Updated: Apr 13, 2021
Hardening Seedlings Before Planting
Spring is here finally, and we can get ready for this growing season! If you start your seedlings early indoors, you'll need to harden off your seedlings or your plants that you have grown inside over the winter months. This is a crucial step to keep your seedlings healthy and robust.
Hardening off seedlings can be a time-consuming task, but it will be worth it once you complete this task. After taking the time and energy to care for your seedlings as they start to grow, the last problem I want to have is to put them out and get sunburned. That could cause them to be stressed or even die. When I was beginning, I learned that the hard way, I watched myself fall behind on the growing season and my precious seedlings were almost completely wiped out.
It's like our skin after the winter months where we haven't had much sun. After winter going out into the sun, working on one of your spring projects on a sunny day, all of sudden, you happen to look at your skin and notice you are almost as red as a lobster. Well, your plants are similar to your skin when they have been growing under grow lights. Taking them directly into the sun will burn them because they haven't built their sun-blocking abilities. The sun is mighty, so your seedlings can not go from grow lights to direct sunlight all day long.
What is Harden Off Before Transplanting
Hardening Off is the process of allowing your seedlings to acclimate to the sun. Without this process, you can severely damage your seedlings. Not only the sun but the weather as well. Even if you have been growing in a sunny window or a greenhouse, you should still be hardening off your seedlings. Even in these instances, the sun is not as powerful through the glass or the greenhouse material, so you still need to harden off your seedlings. If you don't, you may incur damage to your seedlings.
How to Harden Off Plants and Seedlings
Hardening Off your plants and seedlings can take up to a week long. Firstly, I suggest not placing your plants and seedlings out in under forty-five-degree weather, especially your warm-weather crops, like cucumbers, melons, and squash, for example.
You will want to start with only a couple of hours in the direct sunlight. So if you have an area outside that will shade your plants after a couple of hours of sun, that would be a great location. The morning sun is best because it is lower in the sky, so it's less direct sunlight than the afternoon. Bring your warm-weather crops in overnight if it will be below fifty degrees and forty-five degrees for the cold-hardy crops. Please don't place your crops outside when it's windy because they are not strong enough to withstand strong winds. If you have a location where you can get them off the ground, that would be best so that rabbits and mice can't get to them. It will also help with keeping slugs off your seedlings. Each day add two more hours in direct sunlight until you get at least ten hours of direct sun. So within five days, you can be ready to plant your seedlings.
Every plant may vary on their needs to get acclimated to the weather and sun. Some may take less time than five days. A good indication is to look at the leaves. If the leaves are thin and limp looking, they have not built up their sun resistance. As your crops are becoming acclimated to the sun, you can notice that the leaves will thicken and not be limp.
Another good way to harden off your seedlings is if you have a raised bed with greenhouse plastic on a top that opens up so you can open it daily for the necessary amount of time.
How to Harden Seedlings Fast
The fastest way to Harden Off your Seedlings is to place them outside on a cloudy day. I would be watching the weather for two or consecutive days of cloudiness so you can put your trays out and leave them all day long. Doing it this way will significantly decrease the amount of time you spend acclimating your seedlings. Plus, you don't need to constantly run your trays in and out of the house for the acclimation period.