Other vegetables like spinach don't mind if it gets a little too wet once in a while. It stays on throughout the cool season serving the dual purpose of pest protection. Notably, leaf miners which otherwise can be a serious problem in spinach can't lay a finger on a single leaf. In addition to the posts I usually throw some dirt on the edges to make sure it is completely bug-tight. When laying out the row cover be sure to leave it loose enough to allow the plants to grow unimpeded.
Indoor seedlings thrive.
There are several ways to keep seed-starting soil warm for germination. The simplest is to find a warm location in the house such as on top of the refrigerator. Planting flats sit on top of sheets of metal siding warmed by a 60 watt light bulb a few inches below. By moving the bulb up and down, I can control soil temperature from the low 50's to the mid 70's. This is a relatively inexpensive solution.