When to Plant Out Tomatoes

I learned something today. I always thought that as soon as you had hardened your Tomatoes off then they should go straight in the ground – assuming there’s no risk of frost, that is. But apparently there is another factor at work, that of overnight temperature.

Apparently, you’re looking for a consistent temperature of not less than 55F (12C) at night. If the temperature is lower than this then the plants may not set fruit and it might actually set the whole plant back.

I find Metcheck to be pretty good for in-depth weather reporting (in the UK at least). It seems that the temperature is still fluctuating to lows of 44F ish or even 38F here in the sunshine state of Bath. But that next week is showing a consistent night temperature over 55F.

So home-sown Tomatoes will stay tucked up under fleece for now. But next week, who knows, they might find themselves in the ground.

How are your Tomatoes doing? Any tips on other factors that affect when to plant out?

23 Comments on “When to Plant Out Tomatoes

  1. Last week’s frosts killed a few of my tomato seedlings :s

    Am being cautious and keeping the remaining ones indoors at night until it’s safe to plant them outside.

  2. Handy piece of advice – I’d been wondering for some time.

    Also, we have various mini plants right now (Marmande and Gardener’s Delight) – some indoors, some I keep putting outside during the day to harden off. The ones that have stayed indoors are doing much better than the others, so perhaps this is best left a little, too. All too easy to get ahead of yourself in the excitement I find!

  3. I don’t have my tomatoes seedlings outside-outside, they are tucked in permanently as they live in the tunnel. But it’s a really useful to be aware of night time temperatures even if you grow protected imho. Night time temperatures very much affect my tunnel, too. And I would wait with planting out especially this year where everything inside (and out!) is later.

  4. I have mine on the front porch, they get some cold. I don’t worry too much about it, when you live in a cold weather area you don’t always follow the rule. If covered with row covers they should be OK.

    I do plant a few cold-set varieties that will set fruit at lower temps, then I know I don’t have to worry too much about them. They get planted out earlier than the regular tomatoes.

  5. I put out about half my tomato plants in my cold frame at the beginning of May and most of them have turned a purplish hue. Whereas most of the one I kept on my windowsill are still looking very healthy. I guess the best strategy is all strategies! Good luck!

  6. I’ve been setting mine out in the sunshine (or cloud) during the day to harden them off, but getting them nice and cosy at night for about a week now and they seem ok.
    I did pick up a nice tip from Fennel and Fern, which was to pop some shredded comfrey leaves in with them when they’re transferred, and even wrap the root ball with a leaf.. haven’t heard of that before so may try it this year.

  7. I’ll plant mine out 1st week of June, until then they’re in the greenhouse. If it’s not warm enough by then I will run out of room!

  8. I am with Jeff that the best strategy is all strategies, but I also use those wall O water (http://www.planetnatural.com/site/wallo-water.html) things. I was skeptical at first because it seems like they wouldn’t get enough sunlight down in there but they have worked great for me for the last couple of years.

  9. I have planted mine out, but on a balcony surrounded by brick walls, which I’m hoping will radiate enough heat at night to keep them healthy!

  10. The ones in my mini plastic grow house are doing really well and better than the ones indoors which are leggy. The grow house is in a sheltered spot by the back door and has the tumble drier vent behind it. It makes use of all the wasted hot air!

  11. I would disagree with that strongly. I set my plants out weeks ago we have had lows in thirties since the plants went out and I even had to cover them for two nights. Currently all of my plants are about 18 inches tall with fruit set. I always plant my plants out this early and end up with ripe tomatoes early in the year without any problems. If you waited until temperatures were consistantly in the 50’s in Illinois where I am you wouldn’t be planting until June and I expect to have tomatoes by the end of June.

  12. The advice I use, from Jackie French, is to wait until the temperature of your soil is about 18C. If you don’t have a soil thermometer (and who does) then that is the temperature that you can sit on your soil for five minutes without your bottom feeling cold.

  13. Used to use METCHECK at work, but find this site http://www.yr.no/place/United_Kingdom/Scotland/Scourie/, based in Norway, far better. It’ll be raining here at midnight, and we’re at a minute under 16 hours between sunrise-set.. Soon be mid-summer.. You can change it for your location..

    I have two unheated greenhouses, and sowed my toms in a propagator on valentines day. They have been REALLY slow to get going, and still are only 3-4 inches tall, added to the frost last week which blackened my potatoes.. Will wait a couple of weeks next year.. A difficult year so far..

  14. Are these blight resistant toms? I got blight last year and was wondering where I could get some resistant plants and if the taste was as good? Any thoughts / help?
    I use the Metoffice i-phone app for forecasts – it’s free, and gives 5 day detailed forecasts based on your current location, it’s very easy to use and has been spot on so far.
    Any thoughts about when I should plant out my butternut squash and sweetcorn?

  15. Well, I never knew that! Perhaps it explains why I have always done so badly with tomatoes. But without a greenhouse, my toms would get terribly leggy indoors for all that time. Oh, my kingdom for a greenhouse!

  16. Don,

    I planted out my sweetcorn and squash at the weekend. So far they’re looking good, apart from a squirrel attack, which has left me one sweetcorn short in my little block of 9. I will have to erect some netting, methinks. Unless anyone has any better ideas?

  17. all strategies here as well….the ones I left indoors the longest caught the slightest frost when put out….others of the same age survived and were 4x’s as big…only put my heater on 3 nights since March…twice in MAY!

  18. I live in the south west of Sweden. My tomato plants are still inside. But I hope to soon be able to move them to my tiny glass house. Thanks for a nice blog!

  19. Here on the English Riviera in Torquay you might have expected that tomato seedlings would be well advanced, particularly with the sunny weather. However, even here the cold nights have taken their toll.

    This time last year I already had some mini plants growing in my greenhouse but this year’s seedlings are only about 1 inch high (2cm). The last couple of days hot weather ( 24c) should see things get a rapid move on!

  20. Thanks Gilbert in Torquay, I was worried after reading most comments, that My little stubbies were unusual for this time of year.

  21. I have two F1 Supersweet Cherries that are about 1m tall and outside in pots. We are in Northern France and nights are between 7 and 12 degrees Celsius. They have been out for nearly two weeks since the last frost and they are covered in fruit. They went crazy after there first rain last week and have been very happy. Fingers crossed that I havn’t pushed them to far too early.

  22. Have you tried growing Roma tomatoes? They are great for making pasta sauce or tomato puree – lots of flesh, and little juice. The biggest plus though is that they a “determinate” plant which means that the fruits all ripen at the same time and you don’t need to keep them staked up or clip off new shoots as you do with the standard tom’s.