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Do tomatoes need humidity???

 
Matthew Steffen
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1st off i live in Northwestern Montana and we are VERY dry here. I grow tomatoes and peppers in a hoop house. It gets VERY dry in there in the summer time and when i water every few days it will get humid. I am working on building an irrigation system to irrigate at the roots to build a strong root system as well as help with weeding and wonder if it do this will it be too dry for the maters or do i have nothing to worry about? Any help would be appreciated............
 
Alder Burns
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Location: northern California
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I think they will be fine with irrigation at the roots. Many thousands of acres of tomatoes are grown here in the Central Valley of CA, where summers are completely dry and no rain and temps regularly 100 plus. In a greenhouse setting you might need to beware of spider mites though...which always for me seem to be a problem with plants indoors or in a greenhouse, and seem to go away when they are moved outside into fresh air.
 
Adam Klaus
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Location: 6200' westen slope of colorado, zone 6
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I grow tomatoes and peppers in a greenhouse in Western Colorado, a climate generally similar to yours. My experience is that tomatoes actually prefer very low humidity, and like their foliage to remain dry at all times. Peppers, on the other hand, seem to love humidity, and also like to have their leaves watered regularly.

Tomatoes have a very broad and shallow root system, so IME they like to have the ground all around them moistened, not just a small area from drip emitters. This is less the case with peppers, which seem to have more limited root spread. Once the soil is completely warmed up, both tomatoes and peppers benefit from a moisture conserving mulch. You dont want to mulch too early, as it will keep your soil cool and these plants both need very warm soil to grow healthily. But evenly moist soil, like in a forest, is their preference. Both tomatoes and peppers do better with too little water than too much, likely due to their subtropical heritage. Mulch lets you water less, and also limits losses from blossom end rot, a major problem.

Another thing with tomatoes and peppers in a greenhouse, is that they do not like large differences between the daytime and nighttime temperatures. In commercial growing, this is known as 'diff'. Managing the greenhouse to have a low diff is not easy with our warm sunny days and cool nights. Anything you can do to minimize the temperature spread from day to night will make you plants grow better. In my experience, this goes as far as it being better to have a cooler daytime temp if you are going to have a cold night.

Peppers are much more sensitive to cold when young, I would say anything under 45 degrees at night will stunt the plants without killing them. Tomatoes are much hardier to cold when young, but still any temps down into the 30's will have a long term negative impact on the plants. In the fall, however, I find the opposite to be true. Mature pepper plants keep maturing fruit well even as the temperatures cool off in the fall. Tomatoes do too, but their rate of maturity seems to really slow down. Peppers seem to get the message that fall is coming and they need to ripen their fruit before frost.
 
Matthew Steffen
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I hate to make changes when things are working but i am sich of weeding. Got over 1,000# of maters and peppers out of the 14 x 20 last year...............
 
Adam Klaus
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In defense of the weeds, they are a really good thing for the health of the soil in your greenhouse. Over time, the soil in the greenhouse will really begin to suffer from loss of humus and buildup of unwanted nutrients. The first few seasons are easy, then things start to get weird. Having lots of weeds helps to keep all this in balance, so in many ways, you might be a bit more worried some day when you DONT have a lot of weeds! About year five, when i finally didnt have weeds growing rampant everywhere, productivity took a nose dive. Since then, I have soil tested and grown cover crops and ammended carefully, and now I have a nice balance of weeds once again. Without the weeds, the soil bakes, the earthworms perish, and soil health suffers. Balance is the key. Greenhouses are unnatural environments, so maintaining that balance is all the more difficult.
 
Matthew Steffen
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Adam Klaus wrote:In defense of the weeds, they are a really good thing for the health of the soil in your greenhouse. Over time, the soil in the greenhouse will really begin to suffer from loss of humus and buildup of unwanted nutrients. The first few seasons are easy, then things start to get weird. Having lots of weeds helps to keep all this in balance, so in many ways, you might be a bit more worried some day when you DONT have a lot of weeds! About year five, when i finally didnt have weeds growing rampant everywhere, productivity took a nose dive. Since then, I have soil tested and grown cover crops and ammended carefully, and now I have a nice balance of weeds once again. Without the weeds, the soil bakes, the earthworms perish, and soil health suffers. Balance is the key. Greenhouses are unnatural environments, so maintaining that balance is all the more difficult.


I add compost and cow manure both of which i have an unlimited supply of so i would think this would negate any negative affects of the weeds taking over?
 
Adam Klaus
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The thing I have found, myself also using large amounts of cow manure and compost, is that the chemical composition of these fertilizers is different from the chemical composition of the tomatoes you are growing. So over time, the levels of potassium, sodium, etc. in the soil will build to unhealthfully high levels. Soil fertility is about balance of nutrients, so when one nutrient gets too high, it causes other nutrients to become unavailable. The way that weeds help is that they are taking up different nutrients to your tomato plants, helping to keep the soil more balanced. In your situtation, over time, I might guess that you will have issues with inadequate calcium, phosphorous, and sulfur. Myself, I went too far trying to address the phosphorous deficiency, ended up over supplementing with rock phosphate, and that created issues with inadequate soil iron, a relatively rare situation in my area.
I hope that isnt more info than you wanted, or too confusing. Just trying to explain how nutrient balance in the soil is the key long term, and that lots and lots of weeds actually helps to maintain that balance.
 
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