The weather in recent days should be a timely reminder of the challenges of early-season gardening in this part of the world. Although the forecast calls for temperatures in the 60s this week, let’s not forget that we were scraping ice off our windshields Saturday.

We’re still a little more than five weeks away from the average date of the last killing frost and, if weather patterns stay true to form, the interim will be the windiest time of the year. That’s not to say that we can’t begin planting the first vegetables of the season once the ground dries out. What it does mean is that most early gardeners will be growing their vegetables underground.

The most reliable March plantings come from root crops: radishes, carrots, turnips, onions and potatoes. Wind doesn’t bother them, and once the soil is warm enough to work, cold will no longer be a problem.

Radishes, carrots and turnips are grown from seed. Once the ground temperature reaches 40 degrees, carrot and turnip seed will germinate.

Radishes, which are a fast-growing, cold-hardy little vegetable, act like they have no internal thermometer and will sprout at the first hint of spring.

A number of years ago I learned an easy way to raise the soil temperature to germinate seeds for root crops, which allows for early planting, even when the temperature is fluctuating between daytime highs in the 60s and overnight lows in the 30s.

Seeded root crops are most efficiently planted in rows spaced at least 1 1/2 feet apart. The success of these crops will depend on good soil preparation. The dirt should be tilled to a depth of at least 6 inches. If you have a high clay content in the soil, it may be worth the effort to go a few inches deeper and even add sand.

In the case of carrots, gardeners with dense soil should steer clear of the longer Imperator varieties, which can grow to 9 inches. Danvers and Chantenay carrots, both of which are thicker at the top, and Nantes varieties, which are short and of uniform thickness, are better suited for heavier dirt.

Once you’ve tilled, draw wide furrows, 2 inches deep and 2 inches wide, in the soil, and water the furrow by filling it with water and letting it sink it. Sprinkle your seeds in a thin line along the inside of the furrow.

When working with small seeds, it’s difficult to drop them one-by-one in a neat row, but you don’t want them landing on top of each other. You will have to thin them later, and you don’t want to disturb the seedlings that you keep.

Cover the seeds with about 1/4 inch of loose soil, just enough to hide them from direct sunlight.

Next, roll out kitchen plastic wrap over the top of the furrow and secure it at the ends and along the sides with rocks or bricks. Covering the edges with dirt isn’t good enough; the wind will blow it loose and you’ll find the plastic wrap flapping in a tree.

The plastic wrap will trap heat and moisture in the soil and speed germination. In fact, after an hour in the spring sun, the underside of the plastic wrap will fog up and produce precipitation to keep the dirt around your seeds moist. I have been astonished at the difference it makes.

You can’t use the plastic wrap in warmer weather, when daytime temperatures hit 70 degrees and stay there, because it will keep your seeds too warm and they will rot. And once your seeds germinate and the shoots are more than an inch high and ready to be thinned, the plastic wrap must go. Leave the furrow in place to protect the seedlings from wind and take care to water gently until the roots take hold.

Carrots and turnips should be thinned to 3 inches apart, radishes to 1-2 inches, depending on the variety. Successive plantings of seeds three weeks apart will extend your harvest. Most varieties of radishes will be ready in about three weeks; carrots and turnips will start to mature in June.

Next week: Planting potatoes and onions.

 When she’s not writing about foods and gardening, Gwyn Mellinger is teaching journalism at Baker University. Her phone number is (785) 594-4554.