GENERAL RULES of SEED SOWING

Seeds need water and oxygen to germinate, so are best started in a light, loose soil that will not compact, get soggy, or crust over. Free flow of water & air are a must. Cover seed with 2 - 4 times their thickness of soil, unless they require light to germinate. Sow shallowly in cold wet spring, more deeply in warm dry summer. Large seed can be soaked overnight and planted singly. Barely cover small seed, and sprinkle fine seed on the surface and water by misting. Plant flat seed edgewise and winged seed with wing uppermost or broken off. Sowing too thickly wastes seed and weakens the crowded seedlings, but some kinds sprout best if crowded. Lightly tamp soil to insure good contact with the seed, unless heavy. Keep soil moist, not soggy, and do not allow to dry out.
Common causes of failure are soil too heavy, wet or cold, or allowed to dry out, not giving slow seeds long enough to come up, pests eating the seeds or seedlings, and not giving dormant seeds the proper pretreatment. Common causes of seedling loss are damping off due to poor air circulation & overwatering, drying out or burning due to placing in full sun or outdoor conditions too quickly, transplanting shock (best done on a cool, moist day), and predation by insects, slugs and snails at night.

TEMPERATURE

Most seeds germinate best at warm (70°F) temperatures. Plants from temperate regions, the arctic, high mountains and high deserts often germinate best at cool temperatures. Plants from areas like California, the Mediterranean, Chile, S. Africa and parts of Australia also like cool temperatures. Warm temperatures will often speed germination of these seeds, but lower vigor & survival. Warm desert plants and tropicals like warmth. Temperatures used are: Cold (34 - 45°F), Cool (50 - 65°F), Warm (65 - 80°F) and Very Warm (80 - 100°F). When no temperature is given, warm (70°F average) .

HARDY ANNUALS (HA)

These will stand some frost and can be sown direct to the garden as early as the ground can be worked, March to June. Prepare the soil until a smooth, fine surface is obtained. An attractive annual border can be had by planting in large, irregular drifts.

HALF HARDY ANNUALS (HHA)

These are killed by frost and should be sown in late spring after danger of frost. For early bloom, start early indoors & plant out after danger of frost.

TENDER ANNUALS (TA)
These need warmth and shelter and are best started in pots or flats and planted out in favored spots after the soil has warmed.

BIENNIALS
Biennials are sown like half hardy annuals or perennials in spring or fall and planted out in September and October.

HARDY PERENNIALS (HP)

Many of these germinate readily at warm temperatures, and can be sown direct to the garden or early in the greenhouse or cold frame. If started early, they often flower the first year. Others germinate best at cool or cold temperatures and the seedlings need cool temperatures. Many have various dormancies & need the pretreatment indicated.

HARDY TREES & SHRUBS

Many will germinate readily if sown in spring. Others need cold or other pretreatment, and some are best sown in autumn or winter and covered with a mulch or snow. The addition of some forest soil or litter from below both hardwoods and conifers is often very beneficial, greatly increasing seedling growth due to beneficial mycorrhizal inoculation.

TROPICAL & SUBTROPICAL PLANTS

These often need very warm temperatures. Bottom heat and constant moisture are often beneficial. Some take surprisingly long times to germinate.

FERN SPORES

Spores should be scattered thinly on the surface of a light, sterile, peaty mix which has been watered with clean sterile water about 4 hours before sowing. Cover pot with a pane of glass or enclose in a plastic bag and place out of direct sunlight. A light green film will form on the surface . Small round or heart-shaped prothallia will then form. Begin to mist lightly with distilled water weekly until true fronds develop. Transplant sporelings when large enough to handle. Good ferns can usually be had in 8 - 12 months from spores.

SOIL MIXES

Many seeds do well sown direct to ordinary garden soil, but even good soil may be poor in pots or flats. These need a lighter, looser soil. Most commercial mixes are fine, but the addition of some garden soil and compost will often insure adequate beneficial micro-organisms & fungi, A good soil mix can be made at home from 1/3 garden loam, 1/3 peat or compost, and 1/3 gritty sand. Number 1 limestone chick-grit makes a good top dressing for many alpines or slow germinating seed to discourage algae growth. Crushed charcoal also helps.

HARD SHELLED SEED

These have hard impermeable shells and need nicking or scratching the coat to allow water to enter and the seed to germinate. The best results are from the least amount of nicking that will allow water to enter and the seed to swell. Many failures are due to over-nicking and damaging the seed.
Different seeds need varying amounts of nicking. Most do best with lightly rubbing on sandpaper or a file until just the very outer coat is scratched. Often just scratching with a knife-point or scriber works. Others need serious nicking, Then soak the seed overnight .
OTHER METHODS for large lots include:
Hot Water Soak: The seeds are placed in a cup and not quite boiling (200°F) water is poured on them and allowed to cool & the seeds to swell. At least 4 - 5 times their volume of water is used.

COLD TREATMENT (Prechill)

Many seeds need a cold moist period before they will sprout. The essentials are moisture, air, cold and time.
1. Soak seed overnight until swollen or soft (up to four days for large hard nuts). Nick if needed.
2. Mix seed with about 3 times its volume of damp peat moss or vermiculite and place in a plastic bag or pill bottle. Small amounts may be conveniently layered between damp paper towels or coffee filters. Remember, air is essential; avoid sogginess. Label the bag with the name of the seed and date to be removed from cold.
3. Store in the refrigerator (34 - 40°F) for the time specified . Four to 12 weeks is usual.
4. Remove the seed and sow. Seed is best kept cool (50°F or so) for a week after sowing, and gradually brought up to warm temperatures. Warming too quickly can be fatal for some seeds.
'Cold germinators' only sprout at cold temperatures, and are most conveniently treated by layering in damp towels and pricked off as they germinate.
If using outdoor treatment, hold pots at above freezing for a few weeks before putting outside.