Although the nights and soil are still cool in your garden, there are some great vegetables that you can get started with. Once established, young kale, spinach and onions enjoy the cool spring weather and with just a little bit of protection you harvest nutritious home grown vegetables earlier.
The start of the gardening season revolves around when the last frost occurs. The average date for this is easily found on the web, but also from your local extension office. The important thing to remember though is that the number is an average, so some years that last frost will occur 2 to 3 weeks before that important date. Those last few frosts are generally very light so getting a head start on your garden by being ready to protect your crops if needed is worthwhile.
Cool weather crops such as peas, cabbages and salad greens can be put into the ground early if you warm the soil just a little and provide some protection. About 8 weeks before the frost date, if the weather looks promising, increase the soil temperature by laying a plastic sheet over the area. The sheet stops any cold rains from cooling the soil, and increases top layer of soil so that in just a few weeks you can plant your spring vegetables. If the temperatures fall for a while, protect the vegetables with row covers or, for individual plants, use a "Wall O' Water" cloche to maximize the warmth around the plant and give it a good start.
Warming the soil also lets you can also take a chance and plant a few of the warm weather crops up to two weeks early if the weather looks good. Do not plant a full row, but if you do not have a frost you will harvest your first beans two weeks earlier than your fellow gardeners who waited. If a late frost does occur you are no further behind than those who waited.
For those with a cold frame, the garden year can start even earlier. Place the cold frame directly on soil and add a layer of compost. The heavy plastic of the cold frame captures early season sun and warms the soil efficiently. Plant cool weather salad greens and colorful chard directly into the cold frame and let the seedlings grow in the warm environment. Remember to lift the lid of the frame when the sun is out as the solar heating even in winter can burn the plants inside in just a few hours.