This time of year, it's so hard to resist the early seedlings at the hardware store. It will be at least a month until I can set out tomatoes (even in southern Virginia), without having to constantly cover and uncover them. Even the broccoli and spinach still need a little protection at night.
BUT - if you don't have a greenhouse, you can build a quick, inexpensive cold frame - the kind that keeps on giving.
All you need is at least 6 bales of straw (last time I checked Lowe's sold these for $4.29 a bale). (You can do it with 4, but very few plants will fit inside.) Add either a plastic tarp, or better yet 2 old windows, and you're set.
Arrange the bales (I used 6) in a rectangular pattern - 1 bale on each end, and 2 bales on each side. Turn them so they form a closed rectangle. (The photo shows a U-shape, with plants set in, just waiting for the end bale to close it up).
If you are using an old window,(or two), make sure the bales are close enough so the windows sit comfortably across the top. What you've just built is a miniature hot house - a straw box with a glass top.(I found 2 large glass patio doors on Freecycle for my cold frame.)
If you use a plastic tarp instead of windows, lay it across and weight it down with bricks/rocks/cinder blocks.
This bare-minimum cold frame will protect even your smallest seedlings until it's planting time.
When the temperature rises enough to plant, take the windows/tarp off for a couple days, and let the seedlings harden off to the open air.
The basic idea can be expanded on with a "flooring" of compost or dried manure, with the plants set in trays directly on top. The heat from the compost and manure will add extra heat even on the coldest days.
The cold frame size is limited only by the number of available windows, or the size of the tarp available.
After all your seedlings are planted, the bales can be re-used as planters (try planting tomatoes or potatoes directly into the straw bales if you're short on ground space -hollow out a little pocket, add your seedling and dirt, and water regularly), or they can be broken down and spread on the garden as a mulch that really holds the moisture in.
Mom to an 20-yr-old. After 10 years of homeschool/unschooling adventure she's now working her magic in college. Following a 15 year stint in the corporate sales world, I've spent the last 11 years as an online bookseller with my pup Chewy (Chewybooks on Amazon, Chewyboo on ebay), previous to that I managed a bachelors degree from a radical college, built a small greenhouse 2 years ago and 500 gallon rain barrel system last year.