How to Prick Out Tomato Seedlings and Pot Them Up
You’ve sowed the seeds. Now it’s time to plant tomato seedlings into their own pots. Tips on pricking out tomato seedlings, planting them into individual pots, and growing them on using grow lights. Includes an instructional video.
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This is part two of the Growing Tomatoes from Seed Series. The first piece is on sowing tomato seeds and this piece will continue with planting tomatoes in the greenhouse, growing them on, harvesting the fruit, saving seed, and preserving tomatoes.
Growing tomatoes from seed is an annual ritual that gets me into the spirit of the growing year. In February to mid-March I sow them in pots and trays and grow them on in the house where it’s warm. After just a few weeks the seedlings begin to crowd one another out which brings me to the next step – pricking out the seedlings.
Pricking out tomato seedlings means gently separating the young plants and potting them up in their own containers. This piece shares how to do it, why it’s important, and gives tips on growing them on into mature plants.
Growing Tomatoes from Seed Series
This piece includes the third video in the Growing Tomatoes from Seed series, which you’ll find at the end. The first two steps in the process include an introduction to the varieties I’m growing this year, making a simple seedling compost, sowing, watering, and using a heated propagator.
We continue with pricking the seedlings out and planting them into individual pots. Throughout the coming year I’ll be sharing how to grow tomatoes from seed beginning with sowing, growing on, planting in the greenhouse, and finally harvesting.
Just a few weeks from sowing to pricking out
Tomato seeds germinate between 5-14 days after sowing. This time around, mine were up quickly which I attribute to their growing in a heated propagator.
The seedlings tend to come out of the compost stem first, looped back with their heads buried. After that they pop up and begin growing quickly. At first, they unfurl what are called seed leaves, which are more rounded than their true leaves will be. Soon after a second set of leaves emerge – the first set of their more jagged true tomato leaves. This takes about 1.5-2 weeks from germination.
When to prick out tomato seedlings
Though some gardeners will prick out seedlings before these true leaves are out, it’s more traditional to wait until they have them. I’ve tried it both ways and think it’s probably better to wait. That way you don’t have to worry about the plant being hurt if you accidentally damage a seed leaf.
If it’s damaged after the true leaves are out, no big deal. The little plants rely on seed leaves to power them until that point though.
Potting mix for tomato plants
In the first step of growing tomatoes from seed I showed how to make a simple seedling compost to sow seeds into. It was very free draining and lower in nutrients by being mixed with Perlite.
When planting up your seedlings you’ll need richer compost. I tend to use pure multi-purpose compost if potting on into new pots. If thinning seedlings out from pot-sown seeds, I’ll leave one plant growing in the original seedling compost but top the compost up in that pot with multi-purpose.
The tomato plants are likely to not need any additional feed until it’s much larger and growing in the greenhouse or outdoors.
What size pots to plant tomato seedlings into?
Tomato plants are about four inches tall when they’re planted out so they’ll eventually need to be planted in 6-inch diameter pots. You can plant them into this size immediately on pricking out or you can pot them up into smaller pots and then repot them on later.
The benefits of using smaller pots and then up-potting include saving space and compost, and reducing the chance of fungus gnats. Those are annoying fly-like insects that love breeding in moist compost. They’re a real nuisance with house plants and seedlings grown indoors. Their larvae can also damage plant roots.
In my video you’ll notice that I’ve planted the tomato seedlings into smaller peat pots and also 3” plastic pots. The ones in smaller pots are destined for this weekend’s Seed Swap and will need repotting by their new owners in a couple weeks’ time. The ones in 3” pots will be potted on in the next piece, after which they’ll be hardened off and planted in the greenhouse.
How to prick out tomato seedlings
To pull out an individual plant from a seed tray crowded with seedlings you should work from the outside in. Gently take hold of a seed leaf of a plant and gently lever it out of the compost using a pencil, plant label, skewer, or another implement.
Use the end of your implement to guide the seedling down into the hole of its new pot. You can bury the plant up to the bottom of the seed leaves if you wish. Roots will form from the stem that’s buried and if your seedlings are leggy, it’s a handy tip to promote a stronger stem.
Continue working through your seedlings until they’re all pricked out or discarded. I wouldn’t recommend pricking out tomato seedlings that look damaged, stunted, or less healthy than the others.
Growing tomato seedlings
Once planted, the seedlings will need regular watering to keep their compost moist. They’ll also need light and warmth, so keeping them in your house, conservatory, or a heated building is a good idea.
The multi-purpose compost will be enough to sustain them and they’ll grow from 1-2” in height to 4” in a matter of weeks. That’s why it’s important that you sow your tomato seeds not from when the seed packet says, but from using your regions specific climate to guide you. There’s a lot more information on that in the first piece in this series.
