6/14/08: It’s an issue of timing: the big things going to seed need time to do so (leeks, left; beets, right; parsley, rear right) and the little things need time to get big.
I spend a little more than a usual amount of my worry-energy worrying about the soil in the greenhouse.
Without the cleansing benefit of fresh rain and direct sunlight, the soil in the beds will eventually need to be replaced. Hopefully, I will not have to do this for another couple of years, but yes indeed I do still worry about it. I water from the hose and I can definitely tell that the top layer of soil is getting mineral stains: either the water itself, which is pretty “heavy” with iron and calcium, is leaving this stain or the soil itself is leaching it out. Either way, it will eventually affect the soil fertility, and it is something I need to keep an eye on.
A partial answer to this would be to gather rainwater to water the beds. I do this, on a hackneyed basis; in winter and early spring, melted snow or fresh rainwater are the only way the garden gets watered. The heat of summer means I need a lot more water. Until we get a load of rainbarrels lined up and connected, the hose is the way to go.
Another partial answer would be to mulch as intensively as I do outside in the main gardens to conserve that water. Let’s just say I am afraid to do that. We have slugs and sowbugs aplenty in the greenhouse: they do lots of damage to new growing things, so I really do not want to encourage them further by making their lives any more cushy than they already are.
Big tomatoes (rear), slug-eaten Cranberry bean seedlings, and a handful of clover seed
So here’s my partial answer today to the fertility/soil quality question. I underplant the tomatoes with beans, and then underplant the beans with a sowing of white clover. The clover and the beans are both nitrogen-fixing legumes: nodules on their roots make nitrogen, a plentiful airborne element, readily available to the soil, especially after the plant dies. (Green manures generally are in the bean family for this reason: the other things I use (oats, rye) are used for their sheer mass of greenery that the heavy clay soil needs.) It becomes a matter of timing, then, for what I do in the greenhouse in spring/summer: tomato plants first (planted into their permanent places at the beginning of May), beans planted in early June, and now once the beans are tall, the clover. The beans will get harvested and the tomatoes will get harvested and pulled out and then I will till under the clover and bean plants, add more compost and grass clippings, and then plant out everything for the fall/winter.
Right now the peppers and eggplants are not tall enough to be undersown with clover. Bean plants are too tall to underplant with these two.
Oh, and reason #859 why I love this greenhouse? It’s shaving a month off of the first tomato harvest! The early and determinate plants of Bellstar Paste are just loaded with fruit right now. Great for instant gratification gardening, I will admit.