate these traits, the plants must be reproduced clonally, without sexual reproduction. The old-fashioned way to do this was through plant divisions or cuttings, and some Maine growers and suppliers still use these techniques. Increasingly, however, the bulk of today’s plants for the mass market are cloned in a laboratory through a sterile technique called tissue culture. And plant cultivars grown non-organically from seed are usually fed with a cocktail of fossil-fuel-based synthetic fertilizers and protected from insects with synthetic pesticides such as neonicotinoids, which are coated on seeds, taken up by the plants and become part of the plant tissue.
Double flowers or other garden traits may appeal to some people, but they lack the genetic diversity, reproductive ability and pollen supply that is necessary for plants and their pollinators to adapt to changing environmental conditions. If we want our gardens to support nature and play a role in preserving local biodiversity, we should include many wild-type native plants and grow them without harmful synthetic chemicals. (Of course if you are growing highbush blueberry or elderberry plants for fruit production, you may want to grow the larger-fruited cultivars.)
In the wild, most plants reproduce sexually, i.e., from seeds. Flowers are the reproductive organs of plants, and the insect pollinators assist in this process by transferring pollen between or among individual plants, creating genetic diversity. This genetic variation is a species’ best strategy for adapting to a future with a changing climate.
Seed propagation is the best way to maintain the genetic diversity in nursery-grown native plants. Below is a general plan for creating a native plant nursery.
Setting Up a Propagation Nursery
You don’t need expensive or sophisticated facilities to start propagating native plants. Seeds can be sown outdoors in nursery beds, flats or pots. Native plants are adapted to the fluctuating temperatures of our Maine climate. For many species, outdoor germination is often more successful than germination when seeds are sown in a greenhouse. Seedlings grown outside in good organic potting soil rarely suffer from the pests or damping-off commonly seen in greenhouse-grown plants. Seeds that need a cold period (stratification) to germinate can be sown outdoors in the fall; seeds that need no pretreatment to germinate can be sown outdoors in early spring. Seeds germinate when conditions are optimum for each species. You will quickly learn which seeds germinate in the cool or frosty temperatures of early spring and which wait until the heat of summer.
To create a nursery space, find a location with some shade that is separate from a major weed source, such as a field or weedy lot. A screen barrier can be erected to exclude weed seeds if this is your only option. Oak trees make an ideal canopy of shade for a native nursery. The north or east side of a building with a lath trellis also works well. If you plan to grow woodland species, you will need a nursery area with lots of shade. If you plan to grow meadow or wetland species, you want an area with at least half a day of sun to grow the plants on to a suitable size for sale.
You can start with a small area; a propagation bed or uncovered cold frame 5 feet wide and 12 feet long made of 2- x 10-inch stock will hold thousands of seedlings. Use a weed-free compost-based organic potting mix, not a sterile peat-dominated potting mix (which usually includes petroleum-based fertilizer). Either fill the frame with the potting soil or fill propagation flats or pots with potting soil and place them inside the frame.
Along with creating shade, protect your nursery from browsing deer, rabbits and squirrels (particularly if you plan to grow nut trees and shrubs). Deer fencing around the nursery is often necessary to exclude these browsers. To exclude squirrels that dig, attach rabbit wire screening to the bottom of the growing frame and make a wire screen lid for the top. Otherwise, they will dig in the seed flats and make a big mess. If your site is windy, planting a hedge or some other barrier to create a less windy microclimate will help plants get an earlier start in the spring.
Once you start moving seedlings into pots to grow on for sale, you will need more space for potted plants. For more details on seed bed construction, see https://wildseedproject.net/native-plant-propagation-techniques/.
Sowing the Seeds
Native seeds can be sown thickly and labeled with the name and date of sowing. A good rule of thumb is to sow seeds to the depth of the thickness of the seed and roughly 1/8 to 1/4 inch apart. Tiny seeds can be left uncovered. After sowing, cover the seeds with coarse sand. (This is preferable to covering them with potting soil, as the sand helps keep the seeds from splashing out in the rain.) If nearby weeds are a concern, cover flats with a spun-poly covering such as Reemay. Keep the planting medium watered (usually every couple of days to a week if flats are in the shade) and check regularly for germination.