Lighting for tomato seedlings
Tomato seedlings need a lot of light to grow into healthy plants. The light from a window sill is often not enough, especially in late winter or early spring. If you don’t already have a plant light set-up, you can create a simple one using a grow-light that clips onto your window sill or by suspending a traditional light from above. I’m using both, and can recommend either.
The clip-on grow light is new to me this year and I’m pretty excited about it. Not everyone has the space for a dedicated grow-light shelf so it makes a window sill a bright enough place for the hobby gardener to start off tomato, pepper, and eggplant seeds early in the year. It’s also inexpensive.
If your plant’s stems are tall and spindly it probably means that they’re stretching trying to find more light. Give it to them by lowering your grow lights to a couple of inches of their leaves.
The next steps
This series on growing tomatoes from seed will continue with repotting, hardening off, and planting out in my greenhouse next month. From that point I’ll be training them to grow up a string, cover nutrition, watering, and pollination, and then show how to harvest and preserve tomatoes in the summer.
That was a lot of seedlings! It's a nice method, I'm new to vegetable gardening and I am inspired by your post. I will try this one and hopefully i'll have healthy seedlings just like yours. Thanks for sharing.
WoW! Your tommies are well on their way, mine aren't even sown yet, well I lie, my Roma were sown last week.
Nice little teasre about the Toothache Plant – interesting! Look forward to seeing how it grows :)
Oh! And I keep forgetting to say Thank You for the 'seed surprise' :)
You're so welcome Mo – I hope they grow for you :)
It's amazing how quickly the tomato seedlings have grown since I put them into modules last week. Fingers crossed for a long hot summer and plenty of tomatoes on the vine!
Oh Tanya, I am so envious of all your seedlings. With no kitchen at the moment, I can't seem to get anything organized, like planting early seeds. I like your method though and will have to give this a try. Next year. :)
A woman can only do so much and you definitely have your hands full Leigh!
The Toothache Plant sounds fascinating, though I don't think I'd fancy an electric shock on my tongue. I'm sure your tomato plants will sell well on your stall, especially after all the tlc you've given them.
Wow…you really take care of your tomatoes!!
My Mum always starts these off for us and they always do really well so I'm happy to let her continue.
We haven't sown our seed yet though…should get around to it this weekend.
The toothache plant sounds ominous…I first though it was to help with pain…but I guess it's really to give you some. I will be interested to see what it looks like and find out what you think about it once it's grown.
You have a very generous mum :) I don't think my mother or even my grandmother have ever grown tomatoes from seed before. It's so much easier to just buy them as seedlings. I'm just a crazy seed lady!
I heard about the toothache plant last year at James Wong's presentation at the Edible Garden Show. He didn't have any for us to try but played a video of some people eating it – very amusing.
Crikey that's going to take you some time to get them all potted up – hope they do well for you.
It took me about an hour to do the Moneymakers and will take about the same time to do the rest. It's not so bad as long as the sun is out :)
I love pricking out and potting on. It's one of my favourite tasks. Haven't managed to sow any seeds except in the ground but am looking forward to getting some sown soon.
It can be quite therapeutic can't it? At least until you encounter the umpteenth tray!
Good luck with your seed sowing Lorna :)
I hope those tomato plants do well on your farmers' market stall Tanya – they ought to after all the TLC they are getting.
Thanks Pat – It would be great to make a bit of extra cash off my seedlings this year. Usually I end up giving most of them away ;)
Those are nice looking plants and should sell easily. Sometimes tomatoes will rot just before they get ripe because they don't self pollinate so when I don't have too many blossoms, I go along and flick the flowers with my finger which helps self pollination. You might try that on half of them and see if it helps, I never tested it as usually I get too many tomatoes all at once.
The problem here isn't really pollination Sunnybrook but Blight, a fungus that is spread in the air and which affects Potatoes and Tomatoes. Have you heard of the great famine in Ireland in the 19th century? It was caused by a massive case of Blight killing off the potato crops…
I am glad we don't have that yet. Our climate is so hot and humid when the fruit sets that often it will start rotting where the seeds should have formed. So I just plant more than I need and end up with too much when all things work.
You're really lucky you don't have it Sunnybrook and it's because your temperature is so warm. Blight thrives in damp but moderate conditions and is a real pain here!
Your seedlings look great and I think you will be most amused with your initial taste of the spilanthes…an amazing little plant whose medicinal value is really quite amazing.
I'm definitely intrigued! Interesting that you say that they have medicinal purposes too Mr. H. I'm going to have to look into that…