Germination Codes

Germination codes and their definitions**

A.  No pre-treatment necessary other than cold, dry storage (also called dry cold stratification).  Seed should germinate upon sowing in a warm location. When seeds are purchased from a native plant nursery, they have likely been stored under these conditions and should not require further treatment before sowing.

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.  Please note: You do not need to stratify if you are fall planting.  Also, do not use this method if you are planting a seed mix and cannot keep the site moist.  Mix seeds with equal amounts or more of damp sand, vermiculite, or other sterile media (moist—but not so wet that water will squeeze out of a handful).  We use silica sand (purchased at a building supply center) for small quantities.  For large quantities we use coarse grade vermiculite.  Place mixture in a labeled, sealed plastic bag and store in a refrigerator (33 – 38 degrees F). Stratify for the # days indicated in parentheses.  If two months (C(60)) of this cold storage before planting is normally required to break the dormancy of these seeds, one month may work for many species if time is a constraint.  Some seeds may sprout in the storage bag if moist stratified too long.  If sprouting occurs, plant immediately.   Another method of breaking dormancy for species requiring moist stratification is to sow seeds outdoors in the fall so they may overwinter.

D.  Seeds are very small or need light to naturally break dormancy and germinate.  Seeds requiring this treatment should be surface sown – no soil cover or just a dusting of soil should be applied.  If grown in outdoor garden beds, sow stratified (if required) seed on level surface.  Cover with a single layer of burlap or cotton sheet.  Remove cover after germination.  Do not let soil dry out until seedlings are established. Shading with a window screen set 12” above soil the first year will help prevent drying.  If sowing seeds in containers, water from the bottom as necessary.

E.  Seeds need a warm, moist period followed by a cold, moist period.  Seeds need a warm, moist period followed by a cold, moist period:  Mix seeds with sterile media.  Place mixture in a sealed plastic bag in a warm place (about 80 degrees F.) for 60-90 days.  Then place in the refrigerator for another 60-90 days before sowing.  Another method is to sow outdoors and allow one full year for germination.

F.  Seeds need a cold, moist period followed by a warm, moist period followed by a 2nd cold, moist period. Seeds germinate after alternating cold moist, warm moist, cold moist stratification treatments.  Start by following instructions for code C for 60-90 days, then store in warm (about 80 degrees F.) place for 60-90 days followed by a 2nd cold, moist period in the refrigerator.  Another method is to sow outdoors and allow 2 years or longer to germinate.

G.  Seeds germinate most successfully in cool soil.  Sow seeds in late fall (after hard frost) or early spring.

H.  Seeds need scarification.  To scarify, rub seed between 2 sheets of medium grit sandpaper.  The goal is to abrade seed coats – stop if seeds are being crushed.  Scarification should be done before stratification (code C), if needed.  It is primarily important to scarify seed that is to be planted in spring.  Seed that will be planted outdoors in fall should not be scarified to avoid premature germination and winter kill.

I.  Legume, Rhizobium Inoculum.  Inoculum aids in the fixation of atmospheric nitrogen and improves the long-term health of native plant communities.  Inoculum will keep refrigerated for approximately one year.  Add inoculant to dampened seed and mix thoroughly at time of stratification (code C) or if direct seeding, as close to planting time as possible.  Protect inoculated seed from sunlight or 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 or flats, or directly into transplanting hole.

J.  Legume seed with hulls.  Your supplier may remove hulls from this seed before sale.  This gives more seeds per pound and greatly improves germination.  If you have unhulled seed, treat as in Code H.

K.  Hemiparasitic species which needs a host plant.  Good hosts for many parasitic species include low growing grasses and sedges—Hairy or Blue Grama, Little Bluestem, June Grass, Common Oak Sedge.  With a knife, make a 2” deep cut at the base of the host plant.  Sow seeds in the cut, making sure it is not more than 1/8” deep. If the host is transplanted at sowing time, the cut is not needed; damaged roots will be available for attachment by the hemiparasite.  You may also try sowing seeds of the host and parasitic species together.  To add hemiparasitic species to existing sites, scatter seed on soil surface (rake in if seed is large) in late fall.

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

M.  Best planted outdoors in the fall. 

S.  Fern spore sowing.  Sow fern spores on sterile peat under glass in indirect light.  Water with distilled water.  Refer to other reference material on growing ferns.  Or, direct sow spores on soil surface.

**NOTE:  Germination codes and their definitions are supplied courtesy of Prairie Moon Nursery.  The nursery compiled these codes from available literature, their own experience, and feedback from other growers and customers.