To read more about native seed germination, see “Growing and Propagating Wildflowers” and “Growing and Propagating Native Trees, Shrubs and Vines,” by William Cullina; “Growing Trees from Seed,” by Henry Kock; and “Wild Seed 2015,” an annual publication of Wild Seed Project.
Waiting for Germination
Each native seed has its own timetable for germination. This is very different from cultivated plants such as vegetables and annual flowers that have been bred for rapid germination. Native seed germination typically happens over a period of weeks, months or even years, to help disperse offspring over time – a better strategy for plants in the wild.
In your nursery, seeds that are spring sown (milkweed, columbine, campanula, aster, goldenrod, Jack in the pulpit) will germinate from a week to several months after sowing. Species that need winter stratification (violets, foamflower, bunchberry, iris, elderberry, penstemon, blue vervain, Joe Pye weed) will germinate when the seed dormancy is overcome at the time appropriate to each species, typically from early spring to midsummer. Flats that fail to germinate in the first growing season often germinate the following year. Many native species take two years to germinate (viburnum, Solomon’s seal, lily, black cohosh). Don’t throw them out; be patient. If the un-germinated flats are in the shade, they will require little weeding or care.
Transplanting Seedlings into Larger Pots
Many native seedlings can stay in the original flat for the first growing season. If the seedlings seem overly crowded, they can be divided gently and potted on during the first summer. Otherwise, you can wait until the following spring to transplant seedlings to bigger pots. Don’t forget to keep the plants labeled. When transplanting, clump 3 to 10 seedlings together per pot (unless it is a tree species) so that each pot contains more than one individual for cross pollination. Applying diluted liquid seaweed fertilizer every other week will keep seedlings healthy and strong.
Winter Protection for the Nursery
Germinated pots and flats need winter protection from weather extremes and windburn, just as a consistent snow cover provides to a garden. Multiple layers of a winter-grade Reemay covered with white plastic work well. The plants should be frozen before being covered (in late November or early December); otherwise rodents may choose your covered nursery as their perfect nest site. Set mouse traps under the cover for additional protection. Griffin Greenhouse Supply (www.griffins.com) sells white Styrofoam insulating blankets for protecting nursery plants in winter.
Finding Native Seeds
Wild Seed Project is a Maine-based nonprofit that I founded to supply locally sourced native seed and to help educate the public about propagation techniques so that a wide variety of people can participate in increasing native plant populations. Visit the educational website for help getting started: https://wildseedproject.net.
These are other recommended sources of wild-type native seeds:
Native Haunts – www.nativehaunts.com
Project Native – www.projectnative.org
Prairie Moon Nursery – www.prairiemoon.com
New England Wetland Plants – www.newp.com
Collecting Your Own Seed
Collecting seeds of local native plants is an ideal way to promote the genetic diversity of your region. Remember that if you collect seed without having properly identified the species or researched how to handle the seed, you could damage native plant populations. Handling native seeds takes knowledge. For example, many woodland species have seeds that must be sown fresh immediately upon ripening. They will not be viable if allowed to dry out. Researching the propagation techniques for each species is very important for success.
Wild Seed Collection Procedures
1) Make sure you have properly identified the species when it is in bloom and you have checked with the Maine Natural Areas Program to ensure that the species is not listed as rare, endangered or protected. Visit the New England Wild Flower Society’s excellent online botanical key, https://gobotany.newenglandwild.org.
2) If you are not collecting on your own land, ask permission from the landowner before collecting seed. Collecting seed on public conservation land, national and state parks, and nature reserves is usually prohibited.
3) Research the germination requirements of each species before collection so that the seed is handled properly and not wasted.
4) Look for large, healthy populations of desired species and collect a small amount of seed from a number of individuals. If possible collect seed from several populations in the same region to minimize genetic drift or inbreeding depression. Make sure the seed is ripe before collecting.
5) Never collect more than 5 percent of the seed in any population. If the species you want has poor seed set or a small number of individuals, do not collect the seed.
6) Sow the seeds; do not waste them.
About the author: Heather McCargo is the director of Wild Seed Project, a Maine-based nonprofit working to promote the use of native plants. WSP sells locally grown seeds, publishes an annual magazine, Wild Seed 2015, and has an interactive website with lots of educational materials on propagating and growing natives at www.wildseedproject.net.