Grow · field guide
Why Your Seedlings Die After Transplant
You grew strong seedlings indoors for 6 to 8 weeks, set them outside, and within days they wilted, turned white, or collapsed. The plants were fine. The problem is transplant shock, from moving soft indoor seedlings straight into harsh sun and wind. Here is how to stop it.
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Harden off over 7 to 14 days
Hardening off means slowly getting seedlings used to the outdoors before they live there full time. Skip it and the sun and wind can undo weeks of work in one afternoon. Take it in steps:
- Days 1 to 2: set them outside 1 to 2 hours in full shade, out of the wind.
- Days 3 to 5: add an hour or two each day, with a little morning sun.
- Days 6 to 10: build up to most of the day in full sun.
- Days 11 to 14: leave them out overnight once lows stay above 50 F, then transplant.
Plant at the right time, the right way
Two more mistakes kill fresh transplants even after a good hardening-off:
- Planting too early. Tomatoes, peppers, and basil die in a late frost. Wait until after your last frost date. The planner gives you the exact date for your ZIP.
- Planting in hot afternoon sun. Set transplants out on a cloudy day or in the evening so the roots settle before the sun hits them.
- Leaving a peat pot rim above the soil. The exposed lip wicks water away from the roots. Bury it fully or peel it off before planting.
Water in and watch the first two weeks
Water right after planting to settle the soil around the roots, then keep the soil evenly moist for the first two weeks while the roots take hold. A little wilting at midday in week one is normal as the plant adjusts. Wilting all day is not, and usually means it needs water or more shade.
Questions, answered straight
7 to 14 days. Start with 1 to 2 hours in shade and build up to full sun and overnight lows. Rushing it is the most common reason transplants fail.
No. Indoor seedlings have soft tissue and no defense against sun and wind. Skipping it can undo 6 to 8 weeks of work in a single day.
That is sunscald, from too much sun too fast. Move them back to shade for a day or two, then harden off more slowly.
After your last spring frost, once nights stay above about 50 F. Cold soil and cold nights stall them even when the days feel warm.
Know when it's time to plant
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