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Seed Stratification Codes



A. Seeds should germinate upon sowing in a warm location. No pre-treatment necessary other than cold, dry storage.


B. Hot water treatment. Bring water to a boil, remove from heat, pour over seeds, and soak in a warm place for 24 hours before planting.


C. (Number of stratifying days.) Seeds germinate after a period of cold, moist stratification (such as in the spring when the snow melts). Mix seeds with equal or greater amounts of damp sand or vermiculite or other sterile media. Moist, but not so wet that water squeezes out of a handful. Place mixture in a labeled, sealed plastic bag and store in a 33-38 degree refrigerator for the number of days indicated in parentheses. Example: C(30) indicates the seeds should be stored in the above manner for at least 30 days.

*If sprouting occurs, plant immediately.

*You do not need to use this method if planting in the fall.


D: Seeds are very small and/or need light to break dormancy and germinate. When sowing seeds requiring this method, sprinkle on top of the soil, or use a light dusting of soil to cover the seeds. If grown in outdoor beds, sow seeds (previously stratified, if necessary) on a level surface and cover with a single layer of burlap or cotton sheet. Remove cover after germination. Do not let soil dry out until seedlings are established. If sowing seeds in containers, warter from the bottom as needed.


E. In order to germinate, seeds need a warm, moist period followed by a cold moist period. Mix seeds with sterile media, place in a labeled, sealed plastic bag and store in a location approximately 80 degrees for 60-90 days. Then place in a 33-38 degree refrigerator for 60-90 days.

*If sowing outdoors, you can skip this step but you must allow a full year for germination.


F. Seeds germinate after a cold, moist period, followed by a warm, moist period, followed by a 2nd cold, moist period. Follow instructions for code C for 60-90 days, then store in a location approximately 80 degrees for 60-90 days, followed by a second code C treatment.

*If sowing outdoors, you can skip this step, but you must allow two years for germination.


G: Seeds germinate best in cool soil. Sow in late fall after a hard frost, or in early spring.


H: Seeds need scarification. Scarify seeds by rubbing them between two sheets of medium grit sandpaper. Lightly erode the seed coats without crushing the seeds. If another form of stratification is also required, scarify the seed first.


I: Legume, Rhizobium Inoculum. Add inoculant to dampened legume seeds and mix thoroughly at time of stratification. Or, if direct seeding, mix as close to planting time as possible. Protect inoculated seed seeds from sunlight and drying winds. Cover as quickly as possible with a light coating of soil or mulch. Inoculum can also be mixed with potting soil for planting in pots, flats or directly transplanting.


J: Hulls should be removed from legume seeds for greatly improved germination. Treat as

 in code H.


K. Parasitic species that require a host plant. With a knife, make a 2” long cut at the base of the host plant, about 1/8” deep. Sow seed directly into the cut. If host plant is being transplanted at the sowing time, the cut is not needed and the seeds will attach to the damaged roots of the host plant. As another option, try sowing seeds from parasitic species at the same time as sowing seeds of the host plant. To add parasitic species to existing sites, scatter seed on the soil surface. (rake in if the seeds are large) in late fall.

*Little Bluestem, Penn Sedge, June Grass, Hairy Grama and Blue Grama are all acceptable host plants.


L: Plant fresh seed or keep moist. Refrigerate until planting or starting other treatment.


M: Best planted outdoors in the fall.




Stratification: Stratification is the process of pre-treating seeds in order to stimulate natural conditions that seeds would experience in the soil over winter.


Scarification: Weaking, opening or otherwise altering the seed coat to encourage germination.


Rhizobium Inoculum: A bacteria applied to legume seeds (clover, peas, beans, etc…) before planting. Legumes are “nitrogen fixers,” meaning they can take nitrogen out of the air and return in to the soil, but they can’t complete this process without the inoculant.


Nitrogen Fixers: Plants that help convert atmospheric nitrogen into a form that can be more ready utilized by plants. Examples include clovers, peas, lupines, black locust trees, partridge pea, redbud trees, baptisia species, and others. 


Dormancy: The condition in which a seed is unable to germinate. Dormancy can be broken by offering ideal growing conditions or by intentional stratification processes as mentioned in the chart. Seeds remain dormant until conditions are favorable for germination.


Germination: The process by which a seed starts growing into a seedling, essentially the process of seeds developing into new plants.





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1 Comment

Michelle Bradley
Michelle Bradley
Apr 06

Silly question but so very curious - grape seeds for example have a less than 10% propagation/sprouting rate and some theories this is because a grape seed must pass through the digestive system of a mammal or bird as part of its stratification process. What steps would we take to make more grape seeds grow?

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