When to Start Seeds Indoors: Zone-by-Zone Guide
Quick Answer
Count backwards from your last frost date. Most vegetables need 6-8 weeks indoors before transplanting. Tomatoes and peppers: start 6-8 weeks before last frost. Cucumbers and squash: 3-4 weeks. Lettuce: 4-6 weeks. Check your zone below for specific dates.
Want exact dates for your garden? Get a free personalized planting calendar →
How to Calculate Your Seed Starting Date
- Find your USDA hardiness zone
- Look up your average last frost date
- Count backwards based on the crop
Formula: Last Frost Date - Weeks Indoors = Seed Starting Date
Seed Starting Dates by Zone
Zone 3 (Last Frost: May 15-30)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | March 15-April 1 |
| Peppers | 8-10 weeks | March 1-15 |
| Broccoli | 6-8 weeks | March 15-April 1 |
| Lettuce | 4-6 weeks | April 1-15 |
| Cucumbers | 3-4 weeks | April 15-May 1 |
Zone 4 (Last Frost: May 1-15)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | March 1-15 |
| Peppers | 8-10 weeks | Feb 15-March 1 |
| Broccoli | 6-8 weeks | March 1-15 |
| Lettuce | 4-6 weeks | March 15-April 1 |
| Cucumbers | 3-4 weeks | April 1-15 |
Zone 5 (Last Frost: April 15-30)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | Feb 15-March 1 |
| Peppers | 8-10 weeks | Feb 1-15 |
| Broccoli | 6-8 weeks | Feb 15-March 1 |
| Lettuce | 4-6 weeks | March 1-15 |
| Cucumbers | 3-4 weeks | March 15-April 1 |
Zone 6 (Last Frost: April 1-15)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | Feb 1-15 |
| Peppers | 8-10 weeks | Jan 15-Feb 1 |
| Broccoli | 6-8 weeks | Feb 1-15 |
| Lettuce | 4-6 weeks | Feb 15-March 1 |
| Cucumbers | 3-4 weeks | March 1-15 |
Zone 7 (Last Frost: March 15-April 1)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | Jan 15-Feb 1 |
| Peppers | 8-10 weeks | Jan 1-15 |
| Broccoli | 6-8 weeks | Jan 15-Feb 1 |
| Lettuce | 4-6 weeks | Feb 1-15 |
| Cucumbers | 3-4 weeks | Feb 15-March 1 |
Zone 8 (Last Frost: March 1-15)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | Jan 1-15 |
| Peppers | 8-10 weeks | Dec 15-Jan 1 |
| Broccoli | 6-8 weeks | Jan 1-15 |
| Lettuce | 4-6 weeks | Jan 15-Feb 1 |
| Cucumbers | 3-4 weeks | Feb 1-15 |
Zone 9 (Last Frost: Feb 1-15)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | Dec 1-15 |
| Peppers | 8-10 weeks | Nov 15-Dec 1 |
| Broccoli | 6-8 weeks | Dec 1-15 |
| Lettuce | 4-6 weeks | Dec 15-Jan 1 |
| Cucumbers | 3-4 weeks | Jan 1-15 |
Zone 10 (Last Frost: Jan 15-30 or frost-free)
| Crop | Weeks Before Transplant | Start Seeds |
|---|---|---|
| Tomatoes | 6-8 weeks | Nov 15-Dec 1 |
| Peppers | 8-10 weeks | Nov 1-15 |
| Broccoli | 6-8 weeks | Nov 15-Dec 1 |
| Lettuce | 4-6 weeks | Dec 1-15 |
| Cucumbers | 3-4 weeks | Dec 15-Jan 1 |
Complete Seed Starting Timeline
Start 10-12 Weeks Before Last Frost
- Onions
- Leeks
- Celery
Start 8-10 Weeks Before Last Frost
- Peppers (all types)
- Eggplant
Start 6-8 Weeks Before Last Frost
- Tomatoes
- Broccoli
- Cabbage
- Cauliflower
- Kale
Start 4-6 Weeks Before Last Frost
- Lettuce
- Spinach
- Swiss chard
- Basil
Start 3-4 Weeks Before Last Frost
- Cucumbers
- Squash
- Zucchini
- Melons
- Pumpkins
Direct Sow After Last Frost
- Beans
- Corn
- Carrots
- Beets
- Radishes
What You Need to Start Seeds Indoors
Essential supplies:
- Seed starting trays or cell packs
- Seed starting mix (not potting soil)
- Grow lights or sunny south-facing window
- Heat mat (for peppers and tomatoes)
- Spray bottle for watering
Common mistakes:
- Starting too early (leggy, weak seedlings)
- Not enough light (stretching toward window)
- Overwatering (damping off disease)
- Skipping hardening off
Hardening Off: The Critical Step
Before transplanting, seedlings need 7-10 days to adjust to outdoor conditions:
- Day 1-2: 1-2 hours in shade, protected from wind
- Day 3-4: 3-4 hours with some morning sun
- Day 5-6: 5-6 hours with more sun exposure
- Day 7-10: Full days outside, bring in if frost threatens
Skip this step and your seedlings may die from transplant shock.
Get Your Personalized Planting Calendar
Calculating seed starting dates for every crop is tedious. Our AI Garden Planner generates a complete planting calendar based on your zone, including:
- Exact seed starting dates
- Transplant timing
- Direct sow dates
- Harvest windows
Get Your Free Planting Calendar →
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