Tomatoes in Poly Tunnel

[JohnParticipant]

Hi Charles

I have two questions about tomatoes in a poly tunnel. I am in sunny Exmouth.

The photo shows some tomatoes ready for the tunnel but, since bringing them from a bedroom at home, the older leaves have developed a white tinge. The same with newly planted toms, planted 5 days ago after the late April frosts, although new growth is a darker green. I wonder if this is sun scorch. Although the bedroom area was light, with windows on 3 sides, there was no direct sunshine on the leaves, in contrast to the tunnel which is in an open sunny position. What do you think?

The second photo shows a 4 foot door with a polythene insert below and windbreak mesh above and a permanent 6 inch gap above the door. Night min. emperatures are due to fall mid-week and I wonder if it is better to add a polythene insert for the top door panel at the expense of ventilation during the sunny days. Unfortunately I can’t get to the plot every day and certainly not twice per day. The poly tunnel is new and I haven’t yet got any data on inside night temperatures compared to outside. I do know that it can get very hot during sunny spells if all of the door is polythened.

Best wishes

John

[Don FoleyParticipant]

Hi John,

Looks like sun scorch alright. I get it on my toms when I move them out from the Growlights to direct sunlight.
It wont really do any harm in my experience.
As for the Temperature issue. Toms need reasonably even temperatures – day and night, by which I mean there should ideally not be a big drop at night over daytime temperature. Difficult thing to control but can be done. Have you considered modifying the Pollytunnel and using one of those automatic openers they use in Greenhouses?
I’m sure Charles will have a good idea of how best to tackle this problem.

Don.

[RandAParticipant]

I find that to give a rough estimate the night time temperatures in our tunnel ( 14’x 36′) are approximately 2 degrees c warmer than outside. If you have sunny days the temperature in the tunnel in the day time can go really high 40 C++ if the doors are not open. I agree with Don that the tomato leaves look like sun scorch I would not worry either but if a cold night is forecast then fleece may help. We are not far from you across the water in south wales and I have put my tomatoes out they are doing OK so far. Hope that helps and good luck

[charlesModerator]

Good advice here, only to add John, keep some ventilation by night as that does not lower temperature except in high wind, and it’s vital in May to have ventilation by day.

[JohnParticipant]

Hi All

Thanks for all the advice. The tunnel is a new experience for me and our aim is to extend the season early and late so we don’t need to use the freezer. Charles’ advice on winter salads in the greenhouse has worked a treat so we are looking forward to the results of this new venture.

[JDParticipant]

Hi Don and everyone.
I have been wondering about getting a polytunnel for our allotment to extend the season but have been put off a bit by the fact that I can’t get there twice a day to open and close up and there is no water on site. The soil is stony. I was intrigued by Don’s modification to use greenhouse vent openers. How would you do that? Also what do people find to be the best size in such circumstances and do people get the ‘five ply anti-drip’ covers or just basic. Thanks for your help. I really like the idea of one, but am worried that it would just cremate everything.
Jan

[charlesModerator]

JD I advise a standard polythene cover, nothing fancy, it works here.
I have home made doors with a gap at the top so they can stay closed a lot of the time.
Frazzling is rare in tunnels under say 20 feet long.

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