Seed Germination Reference Days, temps, and what to expect

Find any seed's germination profile

Search by name or browse categories to see days to sprout, soil temperature, light needs, and stratification info for 100+ common garden seeds.

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Seeds that need light to germinate

Press these on the soil surface. Do not bury them.

  • Lettuce
  • Dill
  • Petunia
  • Snapdragon
  • Impatiens
  • Celery
  • Columbine

Seeds that need cold stratification

These require weeks of cold, moist conditions before they'll sprout.

  • Lavender (4-6 weeks)
  • Milkweed (30-60 days)
  • Echinacea (30 days)
  • Oak / Acorn (30-90 days)
  • Maple (30-90 days)
  • Dogwood (90-120 days)

Fastest germinators (under 7 days)

Great for impatient gardeners and kids' projects.

  • Radish (3-7 days)
  • Lettuce (2-7 days)
  • Beans (5-7 days)
  • Zinnia (5-7 days)
  • Cosmos (5-7 days)
  • Sunflower (5-7 days)

When nothing sprouts: troubleshooting

1

Check the soil temperature

This is the number one cause of slow or failed germination. A $15 soil thermometer tells you more than guessing. If your soil is below the minimum on the chart, wait or add a heat mat.

2

Check moisture level

Soil should feel like a wrung-out sponge. Too dry and the seed never activates. Too wet and it rots. Cover trays with plastic wrap or a humidity dome to hold moisture until sprouts appear.

3

Check planting depth

A common mistake: planting too deep. Most seeds need to be buried 1-2x their thickness. Tiny seeds like lettuce and petunia should sit on the surface with just a light dusting of soil.

4

Check seed age

Old seeds lose viability. Tomato and pepper seeds last 3-5 years if stored cool and dry. Parsnip and onion seeds are best used within one year. If your seeds are 3+ years old, buy fresh.

5

Did you forget stratification?

If the chart says the seed needs cold treatment and you skipped it, that's likely the problem. Put seeds in damp sand in a sealed bag in the fridge for the listed number of weeks, then plant.

6

Wait 1.5x the max days

Some seeds just take longer than the packet says, especially in cool soil. Only give up after 1.5 times the maximum listed days. At that point, start a fresh batch.

How to read this reference

Understanding day ranges

Every entry shows a range like '7-14 days.' The low end assumes ideal temperature and moisture. The high end is what you might see in average conditions. Cool soil adds days. A heat mat at the right temperature subtracts them.

Soil temperature vs air temperature

All temperatures here are soil temperature, not air. Soil runs 5-10°F cooler than air in spring. A warm sunny day doesn't mean your seed tray is warm. Use a soil thermometer or set your heat mat to the target temperature.

What 'needs light' really means

Light-dependent seeds have a hormone that only activates when they sense light. If you bury them in dark soil, they sit there doing nothing. Press them on the surface, mist gently, and keep them under a grow light or bright window.

Stratification shortcuts

For tree seeds with hard coats like oak or maple, you can also scarify (nick the seed coat with a file or knife) before cold treatment. This speeds up water absorption and can cut stratification time by a few weeks.

Data compiled from Johnny's Selected Seeds, Burpee, Botanical Interests, and university extension services. Last updated: January 2026.