How to harden off seedlings

An intermediate home, such as an unheated greenhouse or cold frame, is a great tool for hardening off. Place seedlings and plants into the structure for a couple of hours on the first day, then gradually increase the length of time they are in place by two or more hours per day.

How big should seedlings be before hardening off?
When should I start hardening off seedlings?
Do all seedlings need to be hardened off?
What happens if you don't harden off seedlings?
Will leggy seedlings still grow?
How do you stop seedlings going leggy?
What temperature will kill seedlings?
Can I put seedlings in direct sunlight?
How important is hardening off seedlings?
Do leek seedlings need to be hardened off?
How can I harden my plants without a cold frame?
How do you harden a plant before transplanting?

How big should seedlings be before hardening off?

The general rule of thumb is that when a seedling has three to four true leaves, it's large enough to plant out in the garden (after it has been hardened off). When you plant a seed, the first leaves to emerge are the cotyledons.

When should I start hardening off seedlings?

Begin the hardening-off process 7 to 14 days before the date you will plant your seedlings outdoors. In spring, most seedlings are typically planted outdoors after the last frost date. However, cold-hardy plants can be planted outdoors two to four weeks before the last frost date.

Do all seedlings need to be hardened off?

While nursery plants that are displayed in full sun don't need to be hardened off, smaller seedlings that live under a shade structure are susceptible to shock if not hardened off properly. You'll have the best chance at success if you harden off vegetables, herbs, and flowers before planting them in your garden.

What happens if you don't harden off seedlings?

3) Harden Off Your Seedlings: If you don't harden off your indoor seedlings before planting them outside, they will suffer shock from the brutal sun. Without the opportunity to adjust first, they'll get sunburn and might even die.

Will leggy seedlings still grow?

Most leggy plants become sturdier once they are growing outside. ... Put a small fan next to your seedlings on a timer so that the plants are blown in the breeze for a couple of hours a day and gently passing your hand over the tops of seedlings a few times every day to stimulate stronger growth.

How do you stop seedlings going leggy?

You can reduce the changes of the seedling becoming leggy by ensuring you germinate it in the lightest possible conditions. Also turn the container every couple of days so the light is not constantly drawing on one side of the seedling.

What temperature will kill seedlings?

The general rule of thumb is that most plants freeze when temperatures remain at 28°F for five hours. Of course, there are exceptions to this rule. Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F.

Can I put seedlings in direct sunlight?

Initially place seedlings outdoors in a sheltered spot – protected from wind and direct sun. Each day following, expose plants to another 30-60 minutes of filtered sunlight. Work your way up to giving plants direct morning sun, followed last by noon-day sun.

How important is hardening off seedlings?

Hardening-off is important because it reduces plant stress. It can sometimes take several weeks for newly transplanted plants to really take off and begin growing. ... In the spring, it's common practice to gradually accustom greenhouse vegetable seedlings to full sunlight and drying winds before planting them.

Do leek seedlings need to be hardened off?

Free draining soil is essential as the winter months can cause rot problems. Adding a good layer of well rotted manure to the final bed in autumn will give the very best results. Leeks are really tough and shouldn't need hardening off if planted straight outdoors unless extreme weather is expected.

How can I harden my plants without a cold frame?

If you don't have a greenhouse or cold frame, just set your plants outside for increasingly longer periods of time. Towards the end of the hardening off period you can use fleece or row covers to protect foliage against the chill of night.

How do you harden a plant before transplanting?

Begin hardening off on a still, cloudy day when temperatures are fairly steady. Water plants before they go outside. Place them into your sheltered spot for just two hours on the first day. The next day, leave them out for two more hours, with perhaps an hour's direct sunshine in the morning.