Transplant seedlings when they have 2-4 true leaves (not the initial seed leaves), roots are visible at drainage holes, and weather conditions are appropriate for the plant type. For most vegetables, this means soil temperatures above 50°F (10°C) for cool-season crops and 60°F (15°C) for warm-season crops like tomatoes and peppers.
Signs Seedlings Are Ready to Transplant
Must-Have Signs
| Sign | What It Means |
|---|---|
| True leaves present | 2-4 sets beyond seed leaves |
| Root development | Visible at drainage holes |
| Sturdy stem | Can support its own weight |
| Healthy color | Not yellowing or pale |
It's Time to Pot Up When...
- Roots are circling the bottom
- Growth has slowed
- Needs watering more than daily
- Plant is top-heavy
It's Time to Move Outdoors When...
- Hardening off is complete (7-10 days)
- Weather matches plant needs
- Frost risk has passed (for warm crops)
- Soil temperature is appropriate
Transplant Timing by Crop Type
Cool-Season Vegetables
| Crop | Transplant Size | Weeks Before Last Frost | Soil Temp |
|---|---|---|---|
| Broccoli | 4-6 leaves | 2-4 weeks before | 40°F+ |
| Cabbage | 4-6 leaves | 2-4 weeks before | 40°F+ |
| Lettuce | 4-6 leaves | 3-4 weeks before | 35°F+ |
| Kale | 4-5 leaves | 4-6 weeks before | 40°F+ |
| Onions | Pencil thickness | 4-6 weeks before | 40°F+ |
Warm-Season Vegetables
| Crop | Transplant Size | After Last Frost | Soil Temp |
|---|---|---|---|
| Tomatoes | 6-8" tall, sturdy | 1-2 weeks after | 60°F+ |
| Peppers | 4-6" tall | 2 weeks after | 65°F+ |
| Eggplant | 4-6" tall | 2-3 weeks after | 65°F+ |
| Cucumber | 2-3 true leaves | 1-2 weeks after | 60°F+ |
| Squash | 2-3 true leaves | 1-2 weeks after | 60°F+ |
Herbs
| Herb | Transplant Size | Timing | Notes |
|---|---|---|---|
| Basil | 3-4 true leaves | After last frost | Cold-sensitive |
| Parsley | 3-4 true leaves | 2-4 weeks before | Tolerates cool |
| Cilantro | 2-3" tall | Early spring/fall | Bolts in heat |
| Thyme | 2-3" tall | Spring | Hardy once established |
| Oregano | 2-3" tall | After frost | Tolerates some cold |
Flowers
| Flower | Transplant Size | Timing | Notes |
|---|---|---|---|
| Marigolds | 3-4 true leaves | After last frost | Easy to transplant |
| Zinnias | 3-4 true leaves | After last frost | Direct sow preferred |
| Petunias | 3-4 true leaves | After frost | Harden well |
| Snapdragons | 4-6 true leaves | 2-4 weeks before | Cool-tolerant |
| Cosmos | 3-4 true leaves | After frost | Direct sow preferred |
Indoor Pot-Up Timing
When to move seedlings to larger containers indoors:
Signs to Pot Up
- Root bound — Roots visible at holes, circling
- Growth stalled — Was growing, now stopped
- Frequent watering — Drying out daily
- Top heavy — Plant tips over
- Time — 3-4 weeks in small cells
Pot-Up Schedule
| Starting Size | Move To | Typical Time |
|---|---|---|
| Cell tray (1-2") | 3-4" pot | 2-3 weeks |
| 3-4" pot | 4-6" pot | 3-4 weeks |
| 4-6" pot | Outdoor/final | When conditions right |
Extending Time Without Pot-Up
If weather isn't ready but seedlings are:
- Pot extensions — Add vertical space without transplanting
- Liquid fertilizer — Keep nutrition up in exhausted soil
- Pruning — Pinch to slow growth (tomatoes)
- Cooler temps — Slow growth indoors
Transplanting Too Early vs. Too Late
Too Early
Risks:- Cold damage or death
- Stunted growth
- Extended establishment time
- Pest vulnerability
- Purple leaves (cold stress)
- No growth for weeks
- Yellowing
- Wilting despite moisture
Too Late
Risks:- Root-bound plants
- Transplant shock (larger = harder)
- Delayed production
- Heat stress during establishment
- Severely root-bound
- Flowering before transplant
- Leggy, weak stems
- Poor establishment
How to Calculate Transplant Dates
Working Backwards Method
- Find your last frost date
- Look up crop timing (table above)
- Count backwards for seed starting
- Count forward for transplanting
| Crop | Transplant After | Transplant Date |
|---|---|---|
| Tomatoes | 2 weeks after | May 29 |
| Peppers | 2 weeks after | May 29 |
| Broccoli | 4 weeks before | April 17 |
| Lettuce | 3 weeks before | April 24 |
Using Soil Temperature
More accurate than calendar dates:
| Soil Temp | Safe for |
|---|---|
| 40°F (4°C) | Lettuce, kale, spinach, onions |
| 50°F (10°C) | Broccoli, cabbage, carrots |
| 60°F (15°C) | Tomatoes, corn, beans |
| 65°F (18°C) | Peppers, eggplant, cucumbers |
| 70°F (21°C) | Melons, sweet potatoes |
FAQ
How do you know when seedlings are ready to transplant?
Look for 2-4 true leaves (not seed leaves), roots visible at drainage holes, and a sturdy stem. The plant should be healthy and actively growing.
What happens if you transplant seedlings too early?
Cold stress can stunt or kill plants. Even if they survive, growth may stall for weeks. Wait until soil temperatures match plant requirements.
How big should seedlings be before transplanting outdoors?
It varies by crop. Tomatoes should be 6-8" with sturdy stems. Lettuce needs 4-6 true leaves. Cucurbits are ready with just 2-3 true leaves (they hate root disturbance, so transplant early).
Should I transplant on a cloudy day?
Yes, ideal conditions are cloudy, cool, or evening. This reduces transplant shock by lowering stress on the plant while roots establish.
What if my seedlings are ready but the weather isn't?
Options: pot up to larger containers, use pot extensions, slow growth with cooler temperatures, or use protection outdoors (row cover, cold frame).
How long after transplanting until plants grow?
Most plants show new growth within 1-2 weeks. Some wilting or stalling in the first week is normal. If no growth after 3 weeks, something may be wrong.
The Bottom Line
Transplant timing depends on:
- Plant readiness — True leaves, root development
- Weather conditions — Soil temp, frost risk
- Hardening off — 7-10 days of gradual exposure
When in doubt, wait a few more days. A slightly larger, hardened-off seedling handles transplanting better than a rushed one.
Related: How to Prevent Transplant Shock | What Size Pot for Tomato Seedlings