26 May 2019

Beginner's guide to: potting on tomato seedlings

I was deliberately late in sowing tomato seeds this year (hellooo urban flat, shady interiors, minimal windowsill space). A good decision as it turns out because all seeds germinated leaving me with 63 tomato seedlings to find room for. (Now 58 as I culled a few.)

So I had 5 or 6 seedlings in each small 9cm pot that needed to be potted on into individual pots. Doing this gives each plant more root room to grow and should be done when the seedling has its first true leaves. (Plants that aren't potted on quickly enough will adapt to the smaller environment and never reach their full potential.)

I used to be very wary of potting on little seedlings in case I damaged the plants but experience has taught me that it's really very easy. And sowing several seeds to a pot at the start saves both space and compost in the event that not all seeds germinate. I potted all 58 plants on yesterday; for info, here's how it's done.

Getting ready to pot on seedlings

Have all materials ready and nearby:
-  A large sheet of newspaper as a working surface
-  A bag of multi-purpose compost. (I'm using Dalefoot's new compost specially for tomatoes.)
-  Pots for potting on. Mine are all reusable plastic, either 7cm or 9cm square or 8cm diameter round.
-  Gloves (I quickly load up the pots with compost using my gloved hands rather than a trowel)
-  A dibber for making holes. Purpose made, a stick or a spoon - gardener's choice.
Labels, one for each plant.  I also date mine for future reference.

Work in the shade to minimise stress on roots. Sounds obvious but needs to be said. On a hot day, dry heat is a death knell for plants.

Don't water the seedlings beforehand, it will make the task much messier and wet soil will make it harder to disentangle the roots.

Work on one pot of seedlings at a time. I had five seedlings in each pot so filled five small (7cm) pots with compost and made a deep well in the centre of each with my dibber.

Using dibber to make holes in compost

Work quickly. Carefully tip the seedlings out of their pot onto the newspaper. The roots are now exposed so you want to get the plants into their new pots asap!

Hold the seedlings by one leaf, (never the stem!) Pick up one seedling, gently detach it from the clump and lower it into the new pot of compost. Use the dibber or a pencil to ease the roots into the hole.

Easing seedling into new compost

With tomatoes, bury the stem as far as the plant will allow, almost to the plants lowest leaves - the plant will make more roots this way.

Water the plant to settle the roots.  Do this gradually, not as a deluge from a watering can. Once the soil is moist, or water drips from the bottom of the pot, stop. Allow the pot to drain, don't leave it sitting in a puddle.

Label the plant and make a note of the date it was transplanted.

In the heat of the day, keep in dappled shade to allow the plant to settle, at least for the first few days.

Job done - at least until it's time to pot on again into final large pots.

Yesterday's hot sunshine was followed by a warm night so I was able to leave my tomato plants out on the balcony overnight. The newly transplanted were kept away from strong breezes and have been brought back into the light this morning.

I'm guessing that many readers of this blog will know all of this already but this is for those that don't.  In conversation with people who have yet to try growing anything, I'm often told (for example), "I'd love to grow tomatoes but don't know where to start."  I hope this will help.


  1. I have move our tomato seedlings last weekend. Hoping all seedlings will grow healthy. Such a shame I need more space to put our seedling tray.

    1. Yes, me too, Endah. I have my tomato plants on trays on my (tiny) balcony so there's no room for anything else! I'm sowing all veg seeds direct into the soil this year to save space. Never enough room for all I want to grow.

  2. I have about fifty tomato seedlings to pot on so this article was really useful, especially burying the stem to the lower leaves.xxx

    1. I'm really pleased that you've found this post helpful, and that it's not just me with so many tomato seedlings, Dina! Do you usually grow that many tomatoes, I wonder; I don't but am now imagining what I can do with all those tomatoes if the plants grow well! :D xxx

  3. Some excellent advice Caro especially your mention of working in the shade. 58 seedlings sounds as if they could potentially produce a seriously large number of tomatoes 😀 Will you be giving some plants away? How are you finding the Dalefoot compost? I've not grown tomatoes from seed for a while now but am using their compost for seeds for all my seed grown plants this year. I've been most pleased with the results so far.

    1. Thanks Anna. Yes, 58 sounds a lot! If I can't find homes for the extras, I'll plant them in beds in the community garden where I'm pretty sure people will help themselves. :D I'm completely won over by Dalefoot Composts across the range. I love the texture and have been using them for a while now, all with excellent results. I'm hoping that as the range becomes more popular, the price may come down slightly!

  4. A useful post and good pictures. I only grow about a dozen tomatoes so I sow one seed per 9 cm pot and generally don't repot them. xx

    1. Thanks Flighty, I was hoping that readers might find this post helpful, particularly anyone new to growing from seed. (I know that you're experienced so good to have your feedback.) However, a question: do you pot your seedlings from 9cm pots into larger pots on your windowsills or plant them out into the soil on your allotment? Caro x

    2. You're welcome. They get planted out on the plot once they're at least six inches tall and after they've been hardened off for a few days. xx

    3. Good to know, thanks Flighty.

  5. so many Tomatoes, so little time. (and room). :-)

  6. Hoping all seedlings will grow healthy


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