How to Fertilize Tomatoes
Tomatoes are heavy feeders - give them the nutrients they need for abundant fruit
Quick Reference
Fertilizing by Growth Stage
At Planting
Mix compost and a balanced slow-release fertilizer into the planting hole. Add a handful of bone meal for phosphorus. Don't overdo nitrogen - it encourages leaves over fruit.
Early Growth (Before Flowering)
Feed every 3-4 weeks with balanced fertilizer (10-10-10). Plants need nitrogen for strong vegetative growth at this stage, but don't overdo it.
Flowering & FruitingCritical
Switch to low-nitrogen, high-phosphorus fertilizer (5-10-10 or similar). Feed every 2-3 weeks. Too much nitrogen now causes lots of leaves but few tomatoes.
Late Season
Reduce or stop fertilizing 4-6 weeks before your expected first frost. Let plants focus on ripening existing fruit rather than producing new growth.
Best Fertilizers for Tomatoes
Organic Options
- • Compost - Balanced nutrition, improves soil
- • Fish emulsion - Quick nitrogen boost
- • Bone meal - Phosphorus for fruiting
- • Kelp meal - Micronutrients, potassium
- • Worm castings - Gentle, balanced
Synthetic Options
- • Tomato-specific fertilizers - Formulated for tomatoes
- • 10-10-10 - Balanced, for early growth
- • 5-10-10 - For flowering/fruiting
- • Slow-release granular - Convenient, steady
- • Water-soluble - Fast-acting, for containers
Common Tomato Fertilizing Mistakes
- • Too much nitrogen - Beautiful plants with no tomatoes
- • Fertilizing dry soil - Burns roots; always water first
- • Ignoring calcium - Leads to blossom end rot
- • Over-fertilizing - More isn't better; follow directions
- • Same fertilizer all season - Needs change as plant grows
Container Tomato Fertilizing
Container tomatoes need more frequent fertilizing because nutrients wash out with watering.
- • Use slow-release fertilizer in potting mix at planting
- • Supplement with liquid fertilizer weekly at half strength
- • Or use full-strength liquid fertilizer every 2 weeks
- • Watch for yellowing leaves - a sign of nutrient depletion
- • Consider self-watering containers to reduce nutrient leaching
Frequently Asked Questions
How often should I fertilize tomatoes?
Fertilize tomatoes every 2-3 weeks once they start flowering. Before flowering, feed every 3-4 weeks. Container tomatoes may need weekly feeding with diluted fertilizer.
What's the best fertilizer for tomatoes?
Use a balanced fertilizer (like 10-10-10) early on, then switch to a low-nitrogen, high-phosphorus fertilizer (like 5-10-10) once plants start flowering to encourage fruit production.
Can you over-fertilize tomatoes?
Yes! Over-fertilizing causes excessive leafy growth with few fruits, blossom end rot, and can burn roots. More fertilizer doesn't mean more tomatoes.
Should I fertilize tomatoes when planting?
Mix compost or slow-release fertilizer into the planting hole. Avoid high-nitrogen fertilizers at planting - they encourage leaves over roots and fruit.