This blog article was inspired by a question from a reader who asked: Do you have some information about the best way to transplant seedlings to the garden? Especially cabbage, broccoli, cauliflower, kale, celery, and lettuce.
We love reader questions and try to answer them as well as we can. And sometimes all of you benefit from a good question. The timing was also perfect since I was transplanting kohlrabi today. All of the other plants mentioned in the question would be the same. Here is the answer to how to transplant seedlings into the garden.
Transplanting seedlings into the ground is a lot of fun, you get an instant garden to enjoy. As a new gardener we’d recommend to start with seedlings from a greenhouse, once you get some experience, then you would feel more confident in starting seeds yourself.
We cover transplanting tomatoes and cucumbers separately since those plants are a bit different, just follow the links. Also if you got multiple plants in one seedling, we have an extra blog post for that as well.
Prepare the soil
The soil for a seedling has to be loose and weed-free, ready to be planted just like for seeds.
In our home garden, we have no-till garden beds, that are loose and ready to be planted at all times. So all it needs is some fork work, to get the occasional weeds out, and racking, to even the mulch layer.
When to transplant seedlings into the ground
The indoor seed starting schedule we use has not just seed-starting times but also planting out times. All of those dates are of course according to the weather. When starting your own seedlings, always consider the planting out date.
A seedling can hardly be too young, once the true leaves are at least the size of the first leaves, it can be transplanted. In my picture above the seedling on the left needs another week or two, the seedling on the right is very much ready. And there is about a month between those two stages, giving us a bit of a window to transplant them.
There is a danger for a seedling to be overgrown. An overgrown seedling is of no good.
A perfect seedling has filled out the pot, but the roots are still not going round, the seedling is not rootbound. My example picture below is right on the edge of being perfect, a few days later and it could start being too late.
I can not stress this enough, do not start seeds too early!
The time on the calendar for your seedling will depend on the plant variety. Cool-weather crops can be planted earlier, warm weather crops need warm weather to grow. You can read more in when to plant what.
Hardening off the seedlings
We have a whole blog article about this important step. Seedlings can not go from indoors right into the ground, they need to get used to the environment they will be planted into.
Head over and read more if the hardening off plants is new to you, or if you are interested in our easy way to do so.
How much room does a plant need?
Since seedlings are already growing, there is no thinning out needed any longer. We plant them according to the mature plant size.
Usually, the seed package tells you how much space that particular plant will need.
Also, the square foot garden book has great information on that. For example plant per square foot 1 cabbage, 1 broccoli, 1 cauliflower, 1 kale, 4 celery, and 4 lettuce.
As a rule of thumb in good soil and a warm climate, you can plant a bit more densely. In a poor soil and cold climate, plants grow better with a bit more space.
I like to place all my seedling pots where I want to plant them so once I start planting there is no planning needed anymore.
Seedlings are also great for succession planting. As you see in my example picture above I give my early kohlrabi a lot of space. This is not because they need it, but because I want to be able to interplant the bed later.
In the middle we have overwintering spinach growing, that was planted here last fall. The kohlrabi is next, and there is space left for cucumber seedlings that will be planted in a month. I have not even started them yet. By the time the cucumbers will need the whole bed, kohlrabi and spinach will be done.
Planting out the seedlings
When the seedlings and the soil are ready and the time is right, we start transplanting the seedlings into the ground.
First, dig a hole big enough for your seedling. I like to use the hand spade for that.
If you have loose soil, the hole does not have to be bigger than the pot of the seedling. However, if you are dealing with heavy soil, making a slightly bigger hole makes sense. You want to encourage the seedling to grow outwards.
For heavy feeders like tomatoes, I also add some compost or warm casting into each hole. Read more about transplanting tomatoes into the ground here.
By turning the pot upside down and tapping on the pot, the plant will come right out. Now place it gently into the hole and gently push back the soil, making sure there are no air pockets around the roots.
If the soil is very dry, which often happens in a dry spring, water the hole first, before planting the seedlings into it. Then water the seedling after planting so the dirt fills in any room between the seedling and the ground. You don’t want to give the roots any chance to dry out.
Protect the newly planted seedling
If possible, choose a calm cloudy day to transplant your seedlings. In our sunny climate that is not always possible. We can have sunshine for weeks. In this case, a plant protection blanket can be used to provide some shade for the seedling.
Since we plant cool weather plants like cabbage, and kohlrabi fairly early, they also benefit from some wind and cold protection. Here I placed a glass jar over them for the first night. If we were to get spring snow, I would also use jars to protect the plants.
Later in spring, cutworms can be a problem, giving the seedling some protection helps, read more about that here.
Once the seedlings are planted and watered, adding mulch is a great idea. It helps to keep the moisture as well as gives the young seedling some protection from the wind.
The more love and care we give the seedling, the better and healthier the plants will grow.