Saving vegetable seeds: open-pollinated vs F1, wet vs dry, germination tests

You can save vegetable seed to sow yourself if you pick open-pollinated varieties and start with crops that pollinate within their own flowers. Seed from an F1 hybrid grows into plants that don’t match the parent. This lesson covers which plants to save from, how wet and dry seeds are handled, how to dry and store seed so it lasts in a hot, humid climate like Thailand’s, and how to test germination and work out how many seeds to sow.

Open-pollinated vs F1 hybrid

	Open-pollinated	F1 hybrid
How it is made	pollinated within the same variety for generations	a cross between two inbred parent lines
Saving seed	next generation looks and yields much like the parent	next generation varies, doesn’t match the parent, and usually underperforms
Strength	you can save your own seed every year	vigorous, uniform plants
On the packet	no “F1”	says F1 or hybrid

Heirloom varieties handed down over the years are a kind of open-pollinated variety. One thing to know: older varieties often have weaker disease resistance than modern ones.

Self-pollinating vs cross-pollinating crops

Self-pollinating crops pollinate within a single flower and rarely cross with other plants, so their seed easily comes true. They are the place to start: tomatoes, beans, peas, peppers and lettuce.

Cross-pollinating crops rely on wind or insects to carry pollen from other plants: squash and the rest of the cucumber and melon family, corn, cabbage and its relatives, carrots and beets. If you grow several varieties near each other, the seed will be an unpredictable cross. To avoid that, grow only one variety of that species in a season, separate varieties by distance, cover plants with netting, or stagger planting so they flower at different times.

Save from healthy, disease-free plants, and from many plants. A University of Georgia guide recommends at least 20 plants for self-pollinated crops and 80 for cross-pollinated crops to keep the variety’s diversity. A home garden rarely reaches those numbers, which is one more reason to start with self-pollinators.

Wet seeds and dry seeds

	Wet seed	Dry seed
Examples	tomato, cucumber, eggplant, watermelon	beans, peas, peppers, basil and herbs saved from flowers
When to harvest	fully ripe fruit	pods dry and brown until the seeds rattle; peppers left to ripen until the skin starts to wrinkle
Processing	ferment to remove the gel around the seed, then rinse	shell from pods or flowers and remove the chaff

Fermenting tomato seed, step by step

1. Scoop the seeds and gel into a container. If it is too thick to stir, add a little water.
2. Keep it at about 22-30°C (72-86°F) and stir 2-3 times a day.
3. Ferment for 48-72 hours. A thin layer of white mould on top is harmless and shows fermentation is working.
4. It is done when the gel around the seeds is gone. Good seeds sink; pour off the liquid, pulp and floating seeds.
5. Rinse in a strainer until the water runs clear, then dry.

If seeds start to sprout during fermentation, they have soaked too long.

Drying them properly

Spread seeds in a single layer on a plastic, glass or ceramic plate. Avoid paper towels and wax paper, because seeds stick to them. Put them somewhere dry and airy; the UGA guide suggests 20-40% relative humidity, such as an air-conditioned room, and drying takes 2 weeks or more.

For beans and peas, let the pods dry on the plant, then dry them indoors for at least 2 more weeks before shelling, or simply keep them in the pod until planting. Label every plate, especially if you are saving several varieties of the same crop.

Storing seed in a hot, humid climate

Heat and moisture are what kill seed. A rule of thumb from the UGA guide: temperature (°F) + relative humidity (%) should be no more than 100.

Try it for a Thai home:

1. On a shelf at 30°C = 86°F, humidity would need to be at most 100 - 86 = 14%. A normal room can’t do that.
2. In the main compartment of a fridge at about 5°C = 41°F, humidity needs to be at most 100 - 41 = 59%. A sealed glass jar with silica gel can manage that.

So in Thailand the fridge is the best place. Use a glass jar with a rubber seal, with the seed in paper envelopes labelled with the variety and date. Plastic is not a good moisture barrier. When you take the jar out, let it warm to room temperature before opening, or moisture will condense on the seed. Large seeds such as beans can go in the freezer, which also helps against insects.

Seed life under dry, cold storage, from the UGA guide: onion 2 years, beans and peppers 3, tomato and eggplant 4-5, cucumber, lettuce and spinach 5.

Seed that isn’t fully dry will go mouldy in a sealed jar. Always dry it completely before storing.

Testing germination and working out how many to sow

1. Lay 25 seeds on a damp paper towel and roll it up.
2. Put the roll in a zip-top bag with a few small pinholes, somewhere consistently at least 24°C (75°F). Most Thai homes manage that easily.
3. Unroll and count the sprouted seeds on day 7 and day 14.
4. Germination rate = total sprouted ÷ 25.

Example. You saved pepper seed last year, and 18 of the 25 test seeds sprout.

• Germination rate = 18 ÷ 25 = 0.72, or 72%.
• To get 20 seedlings, sow 20 ÷ 0.72 ≈ 27.8, rounded up to 28 seeds.
• If only 10 sprouted (40%), you would need 20 ÷ 0.40 = 50 seeds. At that point, it is time to save a fresh batch.

For comparison, UGA lists U.S. minimum germination standards for seed sold commercially, such as tomato 75%, lettuce and cucumber 80%, pepper 55%. Home-saved seed near those numbers is doing fine.

Common mistakes

• Saving seed from an F1 fruit. The plants come out different and usually yield less.
• Saving squash seed from several varieties grown side by side. You get an unpredictable cross.
• Saving from only one plant, or only the latest ones. The variety narrows, and saving only from late plants slowly selects for late fruiting.
• Drying on paper towels. The seeds stick and won’t come off.
• Storing at room temperature or in plastic bags. Too hot and too humid; seed life drops sharply.
• No labels. Next year you won’t remember which jar is which.

Sources

• Variety Selection and Seed Saving for Organic Growers (B1486) — UGA Cooperative Extension
• Seed Saving Basics — UGA Extension Camden County
• Which plants are easiest to save seed from? — Iowa State University Extension