Germination & Seed Treatment

No pretreatment

This seed germinates readily once it’s sown into warm, moist soil, so no treatment is needed.

Cold-moist stratification

This seed needs a period of cold, moist conditions, in effect a winter, before it will germinate. The number of days it needs is listed on the species page.

The simplest and most reliable approach is to let winter do the work: sow the seed in late fall or winter onto a weed-free, firmed seedbed and leave it to overwinter outdoors. For a spring sowing, you can stratify the seed in a refrigerator instead:

1. Mix the seed with a moist medium such as clean sand, vermiculite, or a damp paper towel or coffee filter. It should be damp but not wet, so that you can’t squeeze any water out of it.
2. Seal it in a plastic bag labeled with the species and the start and end dates.
3. Refrigerate it, without freezing, for the number of days listed, checking every week or so that the medium hasn’t dried out or turned soggy.
4. Sow the seed when the time is up. If it starts sprouting in the bag before then, sow it right away.

Warm-then-cold stratification

This seed needs a warm, moist period (a summer) followed by a cold, moist one (a winter). Sown outdoors in spring or summer, it typically germinates the following spring. To speed things up, hold the seed in a moist medium at room temperature for about two to three months, then refrigerate it for another two to three months before sowing.

Double dormancy

This seed needs cold, then warm, then cold again before it germinates. Sown outdoors, expect it to emerge in its second spring or later, and avoid disturbing or replanting the bed in the meantime.

Scarify

A hard seed coat keeps water out until it’s weakened. Just before sowing, rub the seed lightly between sheets of medium-grit sandpaper, or nick larger seed with a blade, stopping before the seed itself is damaged. If the species also needs stratification, scarify it first. Seed that’s being sown in fall or winter generally doesn’t need scarifying, because freeze–thaw cycles do the same job.

Hot-water soak

A hot-water soak is another way to soften a hard seed coat. Pour water that’s just off the boil over the seed, let it cool and soak for about 24 hours, then drain it. If stratification is also listed, stratify the seed afterward.

Surface sow (needs light)

This seed is either very small or needs light to germinate, so it should stay at the surface. Press it onto the soil and cover it with no more than a dusting of soil, then keep the surface from drying out until the seedlings are established.

Sow fresh (do not dry)

This short-lived seed loses viability if it dries out. Keep it refrigerated and slightly moist, and sow it or start its treatment as soon as you can.

Best fall-sown

These species respond best to overwintering naturally outdoors, and artificial stratification is less reliable for them.

Prefers cool soil

This seed germinates best in cool soil, so sow it in late fall after a hard frost, or in early spring.

Legume (rhizobia)

Legumes, members of the pea family, form partnerships on their roots with rhizobia bacteria that fix nitrogen from the air. These bacteria occur naturally in most soils, so an inoculant usually isn’t necessary, though it can help on heavily disturbed or sterile ground.

Hemiparasite (needs host)

A hemiparasite makes its own food through photosynthesis but also taps into the roots of neighboring plants, so it needs a host to establish. Sow it together with, or into existing stands of, low-growing grasses and sedges such as Little Bluestem or Pennsylvania Sedge.