Seeds and the growing year

1. Harvest fully ripe seed — dry pods, hard kernels, fruit left past eating ripeness. Immature seed stores badly and germinates poorly.
2. Dry it further. Spread thin in shade with moving air for 1–3 weeks. For long storage aim for 5–8% moisture — large seeds like beans should shatter, not dent, when hit with a hammer. Sealing seed in a jar with an equal weight of dried silica gel, or rice dried in an oven, for a week pulls it drier still.
3. Seal it airtight — glass jars with good lids, sealed tins, thick bags inside a tin. Seed sealed damp rots; seed sealed dry lasts.
4. Keep it cool and dark. A cellar, a buried pot, a north-facing store. A refrigerator or freezer extends life enormously for well-dried seed; freezing damp seed kills it.
5. Label everything — crop, variety, year, where it was grown.
6. Protect it from rodents in metal or ceramic, raised off the ground.
7. Split the store. Keep seed in at least two separate places, so one fire, flood or rat plague cannot take all of it. This is the principle of the Svalbard vault, at the scale of a village.

A quick check on the whole store: Harrington's combined rule says storage is good when temperature in °F plus relative humidity in % is below 100 — for example 40 °F (4 °C) at 50% humidity.

Test every store before sowing, every year. It takes two weeks and saves a season.

1. Count out a sample — 100 seeds for a good estimate, 20 or 50 if seed is scarce.
2. Lay them on a damp cloth or paper towel, roll it up loosely, and put it in a covered container or bag so it stays moist but not wet.
3. Keep it warm — 20–25 °C suits most crops.
4. Count the seeds that have sprouted a healthy root after 7–14 days, depending on the crop.
5. Germination rate = sprouted ÷ tested. 85 of 100 is 85%.

Use the number:

• Above ~80% — sow normally.
• 50–80% — sow more thickly, in proportion.
• Below ~50% — sow very thickly, and grow this crop out this season specifically to replace the seed stock, because next year it will be worse.

Save from open-pollinated varieties, not hybrids. Seed from an F1 hybrid — a cross between two parent lines — grows into a mixture of plants unlike the parent, most of them worse. Open-pollinated varieties breed true if they are not crossed with a neighbour.

Keep varieties apart. How far depends on how the crop is pollinated:

Dry-seeded crops — beans, peas, grain, brassicas, lettuce, onions: leave pods and heads on the plant until dry and brittle; if rain threatens, pull whole plants and hang them under cover. Thresh by beating the dry plants on a sheet or treading them, then winnow: pour the mixture from a height in a light breeze, so the chaff blows away and the heavy seed falls.

Wet-seeded crops — tomatoes, cucumbers, melons, squash:

1. Scoop the seeds with their pulp into a jar with a little water.
2. Ferment for 2–4 days at room temperature, stirring daily. A mould film forms; that is expected. Fermentation dissolves the gel that stops seeds germinating and kills some seed-borne diseases.
3. Pour off the floating pulp and the empty seeds that float; the good seed sinks.
4. Rinse and dry thin on a plate or cloth, not paper, which they stick to.

Biennials — carrots, beets, cabbages, onions, parsnips — only flower in their second year. Store the best roots and heads over winter as for eating, replant them in spring, and let them seed.

Planting on time is worth more than almost any other gardening skill, and the two dates that anchor it are local and must be written down:

• The average last spring frost.
• The average first autumn frost.

The days between them are the frost-free season. Crops that cannot survive frost go in after the first and must be harvested before the second. Record frost dates every year — a notched stick, a written log, the date a pond first froze — because a few years of records beat any guess.

Soil temperature decides germination more than air temperature. Seed sown into cold soil sits, rots, or is eaten before it sprouts.