planting out temperatures

[bluebellParticipant]

Having just acquired a poly tunnel I have been trying to establish what the requirements are to plant out my tender plants. It appears that the terminology is almost as miss leading between frost free terms as it is between compost and manure…

So last frost dates are quoted but of little direct relevance to a poly tunnel or to planting out tender plants. I was therefore looking for an actual temperature, which I can look for as a steady minimum on a max min thermometer and was quite surprised to find that for tomatoes it is 10 degrees Celsius and for peppers and aubergines 15. So in both cases quite significantly above ‘frost free’.

Also I didn’t realise that tomatoes stop growing over about 35 degrees Celsius.

When there has clearly been some research done in to this I find it odd that instructions are often so imprecise as whilst I am sure that there are other factors such as humidity wind etc having this level of detail must help in the production of healthy crops and a good yield?

[charlesModerator]

Fair point but the other side of the coin is that quoting a “best temperature” range for crops is somewhat arbitrary and potentially misleading.
The 10C you give for tomatoes is, I think, too high. After planting out in May, mine are often subjected to 3-8C during the first 1-4 weeks in an unheated tunnel, depending on each spring’s weather. They thrive.
Also the temporary halt above say 35C is only temporary, though it shows how worthwhile it is to ventilate in hot weather. So you are doing good research but I suggest using it as guide only.
Aubergine and pepper are indeed more warmth dependent.

[bluebellParticipant]

Thanks for your common sense and experience as always Charles. Although not mentioned I figure that the exact temperatures are generated by the ‘industrial greenhouse’ growers, where maximum out put is the mantra.
I am sure at the end of the day the only way to go is to measure daily and record as you do, but wanted a base line to start from.

[LeifParticipant]

Whilst I have far less experience than Charles, I too found that tomatoes could tolerate temperatures down to about 5C at night for short periods. Chillis – Capsicum annuum – really do not like it below 10C and will take time to recover. Capsicum chinense is even more sensitive. C baccatum and C. pubescens are more tolerant, and plants (not seedlings) can even survive light frosts. Courgette and squash seem unharmed by 5C at night.

[RhysParticipant]

Where tomatoes are concerned, I’ve been told by very experienced growers that a limited cold shock actually increases the yield. I must say I’ve never had a bad crop leaving plants outside overnight with nighttime temps of 6C in late April or early May.

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