How and Why to Harden Off Seedlings Before Moving Outdoors

Preparing Seedlings to be Planted Outdoors Hardening off seedlings gradually exposes the tender plants to the wind, sun, and rain, toughening them up by thickening the cuticle on the leaves so they lose less water when exposed to the elements.

Why is it important to harden off seedlings before transplanting?
When should I harden off seedlings?
How big should seedlings be before hardening off?
Do all seedlings need to be hardened off?
How do you harden seedlings before transplanting?
Is it OK to leave seedlings outside at night?
What happens if you don't harden off seedlings?
What temperature will kill seedlings?
Why are my seedlings tall and skinny?
How do you stop seedlings going leggy?
What do true leaves look like on seedlings?
How do you handle seedlings?

Why is it important to harden off seedlings before transplanting?

One key concept to successful transplanting is when a plant has “hardened off.” Plants growing outside naturally acclimate to changing weather. ... 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.

When should I harden off seedlings?

Hardening off should take a minimum of a week and may take up to two. Suddenly moving plants from a stable environment to one with wide variations in temperature, light and wind can seriously weaken plants. For most plants, start hardening off about a week before the final frost date for your area.

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.

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.

How do you harden seedlings before transplanting?

Here's what to do:

Check your seedlings' frost dates. ...
Stop indoor watering or fertilizing. ...
Choose your first hardening off spot. ...
Place your seedlings outside for an hour. ...
Move your plants back indoors. ...
Lengthen the hardening off time. ...
Protect your seedlings as needed. ...
Extend nighttime hardening off hours.

Is it OK to leave seedlings outside at night?

Step 3: Leave seedlings outside overnight

Eventually, allow your plants to stay in full sun and outside overnight as long as night temperatures do not drop below freezing. ... They can't stand below-freezing temperatures, even after the seedlings are hardened off. So continue to bring indoors if nights remain cool.

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.

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.

Why are my seedlings tall and skinny?

The most common cause of legginess is an insufficient or uneven access to light. When the light source is too dim or distant, seedlings grow quickly in height to get closer to that light. As the seedling gains height, it sacrifices in girth and strength, resulting in thin, pale, fragile, stretched-out stems.

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 do true leaves look like on seedlings?

When a seedling sprouts, the first leaves that appear are not “true” leaves, but rather “cotyledons” or seed leaves. They sometimes still have the seed coat on their tip as they grow upwards. ... True leaves resemble the look of the adult leaves whereas cotyledons are simple and nondescript.

How do you handle seedlings?

Lift each seedling carefully, only ever handling them by their leaves, never the delicate stems. Carefully feed the roots right down into the hole then gently firm the seedling in. You can bury some of the stem if the seedlings are looking a little leggy and drawn. This will help to support them.