Blight is typically caused by airborne fungal spores in wet conditions on the leaves.
Well directed watering at the base of the plants is not going to cause blight.
As long as the surface of the soil isn't staying damp. If you water 'sub surface' using half buried water bottles or plant pots or a proper subsoil irrigation system then I agree, you probably won't get blight on them, just tasteless tomatoes and/or split skins from over-watering. But if you keep watering and keep the soil surface damp by doing so, you raise the humidity locally and increase the risk of blight - given that a wet summer in itself makes blight more likely. In this heat, even watering the surface has little impact, the water evaporates very quickly for one thing and the spores are not thriving in these ambient conditions anyway.
I was just reinforcing the point - a little clumsily, granted - that what works one year may not work in another. And the rules and general advice you will read on how to care for tomatoes in a greenhouse are always likely to need modification year to year and place to place. More so than some other plants - chillies and cucumbers for example both seem less particular and the same treatment in a cool or a hot year seems to work well enough. You get more or less fruit, but the quality is far less affected than with tomatoes. In my experience, which is limited.
Gardening on the edge of Exmoor, in Devon
“It's still magic even if you know how it's done.”
Another problem with overwatering is keeping the roots permanently wet or even damp. There aren't many plants that enjoy wet feet. Tomatoes, especially, thrive on controlled neglect.
A wilting tomato plant doesn't necessarily need water. It depends when you observe the wilting. In the middle of a hot day, a plant will wilt. I wilt in the middle of a hot day. If you see the plant wilting, wait till the sun has gone down. If it's still wilting, water. If, as frequently happens, the foliage is back to normal, don't water.
Can you post a photo of foliage on the blight-riddled plants? "Blight" has become a generic term. Specifically, early or late blight could have transferred from the spuds but there are other fungal problems that, while they resemble those two blights, could be something else. There are even fungal problems that are almost exclusively GH-related.
Here you go, Ital...it started just after the spuds contracted Early Blight and spread over the 2 plants ( Moneymaker ) next to the louvre vent, the 2 Gardeners Delight plants further down the greenhouse, although infected, don't seem to be as bad.
On the foliage I stripped off a few months ago, you could clearly see the concentric circles indicative of Blight.
2 months further along and the leaves are now like this.
Maybe I'm wrong, because I was told by someone on another forum that in 30yrs of greenhouse tomato growing they had never had Blight, as the conditions were totally wrong for Blight to take hold.
Looks like early blight. It's about the most common fungal problem in the home garden.
The only way you'll keep any fungal disease out of a GH is to have it sealed. Open a door or window and you give the spores access. They're in the air, they travel on the breeze.
We have grown tomatoes in the greenhouse for 30 years, I don’t change the soil as such, just skim off the top layer, replace with some compost from a Tomorite grow bag and some garden compost. I’ve fed them twice I think, could be once. I think maybe the reason we’ve not had blight is that we are completely isolated, so I don’t suppose anyone grows anything for about 2 miles or so around us, I haven’t a clue who lives where or what the grow.
Gardening on the wild, windy west side of Dartmoor.
Isolation definitely helps. Nothing worse for a tomato grower than discovering a neighbour planting potatoes.
Good idea to change the top layer of soil too. Any nasties that have settled on the surface will have gone. Outdoors, I turn over the soil to the depth of the spade, burying any common nasties.
Italophile - toms don't like wet feet? I've been leaving my pots in a saucer with about a half inch of water so they don't die in this heat. I can't always get out to water twice a day.
Posts
I agree with most of the good advice on this thread, but I don't think this is correct.
Blight is typically caused by airborne fungal spores in wet conditions on the leaves.
Well directed watering at the base of the plants is not going to cause blight.
But if you keep watering and keep the soil surface damp by doing so, you raise the humidity locally and increase the risk of blight - given that a wet summer in itself makes blight more likely.
In this heat, even watering the surface has little impact, the water evaporates very quickly for one thing and the spores are not thriving in these ambient conditions anyway.
I was just reinforcing the point - a little clumsily, granted - that what works one year may not work in another. And the rules and general advice you will read on how to care for tomatoes in a greenhouse are always likely to need modification year to year and place to place. More so than some other plants - chillies and cucumbers for example both seem less particular and the same treatment in a cool or a hot year seems to work well enough. You get more or less fruit, but the quality is far less affected than with tomatoes. In my experience, which is limited.
“It's still magic even if you know how it's done.”
A wilting tomato plant doesn't necessarily need water. It depends when you observe the wilting. In the middle of a hot day, a plant will wilt. I wilt in the middle of a hot day. If you see the plant wilting, wait till the sun has gone down. If it's still wilting, water. If, as frequently happens, the foliage is back to normal, don't water.
I use Quadgrows like below, which give a constant, even watering and the reservoirs are full of healthy, white roots that are totally submerged.
I think the toms caught the Blight from the spuds that were close to the greenhouse.
On the foliage I stripped off a few months ago, you could clearly see the concentric circles indicative of Blight.
2 months further along and the leaves are now like this.
Maybe I'm wrong, because I was told by someone on another forum that in 30yrs of greenhouse tomato growing they had never had Blight, as the conditions were totally wrong for Blight to take hold.
The only way you'll keep any fungal disease out of a GH is to have it sealed. Open a door or window and you give the spores access. They're in the air, they travel on the breeze.
I think maybe the reason we’ve not had blight is that we are completely isolated, so I don’t suppose anyone grows anything for about 2 miles or so around us, I haven’t a clue who lives where or what the grow.
Good idea to change the top layer of soil too. Any nasties that have settled on the surface will have gone. Outdoors, I turn over the soil to the depth of the spade, burying any common nasties.