Northern & Central Midwest
Set up Cold Frames
Even if there's still snow on the ground, put cold frames over garden beds to start warming the soil. You can even sprinkle spinach and kale seeds on the snow and they will get a very early start. Use recycled windows, window well covers, or anything with a clear top as the covers for your cold frames.
Transplant Seedlings Early
If you've started seeds indoors, transplant the seedlings into individual pots when they produce two sets of true leaves. Increase the light and begin fertilizing with a weak fertilizer or fish emulsion solution. Keep fluorescent lights only a few inches away from the tops of the plants for stocky, healthy growth.
Start Garden Clean-up
Enjoy the periodic warm days by getting some of the spring tasks out of the way early. Gently remove dead foliage from around perennial crowns (no need to remove it entirely). Cut back to the ground all perennials and ornamental grasses that were left standing for winter interest.
Don't do Anything to Emerging Bulbs
Bulbs that begin to send up green shoots when the weather is prematurely warm will usually not be harmed by late frosts. There may be a bit of tip damage, but the flower buds are still protected beneath the soil and will bloom later just fine.
Prune on Warm Days
When you get the occasional warm day, get out and prune. However, be selective about which trees you prune. Avoid pruning trees whose sap runs freely in warm weather such as elms, maples, and birches. If pruned in spring they will "bleed" sap profusely. This won't harm the trees, but it is unsightly. Prune these trees when temperatures are very cold or wait until late June.