When and how to fertilize seedlings
NDSU says wait until several sets of true leaves have appeared. Oklahoma State says a quarter strength dose within 5 days of germination.
What the sources say
| Source | When to start | Strength |
|---|---|---|
| NDSU Extension | After several sets of true leaves have appeared. Until then, seedlings use food stored in their seed leaves. | Water-soluble fertiliser at quarter or half strength for the first couple of applications, then full strength |
| Oklahoma State Extension | Within 5 days of germination | Quarter strength; liquid fertiliser is generally the best choice |
Choosing
- Both sources agree on diluted, liquid fertiliser at first.
- If your seed starting mix has starter fertiliser, UConn says it runs out and plants then need regular feeding. See seed starting mix.
- Utah State lists reducing fertiliser as part of the fix for leggy seedlings. See leggy seedlings. More feed does not make up for weak light.
Sources
- NDSU Extension, Dakota Gardener: Watering and waiting
- Oklahoma State University Extension: Tips for starting seeds at home (2025)
- UConn Home & Garden Education Center: Potting media (PDF)
- Utah State University Extension: Starting vegetable seeds indoors, seeding culture and transplanting (2025)