This spring, many of you are growing the seedlings yourself. This is a fairly simple process that requires only minimal equipment.
In a few weeks, you can grow the seedlings to a size suitable for planting in a garden, container or seedbed. Before moving young, young seedlings into the garden, they must first be hardened or accustomed to outside temperatures, sunlight, wind, and other environmental factors.
Plants taken directly into the garden from a controlled environment are most often scorched by sunlight and wind and are either killed or severely depleted.
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The hardening process, also called “hardening off,” turns tender and succulent plants into hardy, stronger-stemmed and leafy plants that are resistant to wind and sunlight.
This process promotes the formation of a cuticle on the surface of the leaf and stem, which reduces water loss. If the transplants are the right size, take them outdoors to a shady, sheltered place.
Some guidelines for starching:
- Keep the transplanted plants in the shade and gradually expose them to sunlight for a short time each day.
- Do not remove the transplant on windy days or at temperatures below 45 degrees (this includes cool vegetables).
- In the first few days, take the transplants back at night, unless the temperature is very mild.
- Reduce the frequency of watering, but do not allow the plants to dry completely.
- Do not fertilize during the hardening period.
The hardening process should begin one to three weeks before the vegetable transplant is ready for the garden. The time it takes for the plant to fully solidify for planting depends on the conditions under which it was grown.
Do not rush the hardening process, because even if the transplant survives the planting, growth and yield will be delayed and the yield will decrease. Let the condition of the plant prevail.
Another way to harden grafts is to place them in a cold frame. A cold frame is a simple structure that protects plants from the wind and uses the sun for heat.
Cold frames allow the sun to transmit energy through its cover, where it can be stored as heat in the soil. The heat is slowly released overnight to keep the transplanted plants warm.
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Cold frames are most often built of treated wood above the ground, although permanent frames can be made of cast concrete or masonry blocks. In the past, lids were made of wood and glass, but nowadays they are made of plexiglass or double-layer transparent plastic. Doubling the plastic creates a dead space for further insulation.
The lid should be hinged for easy opening as a source of ventilation and temperature control. Place cold frames away from trees, near a water source and facing south.
Adjust the cold frame cover every few days to help the plants harden. On mild, sunny days, you may need to open the lid wider. If very cold temperatures are expected, return the transplants indoors.
Cold frames can also be used to grow cool seasonal crops (e.g. lettuce, radishes) to harvest before the normal planting season. You can extend the growing season to November or December if you grow the same plants in a cold frame.
When hardening is complete, you can place your plants in the garden. On a cloudy day or late afternoon, transplant the plants and keep the plants in the shade for two to three days until they have settled.
Even hardened plants can wither if exposed to full sunlight at first, although they usually recover within a few days. Water the plants as needed. Seedlings grown in peat pots or peat pellets can be planted directly in the garden.
Break down the bottom of the peat pot to improve root penetration and drainage and remove the top edges of the pot that extend above the ground line. These edges can act as a wick that moves water away from the root zone.
Growing your own vegetables from seed can be fun and rewarding, just don’t forget to get used to new transplants properly outdoors.
P. Andrew Rideout is the Horticultural Extension Agent at the University of Kentucky at the Henderson County Extension Office. You can reach him by email at email@example.com.