Tomatoes and Sweetcorn safe to go in Polytunnel?

[marchogaeth]

Doesn't it seem a bit sad that the plants are missing out all the lovely direct sunlight though? I suppose there's plenty more to come in the year (hopefully).

Can you not put them out during the day and bring them in at night? I'm trying to be strict on the 10C rule this year, but the toms are champing at the bit for bigger pots at which put the in out manoeuvre will become too much.

[Kristen]

I have read toms need a min of 10 degrees (like Sparrow says) but then others say they should be ok.

they seem fine

... yeah its the "seem to be OK" that I think is the problem - as that may encourage others to risk it.

It is better not to subject tender plants (Tomatoes, Cucumbers, Peppers, Aubergines) to temperatures below 10C. They will be cold stressed. How serious that is depends on both how cold the temperature fell, for how long, and how often. 9C for an hour is probably not going to be any problem at all. 5C for a couple of hours every night for a week might well be. 2C just once may well be terminal.

Stressed plants will initially stall. They stop growing. They assume that there will be more cold weather, so it takes a prolonged period of warm weather before they get going again. That might well take a couple of weeks - so you could have sown the plants two weeks later and got exactly the same result.

Tomatoes stop metabolising Phosphorus when they get cold. Their veins turn purple, and the leaves take on a purple tinge. Longer term? who knows. I've heard some people say that they had less fruit less during the season, and it tasted less sweet. The plants' immune systems are damaged by the cold stress, so they may be less able to fend of disease later in the season, compared to a plant that is just able to grow flat out, without stress, from the outset.

IMHO it is much better to avoid cold stressing tender plants. Start them off later. Avoid all the hassle of having to try to keep them warm, having to spend time putting fleece over them each night, and so on.

Similarly, at this time of year, for Sweetcorn, Squash and Beans. They grow at the speed of light! then don't need weeks / months of early start. Because they grow so fast they are even more of a nightmare to look after on cold nights as they will, within a few weeks, be big! And they absolutely hate the cold.

I think it is worth starting off a few beans early and sticking them outside, and then growing backups. In a good year you'll get some early beans. But consider the later sowing to be the main crop.

I have heated conservatory, indoor growing room with plenty of heat and growing lights ... but FWIW I started my Sweet Corn (which will be grown in the greenhouse, not outside) a couple of days ago and I am nowhere near ready to sow Squash or Beans (except for a few Dwarf French Beans which will also be cropped in the greenhouse)

[marchogaeth]

^^^^^^
Excellent explanation and advice. I'm about to copy and print off - although maybe I should start a web page with links to useful posts! (Actually, that is an idea!- A FAQ directory - job for you Kristen???)

[Kristen]

Hehehe ... you're all heart aren't you?

[marchogaeth]

Hehehe ... you're all heart aren't you?

I like delegation - used to a class full of really willing helpers!

[Kristen]

"delegation" not equal to "delegation upwards"

[Gillykat]

Great advice re tomatoes. I've got six Gardeners Delight on my living room windowsill and I was wondering when to move them to the greenhouse or polytunnel. I think I'll keep them in the house a couple more weeks and pamper them a bit more

To me (in my first year ever of growing veg!) they look huge! I've always grown flowers in the past and as I said to one of my customers at work yesterday (who also has an allotment) the sowing and getting the seedlings to grow is (or so far has seemed to be!) the easy bit.....but now the inexperience shows and NOW what do I do?

With soup tin for size comparison

[Trix]

Thank you for that great explanation Kristen. I have left one of each tomato variety oustide and they seemed fine - I'll admit that I was starting to think that the 10 degree thing was just people being fussy. But what you have said makes perfect sense and I will now continue to coddle the others for a few more weeks. I might even label them and see how the 'inside' ones compare to the 'outside now' ones by the end of the season

[Penellype]

... yeah its the "seem to be OK" that I think is the problem - as that may encourage others to risk it.

It is better not to subject tender plants (Tomatoes, Cucumbers, Peppers, Aubergines) to temperatures below 10C. They will be cold stressed. How serious that is depends on both how cold the temperature fell, for how long, and how often. 9C for an hour is probably not going to be any problem at all. 5C for a couple of hours every night for a week might well be. 2C just once may well be terminal.

Stressed plants will initially stall. They stop growing. They assume that there will be more cold weather, so it takes a prolonged period of warm weather before they get going again. That might well take a couple of weeks - so you could have sown the plants two weeks later and got exactly the same result.

Tomatoes stop metabolising Phosphorus when they get cold. Their veins turn purple, and the leaves take on a purple tinge. Longer term? who knows. I've heard some people say that they had less fruit less during the season, and it tasted less sweet. The plants' immune systems are damaged by the cold stress, so they may be less able to fend of disease later in the season, compared to a plant that is just able to grow flat out, without stress, from the outset.

IMHO it is much better to avoid cold stressing tender plants. Start them off later. Avoid all the hassle of having to try to keep them warm, having to spend time putting fleece over them each night, and so on.

Similarly, at this time of year, for Sweetcorn, Squash and Beans. They grow at the speed of light! then don't need weeks / months of early start. Because they grow so fast they are even more of a nightmare to look after on cold nights as they will, within a few weeks, be big! And they absolutely hate the cold.

I think it is worth starting off a few beans early and sticking them outside, and then growing backups. In a good year you'll get some early beans. But consider the later sowing to be the main crop.

