Seed Stratification Guide
Downloadable PDF content.
Seed Stratification & Propagation Guide
Seed Stratification Information
Stratification information for individual seed species that we sell is listed in the "Cultural Details" section on the seed product page. The information is also available in PDF format, above.
Certain species have specific times of the season when they germinate best. Most wildflowers will exhibit higher germination when seeded in the fall. Cool season grasses and flowers, such as Junegrass, Prairie Dropseed, and Asters do best when planted in early spring when temperatures are cooler. Sedges also do better when planted in fall or early spring. If your goal is to establish both flowers and grasses together, it is best to plant in fall or early spring, provided that the site has been properly prepared and is free of weed problems. Information on when to seed, can be found here.
Dry straticfication is a seed pre-treatment in which the seed is subjected to cold temperatures of 32˚F or lower, for a period of a month or longer. This breaks dormancy in many native seeds, especially the prairie grasses and many prairie flowers. Some grasses have increased germination with moist stratification, but most will germinate well with only dry stratification.
All Prairie Nursery seed is “dry stratified” prior to shipping to help break seed dormancy.
Some seeds germinate best when seeded in fall, in a dormant seeding. The exposure to cold, damp conditions over the winter is a nature's "moist stratification," and signals to the seed that it is time to germinate when the soil warms up in spring. Some wildflowers need this process, more than others. A moist stratification seed treatment is used to mimic the effects of winter on the seed.
- Moist stratification is a process wherein the seed is mixed with moistened inert material and stored cold for ten days to three months. Many prairie wildflower seeds show improved germination with moist stratification, while prairie grasses generally exhibit little or no increase in germination.
- Planting the seed outside in the fall (direct seeding) achieves the same results as Moist Stratification. It is not necessary to use Moist Stratification pre-treatment for seed that is to be planted in the fall, as dormancy will be broken naturally in the soil over winter.
- To Moist Stratify seed: In a plastic bag or re-sealable container, mix the seed with an equal volume of moist (not wet) sawdust or clean builder’s sand (if moisture can be squeezed out of the sawdust or sand, it is too wet). Refrigerate at 34-38 degrees F (do not freeze!). Most flower seeds require three to four weeks of treatment. Legume seeds generally only require ten to fifteen days. Some flowers require two to three months.
- When planting moist stratified seed, it is best to water the area for one to two months after seeding. Though the seed is conditioned to germinate by stratification, it may revert to dormancy if it does not receive rain or moisture within a certain number of days after planting. All direct seedings in spring or early summer, pre-treated or not, will benefit from irrigation during the first two months after seeding.
Members of the legume or bean family can benefit from an inoculation with Rhizobium bacterium prior to planting. All of our legume seeds have been pre-inoculated with this bacterium. The bacterium works with the plant to form nodules, on the roots of legume plants, which are capable of taking nitrogen from the atmosphere and incorporating it into the plant.
Scarificatin of seed is the process of scratching the seed coat to allow moisture to enter the seed itself. Gently scratch the seed with a sandpaper block prior to planting or Moist Stratification. Many members of the pea family (legumes) benefit from Scarification.
Double dormant species have seeds that must spend two consecutive winters in the ground to break dormancy. These seeds are best planted in the fall, although they typically will germinate two years after being seeded in the spring.
Hot water is used for species that require heat to stimulate germination. Scarify the seed, then place it in a bowl. Pour boiling water over the seed and allow to cool. This mimics the effects of a prairie fire. Pour off the water, collect the seed, and Moist Stratify for 30 days as per directions above.