Skip to content

Pricking out tomato plants: When and how to do it – check out our tips and tutorials!

Growing tomatoes from seed is an annual ritual with which gardeners get in the mood for the growing year. From February to mid-March, tomato seeds are sown in pots and trays indoors, where it is warm. After just a few weeks, the seedlings begin to crowd each other out, which leads to the next step – pricking tomato plants. When pricking tomato seedlings, the young plants are carefully separated out and placed in their own pots. Here’s how to do it, why it’s important, and tips for turning seedlings into full-grown plants.

Prick tomato plants a few weeks after sowing

Seedlings need to be repotted carefully

Usually tomato seeds germinate between 5 and 14 days after sowing. The seedlings come out of the ground stem first, buried head back. After that, they stand up and begin to grow rapidly. First they unfold the so-called cotyledons, which are rounder than the true leaves. Soon after, a second set of leaves appears – the first set of serrated true tomato leaves. This happens about 1.5 – 2 weeks after germination.

At what time you need to repot the seedlings?

Young plants need rich soil to grow healthy

Some gardeners prick the seedlings before the true leaves appear, but traditionally you wait until they have them. That way, you don’t have to worry about hurting the plant if you accidentally damage a seedling leaf. If it gets damaged after the true leaves have already grown, it’s no big deal.

Do you need to fertilize tomatoes when pricking them out?

Seedlings need regular water and sun

When you plant your seedlings, you will need richer soil. When repotting into new pots, it’s best to use multipurpose compost. Allow the plants to grow in their original seedling soil, then top off the pots with multipurpose compost. Tomato plants will not need additional feed until they are much larger and move to the greenhouse or outdoors.

Prick out tomato plants: What pot size?

Young tomato plants need a lot of light all the time

Tomato plants are about five inches tall when pricked out, so they will eventually need to be planted in pots six inches in diameter. You can plant them in this size immediately after pricking out, or repot them in smaller pots and repot again later.

The advantages of smaller pots and repotting later are saving space and compost and reducing the risk of fungus gnats . These are pesky fly-like insects that like to breed in moist soil. They are a real nuisance to indoor houseplants and seedlings. Their larvae can also damage plant roots.

You can also prick tomatoes in egg carton.

Pricking plants in egg carton is also possible

You can also use egg cartons, toilet paper rolls, paper or plastic cups, or almost any other shallow container that can hold your growing soil. Whatever container you use for your seedlings, make sure it provides good drainage – if the roots of your tomatoes get too wet, they’ll be more susceptible to disease. Cardboard egg cartons are fine for smaller seedlings, but tomatoes will grow out of their shallow cells very quickly.

Pricking out tomato plants: Instructions

After you prick tomato plants, they need to be watered

To pull a single plant out of a box crowded with seedlings, you should work from the outside in. Gently grasp a cotyledon of a plant and carefully remove it from the compost using a pencil, plant label, skewer or other tool.

Prick tomato plants in compost soil so that they get enough food

Use the end of the tool to guide the seedling into the hole of the new pot. You can bury the plant to the bottom of the cotyledons if you like. Roots will form from the buried stem, and if your seedlings are leggy, this is a handy tip to encourage a strong stem. It is not recommended to prick out tomato seedlings that are damaged, stunted or look less healthy than the others.

Grow the young plants properly

After the second set of leaves, the plants need to be pricked out

After planting, seedlings need regular watering to keep the soil moist. They also need light and warmth, so it makes sense to keep them indoors, in a conservatory or heated building. The multipurpose compost is enough to feed them, and they will grow from 2.5 to 5 inches tall to 10 inches tall within a few weeks.

Lighting for your seedlings

Pricking out tomato plants - when and how to do it.

Tomato seedlings need plenty of light to grow into healthy plants. Windowsill light is often not enough, especially in late winter or early spring. If you don’t already have plant lighting, you can set up simple lighting with a grow light. You can mount it on the windowsill, or you can use a traditional light that you hang from above.

Prick out tomato plants a few weeks after sowing

Not everyone has the space for a special light shelf, so a windowsill is bright enough for amateur gardeners to start seeds early in the year. Plus, it’s inexpensive. If your plants’ stems are tall and spindly, that probably means they’re stretching to get more light. Give them light by bringing the lighting to within a few inches of the leaves.