Planning tool

Hardening-Off Transplant Planner

Use catalog transplant windows, indoor-start duration, crop season, local frost risk, wind, water, and soil warmth before moving seedlings from trays or pots into beds.

Planning tool

Current hardening plan

April 15 to April 29 transition

Roma Tomato hardens off for 14 days before an April 29 transplant target.

14-day hardening ramp Static hardening ramp shows shade, filtered sun, wind exposure, and transplant-day readiness.
Start outsideApril 15
Transplant targetApril 29
Ramp length14 days
Night checkAbove 50F

Inputs

Default dated example
With the default April 15 last frost and a 14-day tomato transplant offset, target transplant day is April 29 and hardening off starts April 15.
Catalog transplant window
Each transplant-capable entry stores a transplantAfterLastFrostDays value so cold-ready and frost-sensitive crops can be separated before planting.
Hardening duration
Use a short daily exposure plan before transplant day; long indoor-start crops often need extra attention because they have spent more weeks under protected conditions.
Weather and soil readiness
Check cold nights, wind, rain, and warm-season soil before treating the catalog transplant window as ready.
Water and wind exposure
Reduce watering only enough to slow soft growth, keep seedlings from wilting, and protect them from wind before and after transplanting.

What it returns

Planning guidance

Two-week transition
Two weeks before planting outdoors, UMN recommends starting seedlings outside for a few hours in the shade during the warmth of the afternoon, protected from wind.
Daily exposure
Each day, leave the plants out a little longer and expose them to a little more direct sunshine before they stay outside full time.
Shock reduction
Hardening reduces the plant growth delay after transplanting, otherwise known as transplant shock.
Watering reduction
Slightly decrease watering, but not to the point of wilting; UMD also says reduce frequency without letting plants dry enough to wilt.
Transplant-day weather
Transplant in late afternoon or on a cool, cloudy, calm day, and water plants well before transplanting.
Cool and warm night thresholds
Cool-season crops should come inside below freezing; warm-season crops should come inside when nights are expected below 50F.
Exposure boundary
Do not put tender seedlings outdoors on windy days or when temperatures are below 45F, even if the calendar window looks close.
Warm-soil boundary
Warm-season crops establish best after frost danger has passed and soil is sufficiently warm, above 60F.
Aftercare moisture
After transplanting, protect tender plants from wind and direct sun for a few days and keep soil uniformly moist but not saturated.

Regional transplant timing fallback

Cool-season hardening candidates

Warm-season transplant candidates

Long indoor-start candidates

Supporting planning paths

Source basis