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.
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?
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.