Test your saved or stored seeds, find out if germination rate is acceptable, and calculate exactly how many seeds to plant to hit your target stand count.
A germination test tells you whether stored or saved seeds are still worth planting before you commit an entire bed to them. The paper towel method is the simplest approach and works for almost every vegetable seed. Dampen a paper towel until it is moist but not dripping. Count out 10 or 20 seeds — 10 is enough for most home gardeners, 20 gives a more accurate rate — and space them evenly across one half of the towel. Fold the other half over the seeds, then slide the towel into a zip-lock bag or sealed container. Label it with the seed variety and date. Place the bag somewhere consistently warm: the top of a refrigerator, a high shelf in a heated room, or near a water heater. Most vegetable seeds germinate fastest between 65–80°F.
Check daily for sprouting. Count a seed as germinated when the radicle (the white root tip) has visibly emerged — it does not need to be a full seedling. Tally your results at the expected germination window for that crop (see the reference table below). Divide sprouted seeds by total seeds tested and multiply by 100 for your germination rate percentage. A rate above 80% means your seeds are excellent and you can plant at normal spacing. A rate of 60–80% is still usable — plant 25–35% more seeds and thin to your target spacing. Below 40%, seriously consider buying fresh seed rather than overplanting and hoping for the best.
Seeds lose viability at different rates depending on the species and storage conditions. Onions, parsnips, and leeks are notoriously short-lived — most are nearly worthless after 1–2 years even under good storage. Carrots and peppers typically last 3–4 years. Tomatoes, squash, and brassicas store well for 4–5 years in cool, dry conditions. Beans and corn can push 5–6 years. Cucumbers and melons often exceed 6 years with proper storage. These ranges assume seeds are kept in airtight containers at 40–50°F with low humidity. A sealed mason jar in the back of a refrigerator is nearly ideal. Heat and moisture are the enemies of viability — a garage or greenhouse in summer will cut expected lifespan by half or more.
Seed saving from open-pollinated or heirloom varieties follows the same storage rules. Seeds saved from hybrid (F1) varieties will not breed true to the parent plant and are not worth saving for replanting. If you are uncertain whether your saved seed is open-pollinated or hybrid, run a germination test and also observe the seedling closely — hybrid offspring are often visually inconsistent.
| Crop | Optimal Soil Temp (°F) | Days to Germination | Min Viable Rate |
|---|---|---|---|
| Tomato | 70–80°F | 5–10 days | 75% |
| Pepper | 75–85°F | 7–14 days | 65% |
| Lettuce | 45–65°F | 2–8 days | 70% |
| Squash / Zucchini | 70–90°F | 5–10 days | 75% |
| Bean | 65–85°F | 5–10 days | 70% |
| Corn | 60–95°F | 4–8 days | 75% |
| Carrot | 55–75°F | 10–21 days | 55% |
| Onion | 50–75°F | 7–14 days | 60% |
| Brassica (Cabbage / Broccoli / Kale) | 45–85°F | 3–10 days | 70% |
Seed saving is one of the most rewarding skills on a homestead, but there is a practical break-even point where overplanting old seed costs more in time, bed space, and frustration than simply ordering fresh. If your germination rate is below 40%, the math rarely works out. To hit a stand of 20 plants at a 35% germination rate, you would need to sow roughly 63 seeds — more than three times the normal seeding rate. For a crop like pepper where each plant represents weeks of growing time and space in the garden, that's a significant gamble. A $3–5 packet of fresh seed with an 85% germination rate will outperform overplanting old seed almost every time.
Ten seeds is the practical minimum for home gardeners — it gives you a germination rate in 10% increments (1 seed = 10%, 2 seeds = 20%, etc.) and wastes few seeds. If you have plenty of seed and want a more precise result, test 20 seeds. Commercial seed labs use 50–100 seeds for statistically valid data, but that level of precision is rarely needed for a garden planting decision. The key is being consistent: keep the towel at a stable temperature, check daily, and tally at the right number of days for your crop type.
Only count seeds where the radicle (root tip) has clearly emerged from the seed coat. A cracked seed coat with no root showing does not count as germinated. Seeds that are mushy or rotted should be noted separately — a high rate of rotting alongside low germination often indicates the seeds were stored at too-high humidity and suffered mold damage, not just age-related decline. If you see a lot of rot, inspect your storage conditions before assuming the seed lot is simply old.
For most vegetables, soaking is not necessary for a paper towel test and is not recommended — it can waterlog the seeds and cause rot rather than germination. Large-seeded crops like beans, corn, and squash can benefit from a 4–8 hour presoak in room-temperature water before direct sowing in the garden, but for a germination test the moist towel provides all the moisture needed. The exception is parsley, which has natural germination inhibitors that a 24-hour soak can help break down.
You can plant them, but understand what you're accepting. If 3 out of 10 seeds germinated in a controlled test on a warm paper towel, you should expect equal or worse results in the garden where soil temperature fluctuates, insects may eat seeds, and moisture is less consistent. The germination rate you measured is the ceiling, not a floor. If you decide to proceed with poor-viability seed, sow at least two to three times your target stand and plan to thin aggressively — or accept a gappy, uneven planting.