GERMINATION CODES FOR PERENNIALS
Purpose and Scope
Prairie Moon Nursery assigns germination codes to native seed packets and catalog listings. The codes describe dormancy-breaking treatments, sowing conditions, and special biological requirements. They are especially useful for perennial native plants, whose seeds often wait through one or more seasonal cycles before germinating.
Important: Use the code printed on the exact seed packet or current species listing. Codes may be combined, and the species-specific listing overrides this summary.
Complete Code Reference
Code | Meaning | What to do |
|---|---|---|
A | No pretreatment | Sow in a warm location; seed should germinate without dormancy treatment. |
B | Hot-water treatment | Boil water, remove from heat, pour over seed, soak 24 hours at room temperature, drain, then continue with Code C when assigned. |
C(#) | Cold-moist stratification | Keep seed damp—not wet—at 33–40°F for the number of days in parentheses; C(60) means 60 days. |
D | Surface sow / light needed | Do not cover, or apply only a dusting. Maintain surface moisture; bottom-water containers. |
E | Warm-moist, then cold-moist | About 80°F for 60–90 days, then 33–40°F for 60–90 days; outdoor spring sowing may take a full year. |
F | Cold-warm-cold sequence | Cold-moist 60–90 days, warm-moist 60–90 days, then a second cold-moist period; outdoor germination may require two years or longer. |
G | Cool-soil germination | Sow outdoors after a hard frost in late fall or in early spring. |
H | Scarification | Abrade the coat with medium-grit sandpaper without crushing seed. Do before Code C when both apply; do not scarify fall/winter-sown seed. |
I | Legume / rhizobia note | A pea-family plant. Genus-specific inoculum may aid long-term nitrogen fixation, although compatible rhizobia occur naturally in many soils. |
J | Dehulled legume seed | Prairie Moon removed hulls to improve germination. Dehulled seed obtained elsewhere is treated as Code H. |
K | Hemiparasite needs host | Sow at or near suitable host roots, no deeper than 1/8 inch. Low grasses and sedges are often useful hosts. |
L | Plant fresh or keep moist | Do not dry-store. Refrigerate until planting or until another assigned treatment begins. |
M | Fall outdoor sowing best | Artificial stratification may be unreliable; expose seed to natural outdoor conditions. |
O | Impermeable coat | Nick the seed coat carefully and soak overnight before planting. |
? | Requirements uncertain | Prairie Moon reports that the best germination method is not yet certain and welcomes grower observations. |
How to Read Combined Codes
Packet code | Plain-language reading | Practical sequence |
|---|---|---|
C(60), D | Cold-moist period plus light-sensitive sowing | Stratify damp seed 60 days at 33–40°F; then surface-sow and maintain moisture. |
H, C(30) | Scarify, then cold-moist stratify | Abrade the coat first; then refrigerate damp seed 30 days before sowing. |
C(60), G, M | Cold requirement; cool soil; fall sowing preferred | The simplest route is shallow outdoor sowing in late fall and letting winter supply Code C. |
L, E | Keep fresh seed moist; warm then cold sequence | Prevent drying, then give warm-moist followed by cold-moist conditions. |
K, C(60) | Host plant required plus cold-moist period | Stratify first, then sow shallowly beside a suitable host or sow host and hemiparasite together. |
Preferred Method for Beginning Perennial Growers
- Prairie Moon recommends natural outdoor stratification for newcomers: surface-sow on a bare, weed-free, compact site in late fall and allow seed to overwinter.
- Sow shallowly—Prairie Moon advises no deeper than the width of the seed. Code D seed remains at the surface.
- Label each species and code. Record sowing date, seed source, treatment, location, and emergence.
- Protect seedbeds from weeds, rodents, drying, erosion, and disturbance. Water periodically while seedlings establish.
- Do not discard a well-managed perennial seedbed after one season. Some species germinate during the second year or later.
Artificial Code C Protocol
1. Calculate the refrigerator start date from the sowing date and the C-number.
2. Briefly wet the seed, drain completely, and arrange it in a single layer in damp paper, coffee filter, fine sand, vermiculite, or another horticultural medium.
3. The medium must be damp but not soggy; no water should squeeze out.
4. Seal in a labeled bag with species, code, start date, and target finish date. Refrigerate at 33–40°F—never freeze.
5. Inspect weekly. Prevent drying and excess moisture; replace paper when necessary.
6. Plant immediately when the stated period ends or if substantial sprouting begins in the bag.
Perennial Examples
Perennial | Prairie Moon code | Interpretation |
|---|---|---|
Big Bluestem — Andropogon gerardii | A | No pretreatment; sow when conditions are warm. |
Golden Alexanders — Zizia aurea | C(60), G, M | Cold-moist stratification; cool-soil germination; fall outdoor sowing preferred. |
Prairie Smoke — Geum triflorum | C(60), M | Cold-moist stratification; fall outdoor sowing preferred. |
Wild Ginger — Asarum canadense | L, E | Keep fresh seed moist; then warm-moist followed by cold-moist conditions. |
Frequent Errors
- Treating combined codes as choices. Unless Prairie Moon says otherwise, every listed code supplies part of the protocol.
- Confusing cold-dry storage with cold-moist stratification. Code C requires both cold and moisture.
- Using a freezer. Code C calls for refrigerator temperatures of 33–40°F.
- Making the medium wet enough to squeeze out water. Excess water reduces oxygen and encourages decay.
- Burying Code D seed. Small or light-sensitive seed must remain at or very near the surface.
- Giving up after the first growing season. Codes E, F, and some naturally sown perennials may require extended seasonal cycling.
- Scarifying winter-sown Code H seed. Prairie Moon warns this may trigger premature germination and winter injury.
Working Record
Species / lot | Codes | Treatment dates and conditions | Outcome |
|---|---|---|---|
Source and Date Checked
Primary source: Prairie Moon Nursery, “How to Germinate Native Seeds” and its Germination Codes & Instructions. Checked 2026-08-25. https://www.prairiemoon.com/how-to-germinate-native-seeds.html
Examples were checked against Prairie Moon’s current Big Bluestem, Golden Alexanders, Prairie Smoke, and Wild Ginger listings. Prairie Moon developed the summarized code system; this independent Information Sheet is not an official Prairie Moon publication.