If your goal is to keep the rooting area at 70 deg, then 70 deg irrigation water would work. The attached link recommends not exceeding 80-85 deg water temperature. Here is a link that might be useful: irrigation of greenhouse vegetables

Yes. I've been growing vegetables year 'round here for the last 10 years or so. "Non-tropical" vegetables can take light frosts. There is a large list of them. Almost all root vegetables, however these must be started off in warm soil. I sow them in early September. Cole Crops - brassicas of all kinds, many Asian vegetables -pretty much anything related to cabbage or mustard. Cauliflower is a pain here. swiss chard, and many lettuces and other greens withstand frosts. I just planted lettuces today at church from transplant. I am no longer planting anything from seed. Seeds need about 70 degrees, in general to germinate. Tenting them can help. Row covers work unless it is freezing rain. I use old sheets for row covers in my raised beds, and I usually use plastic on days like today, to heat up the soil a bit and get better growth. I never ever let the plastic touch the vegetables because that burns them when it freezes. I keep frozen wet out of the vegetables, that kills most back to the ground and they don't aways recover. I protect spinach and lettuces. There are a variety of ways to do that. I protect only when there is going to be a hard frost, artichokes, and celery. I use old tree pots for this, or heavy cardboard boxes (not in rain) with a rock or brick on them. You can use heat sinks if we get a 2 week freezing period like we sometimes do. I like bricks the best for this. I just plop them inside the tented veggies. I make tent frames out of PVC and use them every year. My favorite covers for the garden are old shower curtain liners. Heavy plastic! You can also build units around existing beds using bales and plastic held with bricks . I have done this. The most important thing when tenting or protecting is getting in the light and ventilation. You can't let the heat build up for any length of time (under a tent it can easily get 20 degrees warmer than outside, if it's sunny)...so you have to be present to tend the vegetables. GGG

That's why we try to get them into the ground as soon as we can...when they are ready to grow, they're gonna grow and it is important to get them into the ground before they get rootbound. Once they reach a certain point with a certain number of leaves, growth just explodes....as you can see with your root growth just this week. To a certain extent you can slow down plant growth by keeping the plants at a slightly cooler temperature. People often grow their seedlings at too high of an indoor temperature and get very rapid growth. While it seems cool at the time, it isn't necessarily a good thing. Plants that grow too fast indoors can get rootbound and stall. I have tried to keep mine from getting too tall too fast by moving them out to the greenhouse when they were tiny and had only 2 true leaves. It worked up to a point....but once the daytime highs were in the 70s, their growth accelerated even though the nights in the greenhouse usually were in the 40s or low 50s. Inside the house I try to keep them at 60-65 degrees and no warmer, which usually means closing off the heating vent in the room where the light shelf is because that many lights make enough heat on their own. Sometimes I even close off that room from the rest of the house and open windows to let some cool outdoors air come in to cool down the room. I'll link the soil temperatures below. You should go by the 3-day average, but it will seem low because it is reflecting the cold days/nights we just had. You could look at the 1-day and see what a difference a warm day and night makes. With the nice weather we're having now, the 3-day averages will climb pretty fast, at least until next week's cold front rolls through. Dawn Here is a link that might be useful: 3-Day Ave Soil Temps At 4

Almost everything I planted less than two weeks ago has come up - green beans, cucumber, beets, radish, lettuce, kale, spinach, carrots, bok choy. And the two volunteer tomatoes (from last year's dropped fruit) are doing well transplanted into the garden. This rain has really helped get those seeds germinated. And the cocoa shells are really helping too I think. The raccoons and cats have avoided the beds since I put it down. Also the rain has brought up my wildflowers - mostly clarkia and poppies - which are tall and starting to bloom. On the other hand, that storm last week pulled down a Ceanothus I planted a year and a half ago - which is now 10-12 feet tall - it was 18" a year ago. But I've got it staked now and hopefully it will make it.