As I go through some gardening videos and books, I realize the importance of stocking up on a few soil thermometers. These can help us maintain soil temperature around an optimal 70 degrees-F (21 C). We can raise or lower this temperature through various mulching techniques. The video How to Grow Cool-Weather Vegetables (1986, Kartes Video Communications) makes a very important point: Soil temperature is much more important than air temperature. So if some of us choose a soil-based growing method in addition to hydroponics, we can start thinking now about protective coverings that will keep soil warm, thus increasing the productivity of our plants. Those coverings will include plastic canopies over the garden beds, as well as plastic mulch directly over the soil. One more important point from this video: By adding four to six weeks of growing time on both ends of the season with proper covering techniques and by effectively applying the succession-planting method, we reduce the need to store as much food.
Offered by Mike.
This is true in most cases that soil temperature is more important than air temperature. But some transplants will not survive not matter how warm the soil is, if the air is too cold. Regarding plastic canopies over garden beds, where are you going to get this plastic? And when all your pre-stocked plastic is torn to shreds, then what? Plastic is not an option. Also, your beds should/would already be covered by the dome to facilitate providing light for the plants. The prediction is no sun for 15+ years for most people! Heating the soil by coverings is irrelevant as within the domes we have direct control over the "seasons."
Offered by Roger.