Seed-starting field guide
Quick answer: When seeds do not sprout, check the seed's expected germination window first. Then inspect moisture, temperature, planting depth or light needs, seed age and storage, special dormancy requirements, drainage, and signs of rot or damping-off. Change one variable at a time.
First ask whether the seed is actually late
Different species germinate on different schedules, and even one species can slow under cool or inconsistent conditions. Check the variety's expected germination range before disturbing the soil. Repeated digging can damage a seed that is still alive.
Keep a sowing record
Write down the variety, lot or year, sowing date, depth, medium, temperature range, and any pretreatment. Without those details, troubleshooting becomes guesswork.
If the normal window has passed, inspect a small sample rather than the whole tray or row. A swollen, firm seed suggests a different problem than a dry, unchanged seed or a soft, rotted one.
Check the seven most common causes in order
| Check | What can go wrong | Useful response |
|---|---|---|
| Moisture | Drying interrupts imbibition; saturation reduces oxygen and promotes rot. | Keep the medium evenly moist, not waterlogged. |
| Temperature | Conditions are outside the crop's useful range. | Measure the medium, not just room air, and follow crop-specific guidance. |
| Depth and light | Seed is buried too deeply, exposed, or denied a light requirement. | Match sowing depth to seed size and species instructions. |
| Seed condition | Age, heat, humidity, or poor storage reduced viability. | Run a small germination test and replace weak lots when needed. |
| Dormancy | The species needs cold stratification, scarification, or another preparation. | Follow species-specific pretreatment rather than applying one method to all seed. |
| Oxygen and drainage | Compacted or saturated media limits oxygen. | Use a porous seed-starting mix and containers with drainage. |
| Disease or pests | Seed rots, seedlings collapse, or seed is eaten or washed away. | Inspect closely, improve sanitation, and correct the source condition. |
Moisture and temperature must work together
A seed needs water to begin germination, but roots and embryos also need oxygen. A constantly saturated tray can fail even though it never looks dry. Fine seed-starting media should drain while holding enough moisture for the germination period.
Temperature needs are crop-specific. Cool-season vegetables and warm-season vegetables should not be forced into one setting. A heat mat may help selected warm-requiring crops, but it can be unnecessary or too warm for others. Remove or adjust heat after emergence when the seedlings' needs change.
Browse seed-starting supplies, but remember that equipment cannot correct an unsuitable temperature target or saturated medium.
Respect sowing depth, light response, and dormancy
Large seeds generally have more stored energy to emerge from depth than dust-like seeds. Very small seed can disappear under too much medium. Some species germinate better with light exposure, while others need darkness. Follow the species or packet instructions instead of using one depth for every tray.
Native flowers and perennials may have dormancy mechanisms that prevent immediate germination. Cold-moist stratification, scarification, warm-cold cycles, or time may be required. Do not assume a dormant seed is dead, and do not apply cold stratification to crops that do not need it.
Germination is not a race. The goal is to provide the conditions that the species recognizes.
Separate germination failure from damping-off
Sometimes seed germinates and the seedling dies so quickly that the tray looks like a germination failure. Damping-off can rot seed before emergence or constrict young stems near the soil line after emergence. Crowding, contaminated containers, excessive moisture, poor airflow, and cool wet conditions can increase risk.
Reduce damping-off risk
- Use clean containers and a fresh, well-drained medium.
- Avoid overwatering and standing water.
- Provide appropriate warmth for germination, then adequate light and airflow after emergence.
- Thin crowded seedlings and remove collapsed plants.
- Do not reuse a diseased medium for another sowing.
Run a small test before discarding a seed lot
Place a counted sample in an appropriate moist test setup, keep it at a suitable temperature, and record how many germinate within the expected period. A test does not guarantee field performance, but it helps distinguish a weak seed lot from a problem in the tray or garden.
If germination is low but usable, sowing more heavily may compensate for a small personal planting. For important or scarce seed, avoid consuming the whole lot in repeated uncontrolled attempts. Change one suspected variable, label the test, and compare the result.
For outdoor crop planning, pair this guide with the Mid-Atlantic garden seed planting guide.
Frequently asked questions
Why did none of my seeds germinate?
A complete failure often points to a shared condition such as temperature, moisture, planting depth, old seed, or a medium problem. Check the records and inspect a small sample.
Can soil be too wet for germination?
Yes. Seed needs moisture, but saturated conditions can reduce oxygen and promote rot.
Should I use a heat mat for every seed?
No. Temperature needs vary by crop. Use a heat mat only when it helps reach an appropriate medium temperature, and monitor it.
How do I know whether seed is dead or dormant?
Review species-specific dormancy requirements and run a controlled test. Some native or perennial seed may need preparation or a long cycle before emergence.
Why did seedlings emerge and then fall over?
That pattern can indicate damping-off or another stem and root problem. Check moisture, sanitation, crowding, airflow, and the stem at the soil line.
Garden timing changes with weather, elevation, soil, seed lot, and local conditions. Use this guide as a planning framework and confirm local windows with your Cooperative Extension service.
