When to Start Fertilizing Seedlings
Don’t fertilize seedlings until they have 2-3 sets of true leaves. Then use 1/4 strength liquid fertilizer every 2 weeks.
Seed-starting mix has no nutrients. Once the seed’s stored energy runs out, the plant needs food.
The Timeline
| Stage | Fertilize? |
|---|---|
| Germination | No |
| Cotyledons (first leaves) | No |
| 1-2 sets true leaves | No |
| 2-3 sets true leaves | Yes, 1/4 strength |
| Vegetative growth | Every 2 weeks |
| Flowering/fruiting | Every 1-2 weeks |
How Much
Liquid fertilizer:
- Seedlings: 1/4 label recommendation
- Established: 1/2 to full
- Every 2 weeks
Rule: When in doubt, use less.
Signs You Fertilized Too Early
- Brown, crispy leaf edges
- White crust on soil
- Wilting despite wet soil
- Yellowing leaves
Fix: Flush soil with water. Skip fertilizer 2 weeks.
Signs You Waited Too Long
- Slow growth
- Pale leaves
- Old leaves yellow first
- Stunted plants
Fix: Fertilize at 1/4 strength.
Common Questions
Can I fertilize seeds? No. Seeds don’t need it.
What about potting soil? It has fertilizer. Don’t fertilize for 4-6 weeks.
Is organic better for seedlings? Not necessarily. Both work.
How often should I fertilize tomatoes? Every 1-2 weeks once flowering.
Should I fertilize in winter? No. Plants are dormant.
Can I over-fertilize? Yes. It’s the most common beginner mistake.