How To Harden Off Seedlings: A Guide To Outdoor Success

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Have you bought seedlings or plants over the last few weeks that you’re eager to get into your garden? If so, did you think about hardening them off before planting them?

This text is a translation from Noovo Moi.

Hardening off is a crucial step for any seedlings or plants that were started indoors before being moved outside.

Indoor temperatures are vastly different from outdoor conditions, and an abrupt transition could seriously shock your plants.

Here is why you should always acclimatize your seedlings and plants before they make the big move.

Significant Damage

Seedlings or plants that haven’t been properly hardened off can suffer major damage to the point where they might not survive.

Sunburn is a common issue: leaves can become discoloured, or white spots may start to appear. The leaves can even turn brown, which means they are scorched. Their stems also become brittle and easily breakable.

Additionally, when seedlings or plants aren’t well-acclimatized, they can experience transplant shock, which stunts their growth for several days or even weeks

The Best Time to Plant Your Seedlings

The best time to plant your seedlings or plants is when outdoor daytime temperatures consistently reach 15°C or higher. If the temperature drops below 15°C at night, you should bring them back indoors to prevent the leaves from freezing.

But remember: you need to gradually acclimatize them before permanently planting them outside.

• Days 1–5: Start by placing them in an area sheltered from direct sunlight for 3 to 5 days.
• Days 6–10: Move them to a partial-shade location for another 3 to 5 days.
• Final Step: After that, you should be good to move them into full sun.

Useful Accessories for Planting Your Seedlings