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Gardening glossary

Germination

Germination is the moment a seed transitions from a dry, storage-stable package into an actively growing plant. The trigger is water — when a dry seed absorbs moisture (imbibition), enzymes inside the embryo activate, stored starch and oils convert into sugars, and the radicle (embryonic root) emerges through the seed coat.

The four conditions every seed needs:

1. **Water.** Enough to fully imbibe the seed and rehydrate the embryo, but not so much that the seed sits in standing water and suffocates. 2. **Oxygen.** Germinating seeds respire heavily. Water-logged soil shuts germination down. 3. **Temperature.** Each species has an optimum range. Lettuce germinates best at 15–20 °C and stalls above 25 °C. Tomatoes prefer 20–30 °C. Peppers want 25–32 °C and may take 14+ days at cooler temperatures. 4. **For some seeds, light or darkness.** Lettuce, celery, and many alpine seeds need light to germinate (surface-sow them). Pansies, phlox, and verbena prefer darkness (cover with vermiculite). Most vegetable seeds are indifferent.

Some seeds add a fifth requirement: a pre-treatment that simulates winter or weathering. [Cold stratification](/glossary/stratification) breaks dormancy in many tree, shrub, and perennial seeds. Scarification (nicking the seed coat with a file or sandpaper) helps hard-coated seeds like morning glory, lupin, and sweet pea.

Common germination problems and fixes:

- **Old seed.** Most vegetable seed loses 10–20% viability per year after the first; do a paper-towel viability test on packets more than three years old. - **Too cold.** Use a heat mat to bring soil temperature into the species' sweet spot — often the single highest-leverage fix. - **Drying out.** Cover trays with a humidity dome or cling film until the first sprouts appear, then remove immediately. - **Damping off.** Once seedlings emerge, ventilate well, water from below, and avoid overwatering — see our [damping-off entry](/glossary/damping-off) for the full prevention checklist.

The Growli app schedules sowing windows and tracks germination expectations per species so you know whether your seed is slow or actually dead.

Where this comes up in our guides

Related terms

Stratification

Stratification is a seed pre-treatment that simulates the conditions a seed would experience naturally before germinating in spring. Cold-moist stratification (4 to 8 weeks at 1 to 4 °C) breaks dormancy in most temperate perennial, tree, and shrub seeds.

Dormancy

Dormancy is a plant's built-in rest period — triggered by short days, cold, or drought — when growth slows or stops and metabolism drops. Recognizing dormancy is the difference between a healthy winter pause and a "dying" plant you accidentally drown.

Photoperiod

Photoperiod is a plant's response to the relative length of day and night. Short-day plants flower when nights exceed a critical length; long-day plants flower when nights are short; day-neutral plants flower based on age and temperature instead.

Damping off

Damping off is a soil-borne fungal disease that kills seedlings within days of germination, caused by Pythium, Rhizoctonia, Fusarium, and Phytophthora species. Seedlings collapse at the soil line with a pinched, water-soaked stem. Prevention is the only real cure — by the time you see symptoms, intervention is usually too late.