by Pat Lewis
Question: How do you start native plant seeds indoors? I've heard words like stratification and scarification. What do they mean?
Answer: To find out how to start native plant seeds indoors, I consulted Steve Keto of Nesta Prairie Perennials, Jewel Richardson, a Wild Ones member and owner of Wetlands Nursery, and Vicki Gagne, one of our members and a long-time gardener.
Many growers just sow their native plant seeds outdoors in the fall. However, for those who need or prefer to start seeds indoors, here is what you do.
Starting native plants indoors from seed is pretty much like starting any other garden seeds, except that most native seeds from this part of the country need some kind of cold treatment (called "stratification") before they are planted, in order to mimic natural winter conditions and encourage germination.
Some seeds are satisfied with cold, dry storage, but many others need cold, moist storage. Cold, moist storage involves mixing the seed with a dampened medium such as coarse sand, sawdust, or vermiculite. The mix can then be put in a plastic bag and stored in the refrigerator. A common length of time for cold, moist storage is 60 dayshowever, this requirement is different for each plant species. (Note: If the seeds start to sprout, plant them immediately.)
Since seed treatment requirements vary widely, it is very important to have some kind of native plant seed-starting manual to refer to. Steve Keto of Nesta Prairie Perennials recommends Growing and Propagating Wildflowers by Harry Phillips. Jewel Richardson, owner of Wetland Nursery and one of our members, suggests Collecting, Processing, and Germinating Seeds of Wildland Plants by James A. Young. Both growers agree, however, that the Prairie Moon Nursery catalog has excellent "in-a-nutshell" information on native seed germination. The catalog explains different germination techniques and then assigns a germination code to each plant species. To get this free catalog, download it from their website at prairiemoonnursery.com/catalog.html or call (507) 452-1362. (Another excellent catalog, although it lacks the same type of germination information, is from Prairie Nursery. It contains excellent pictures and species information. Call 1-800-476-9453 for a copy.)
In addition to cold stratification, some seeds have extra preferences. Legumes such as lupine and native clovers may show better germination if watered with an innoculant after root growth starts. (An innoculant is a microorganism that promotes root growthand each plant species takes a different one.) This is not as troublesome as it sounds, however, since innoculants are inexpensive and easy to apply. Just mix with water and use to moisten the soil in the seed flat. Although innoculants are not strictly necessary, they may provide a good boost for your seedlings. Innoculants can be ordered from Prairie Moon Nursery.
Another requirement of some seeds is "scarification." These seeds have very large, hard seed coats which need to be nicked or scraped or otherwise broached so the seed can contact the soil and moisture. The Prairie Moon catalog suggests rubbing these seeds between two pieces of medium-grit sandpaper to weaken the seed coat. Steve Keto says you can also just nick them with a knife. Scarification should be done before cold, moist stratification.
Once your native seeds have been pretreated (if necessary), they can be planted like most other seeds. Vicki Gagne recommends a good-quality potting soil such as Peters, which she buys at Arrowhead Nursery. Making sure the soil is thoroughly moist and free of dry spots, spread it in seed flats and sprinkle the seeds over the top. Cover seeds lightly with soil (no deeper than the seed diameter is a good rule of thumb). Cover, keep moist, and check daily for germination. Once the seeds sprout, put them under fluorescent lights (about 2 inches distant) to keep them from getting leggy. (Vicki says plants get better light this way; putting them in a window may not be enough.)
When seedlings have their first true leaves, transplant to small pots or cells. When they look big enough to hold their own and when weather and soil have warmed up, plant out in the garden. Since most natives are warm-season plants, it is important not to put them out too early. Late May to early June, or even later, is good timing. With this in mind, figure carefully to avoid starting them too early (January is too early for most species).
Also, don't move seedlings directly from the house to the garden. Give the seedlings a two-week "hardening-off" period, during which they are gradually moved from shade to increasingly sunny locations.
For more detailed seed-starting information, Jewel Richardson recommends Seeds by Peter Loewer, and The New Seed Starters Handbook by Nancy Bubel. Another excellent native plant germination book is The Tallgrass Restoration Handbook by Stephen Packard and Cornelia Mutel.