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Early Care of Transplants
On this page find information about the important bridging step between rearing plants indoors, in a cold frame, or in a greenhouse and transplanting them to your home vegetable garden, including:
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- Why hardening vegetable starts is important before planting them outdoors.
- A complete description of the process of hardening off vegetable sprouts and starts.
- How to care for vegetable plants during the hardening process.
- Precautions, hints and tips about successfully moving transplants outdoors to your home vegetable garden’s beds.
About Hardening Transplants
Hardening is a simple way to protect tender vegetable starts that you’ve reared indoors. After all, you’ve spent weeks rearing your seedlings.
Protect your investment by hardening them off prior to planting outdoors. Hardening helps young, tender vegetable starts you’ve reared indoors adjust to early-season cold temperatures, changing conditions and overnight frosts.
Protecting Seedlings
Seedlings grown indoors, in a cold frame, or in a greenhouse with nearly ideal, constant temperature and humidity conditions need time to adjust to the real world. Help them acclimatize to outdoor conditions prior to planting, using the process called “hardening” to give young plants a great start outdoors in the garden.
Starting 7–10 days before the intended date of planting, move the seedlings outdoors during mild days to a protected, shady area with plenty of indirect light. Too much direct sunlight will burn their foliage, while too little will slow their growth.
For the first 2–3 days, bring the seedlings back indoors during cool evenings, or return them to a cold frame and close its top.
As the plants begin to adjust, leave them outside during the evening, covering them loosely with breathable fabric supported above the plants on stakes or a wooden frame [see Row Covers].
Until temperatures have moderated and are predictably warm, temporary frost protection may be necessary. Cover the plants during any cold snaps, or install hot caps, row covers, or other protection.
Cold Frames and Greenhouses
Those that garden in cold-winter or short-season climates benefit from season-extending vegetable growing practices and by building and using one or more cold frames or a greenhouse [See: Building a Cold Frame].
Both cold frames and greenhouses collect the sun’s energy, but cold frames also are set deeply into the soil, where temperatures are less cold than at the surface.
If you live at high altitudes or in cold regions with long winters, growing a full season’s vegetables in your home garden is far easier with either structure.
Care During Hardening
Care for your seedlings during the hardening process in gradual steps, allowing them to become used to outdoor conditions.
Keep plastic or other coverings from touching the foliage of the tranplants; water condensing on the cover will cause fungal disease on the leaves or freeze and kill the plants’ foliage.
Leave the covering in place on cold days or whenever rain, hail, or sleet occur, but lifted it during the morning hours on mild, warm, or sunny days.
After a few more days, move the plants to a sunlit spot protected from wind, and limit the period they are covered to cold-night protection. The plants will adjust quickly to the outdoor conditions of your garden.
As a final step during the last 2 days prior to planting, position your unplanted vegetable starts in the garden itself. They still may need nighttime protection. Featherweight fabric row covers or waxed-paper hot caps and heavy straw mulch are ideal ways to keep soil warmth constant as temperatures swing up and down. [see Row Covers].