Tomatoes-Temperature

[freddy]

Hi folks. I sowed the first of my tomatoes today, Shirley. Several sources say that once they have germinated, they should be kept at a minimum temperature of 15c. Is that right ?

Cheers...freddy.

[Johnboy]

Hi Freddy,
The minimum for a Tomato Plant is 10C and ideally should never be subjected to a temperature below this point. If subjected to low temperatures it can effect the metabolism of the plant and the final crop can be very different to what was intended.
JB.

[oldherbaceous]

Morning Freddy, i agree with Johnboy on the 10C as a minimum temperature, and this also includes it for nights.

When my old next door neighbour was alive, he always used to put a couple of sheets of newspaper over the plants at night, as he said that was often enough just to lift the temparature by a few degrees.
He would light an old oil stove if very heavy frost was predicted.
And i must say, he did seem to grow some very short jointed and healthy looking plants.

You soon know if the plants are suffering from cold, as they are very much like ourselves and take on a bluey, purpley colour.

[glallotments]

Its why we always hang on planting seeds. We are likely to be early April when we actually sow seeds this year to give them a decent start - they always seem to catch up. It is always so tempting to get going when everyone else is but we don't heat our greenhouse and have found even seedlings kept on a window sill in the house go leggy!

Does anyone else sow as late as us?

[Johnboy]

Hi Glallotments,
A very wise piece of advice throughout.
JB.
PS I wonder how many people take it!

[freddy]

Hi folks. Please excuse my ignorance, but the thing that strikes me is, we can get a frost up until late May which in itself means close to 0C temperatures. Doesn't this mean that we should wait until June before planting out into the greenhouse ?
BTW, I shall be staggering my sowing this year, as last year they all came at once and were finished by late august (if I remember right)
Cheers...freddy.

[glallotments]

Our cold greenhouse usually offers enough protection for seeds sown from April. If a sharp frost is predicted we throw a piece of fleece over the seedlings that need protection. We also have a few propagators in the greenhouse. Its the very low temperatures such as we are experiencing now that are the problem. They also add to the problem by being prolonged spells of extreme cold. It is hardly getting above freezing even during the day and a couple of nights this week it has been at minus 5

Late May is usually when we plant out any young plants that are tender and likely to be affected by a frost. This is after a spell in the cold frame to harden them off.

[Monika]

It's always sooo tempting to start sowing, isn't it? I think most years I have sown my tomatoes by now but this year I have controlled myself and stopped myself from sowing, in spite of the greenhouse being lovely and warm during the day, but it was minus 6 last night outside and just on nought inside the greenhouse. So, as GL says, try not to be too keen this year. Even the forecast to the end of March predicts no daytime temperatures in double figures for us!

[Primrose]

In previous years I would always have sown my tomato seeds indoors by now, thinking it would get them off to an early start. And often I've ended up with leggy plants which had to be planted outdoors and covered with large mineral water bottle cloches so I don't think my enthusiasm to sow early really gained me anything. This year I won't be sowing indoors until early April where overnight temperatures should be still hopefully be warmer than in a greenhouse. Once you start off with a sickly seedling it never ever really recovers, even when the weather gets warmer but it's taken me many years to overcome my impatience.

[richard p]

i had the first chickweed and dandelion from the tunnel in a ham sandwich for lunch today so have set some toms going in the propagater.

[ken]

I agree with all the comments about keeping the tomatoes above 10C - and I still start mine off early, in the house,on a south-facing windowsill. Come May, I give myself a bit of a nightmare, bringing tomatoes and peppers from the greenhouse and back into the house when low temperatures are threatened. But generally it works well. Incidentally, I picked up an American tip some time ago, from the states where they have very short growing seasons. Apparently it is very difficult for them to avoid having leggy seedlings, but they plant them out deep, to just below the first leaves. Tomato stems are capable of putting out roots, and so they develop a stronger root system. Do a similar thing myself: out greenhouse tomatoes go into big pots which initially I only half fill with compost. Then, when the plants are well established, I top up with more compost.

[Primrose]

I normally sow my tomatoes straight into individual pots. Last year I started them off in trays and into filled pots. I now better understand the plants can grow additional roots, but if I sow in trays this year, and then put the small seedlings into pots only half filled with compost (with a view to stopping up later) will the lack of light & shade caused by the sides of the pots make them leggy? I worry that the disadvantage of this system is that there is less compost downwards for the roots to expand into so they might start growing upward. Wouldn't this be a disadvantage when the plants are finally planted out into the borders?

[tiamaria1]

When I sow tomato seeds I sow them in a seed tray and prick out when they have 2 true leaves. But I plant them quite deep into the pot, so the leaves are just above the surface of the compost, at the pricking out stage and do the same when I transplant them.

[John]

Best to start sowing about six weeks before you think that you can safely plant out in their final positions.

[PLUMPUDDING]

I plant the seedlings deeply like tiamaria and they root all up the covered stem. This is also a good trick if they have gone leggy from too little light.

When I plant them in their bottomless pots in the border I also plant them deeply so the top of the plant comes only half way up the pot. I've found this gives early protection from cold nights until they have hardened off and then I fill them to the top with compost when the plants have grown higher. They make extra roots into this all up the covered stem making nice strong plants and they don't seem to notice the slight reduction in light until they are above the pot sides.

I've left the spare seedlings that I've not pricked out in the open greenhouse to see what effect the much lower temperatures have on them. It was - 1C the other night and they were all lying down the next morning, but I watered them and by afternoon they were all upright again, with a bit of a strange colour. It has certainly checked their growth dramatically, but I think I'll pot up one or two and see how they perform with regard to flowering and fruiting compared to the pampered ones in the propagator, which I'm starting to harden off but keeping covered at night. I've also installed a lamp over the propagators this year and am giving them an hour in the morning and an hour in the evening and this seems to be keeping the plants nice and stocky.

You might think I'm potty, but I gently brush over the plants or blow on them to move them about as I read that this encourages stronger plants - I think its called thigmomorphogenesis or something like that. I'll have to look up the spelling again.