When Should I Transplant My Seedlings?

You planted some seeds and they sprouted! You got in the habit of checking on them each day and you kept them alive. But what do you do next? Are they getting too big for their seed starting trays? How do you know when to move them to a bigger pot or transplant them outside? Don’t worry, I have an easy three-step process that will make sure your plants are ready to move on up!

Step 1: Do they have a second set of true leaves?

When a plant sprouts, the first set of leaves may not look like the regular plant leaves. These “cotyledon” leaves are usually similar for all plants in their plant family and can be very different from what you might expect. You don’t want to transplant your seedling until it has grown at least two sets of true leaves beyond those first sprouts. Depending on the variety of plant, it can take a couple weeks or a couple months for your seedling to get to this stage.

Don’t rush! Your plant needs to have some established leaves to survive the inevitable damage to its roots when you move it from one pot to another or from inside to outside. Sometimes the cotyledon leaves will drop off, making it even more important that your seedling has at least those four leaves to keep it going until it can grow more. The shock of transplanting can cause the plant to delay sprouting new leaves as the roots recover, so make sure it has enough foliage to survive the experience.

Step 2: Its height is twice the pot depth

Most plants grow a root system that is about two-thirds as deep as the plant is high. So, if your plant is more than twice as tall as its pot is deep, you know it’s ready to move up or out. Some plants can handle a lot of growth with relatively shallow roots, but in general, if your plant is looking top heavy, it’s time to get it in the ground or into a larger container.

Similarly, when you are choosing a container for your seedling, or digging a hole to transplant it outside, make sure to give your plant room to grow. It needs loosened soil or pot depth to fit the existing roots and space to grow into. Depending on how long your plant will stay in its new space, you may want to add some nutrition to the soil as well. Putting a scoop of compost or other soil amendment into the container or hole can give your seedling a boost and help it through the shock of being transplanted.

Step 3: Check for escaping roots

If you find roots coming out the drain hole of your pot or you can see the roots close to the top of the soil or coiling around the pot’s edge, your plant is becoming “root bound”. If the roots get too tangled up, it can permanently damage the plant or even kill it. Sometimes while transplanting you’ll want to loosen up the root ball and make sure the roots are growing down and out rather than around in a circle.

However, adjusting the roots too much during transplant can damage or even kill some plants. Make sure to get your seedlings in a larger container or outside before the roots get too damaged by hitting the edge of their container or getting tangled up with their neighbors. It’s generally better to transplant too early than too late.

So, now you have the three step process for figuring out when you should transplant your seedlings. This process also works for house plants, container gardens, or pretty much any plant that might not have enough space where you are choosing to grow it. As you go through each step of the process, look for clues that the plant might not be happy. Does it need to be watered frequently but still looks droopy? Are the tips of the leaves or branches turning colors or shriveling? Has the plant stopped growing rapidly? Any of these could be signs that the time to transplant is now! So, step through the process and make your transplant plan today. Good luck!