I have heated conservatory, indoor growing room with plenty of heat and growing lights ... but FWIW I started my Sweet Corn (which will be grown in the greenhouse, not outside) a couple of days ago and I am nowhere near ready to sow Squash or Beans (except for a few Dwarf French Beans which will also be cropped in the greenhouse)

Just a superb post, thanks Kristen. I can add my experience last year to this. I was experimenting with a hotbed, and rather than do the recommended lettuce, beetroot etc, I thought I would be clever and grow french beans, courgettes and tomatoes (Sungold, Chcoloate Cherry and Belle) in it. The beans and courgettes were fine and the tomatoes, planted out at the end of May grew ok, although they looked a bit cold at first, protected only by fleece. I grew more tomatoes of all 3 varieties in the greenhouse, from the same sowing, and some Bajaja planted out later in ordinary soil about 10 feet from the hotbed.

All seemed well until mid August, just as the first tomatoes were showing signs of turning red/yellow. I ate 2 Sungold, and then all the plants in the hotbed got blight. These plants were about 3ft from my friend's pots of Gardener's Delight, which were put out later and did not get blight, and neither did the Bajaja or the ones in the greenhouse.

There was no chance of blight being present in the soil - the hotbed was made from fresh manure topped with bought compost. The only sensible conclusion is that the plants in the hotbed were weakened, probably by getting too cold early on, and were therefore more susceptible to blight than the ones planted a few feet away but put out later.

[Kristen]

I've got six Gardeners Delight on my living room windowsill

They look like the top of the compost is a bit down the pot (on some at least)? I would fill them up so the compost is at the level of the lip of the rim of the pot - maybe 1/2" from the top. You need to leave enough room to be able to water from the top without it running over and going everywhere! but that apart the more the compost the more the roots can grow and develop.

Tomatoes don't mind their stems being buried, so they will be fine, but most plants don't like their stems being buried (planting a tree "deep" is almost always certain death, for example) so don't do that willy nilly with anything else! It is OK to bury a seedling up to its seed-leaves, so if you have others and they still have their seed leaves you can do that. The seed leaves on your Tomatoes are well clear of the tops of the pots, by the looks of your photo (but, just in case I've confused you , Tomatoes wouldn't mind their stems being buried deeper still)

They look like they may not be getting enough light. It might just be the photo, but the leaves look to be quite a light green colour and the distance up the stem between each leaf is quite long. I would expect a plant in good light to be a darker green, and quite "stocky" - short stem-distance between each leaf. But early in the year I don't suppose anyone is growing stocky, dark green, plants as the sun doesn't have any power (it has now, but it didn't have a few weeks ago)

When the roots are showing out of the drainage holes at the bottom of the pot they would be better potted-on into a larger pot. Something about 1/2" to 1" larger all the way around the rootball. So if those are 3" pots?? then a 4.5" to 5" pot, next, would be about right.

As well as roots coming out of the bottom you'll find that the pots get dry quickly - you water them in the morning and by mid afternoon the plants are drooping their leaves, starting to wilt, and if you pick the plant & pot up it will be as light as a feather (and you'll probably water them again ) - that, too, is a sure sign that they need potting-on to a bigger pot.

(Don't stuff them into an enormous pot. Giving them just an inch or so more compost all around the rootball means the roots grow out into that, and fill it with roots. Then you pot-on again to something slightly bigger again which means that you will create a monster rootball and that will enable the plant to take up water, and fertiliser, much more efficiently throughout the season than a plant that was put in a big pot and the roots then grew straight out and around the edge of the pot. Potting on to a slightly larger pot also means that it is very hard to overwater the plant. There is only a little bit of new compost to get wet, whereas in a large pot there is tons of fresh compost, and if that all gets wet the plant is nowhere near big enough to drink all that water, and may well be starved of oxygen at its roots as a result (in effect it will drown)

[Gillykat]

Thank you SO much for all the great advice I'll add a bit more compost tomorrow morning. No roots showing through the bottom (I check most days) but yes, they are quite pale so perhaps it would be best to move them to my greenhouse which probably gets a lot more light than my south-facing living room window. I sowed the seed on March 3rd and since it germinated I've been putting them on the window as soon as I get up every morning and once it's dark outside (or getting dark) in the evening I move them to a table in the corner so they avoid any cold draughts. They're currently potted up in John Innes seed compost.

[marchogaeth]

Just to reinforce the message here about overnight temperatures, I have had 38C in the tunnel the last two days even with all the doors open. On thursday the overnight min was 9C and I was thinking "any day now", Fridays was 3.3 and last night a stunning 1.3.

In previous years I would have probably had the tomatoes out on the basis that I was too busy with everything else, this year I'm just getting up earlier (I like the dawn and the dawn chorus!).

[marchogaeth]

"delegation" not equal to "delegation upwards"

Well I can do that, too. You can choose where to put yourself on that ladder!

[marcofez]

I've had tomatoes in the polytunnel for 2 weeks now and they seem fine. Sweetcorn I've just started chitting.

[Python15]

I've had my toms in the greenhouse (unheated) for about a week and a half. Last night the temp dropped to about -1.5 degs. I think I may have doomed my plants! Had a quick look this morning and the temp was about 4-5 degs in the greenhouse so maybe I will get away with it? I now feel dejected for my plants.