Leave the Mulch
Warm days may tempt you into removing winter mulch but wait a bit longer. We still could have snow and cold temps, and plants still need protection. The freeze and thaw cycle of early spring can damage plants that have survived a cold winter.
To get an early harvest of lettuce and other greens, dig out a large shallow container and sow some seeds. Grow them indoors until the weather warms enough to put them outside during the day. Keep cutting leaves from the outside of the plants to prolong the harvest. Or you can sow seeds for a mesclun mix and cut off the leaves when still young. They will regrow for another harvest in a few weeks.
Pot Up Summer Bulbs
Dahlias, cannas, and glads are available now and you can get a head start by potting them up indoors. Plant them in large containers and keep them in a cool room, if possible, in a sunny window until planting time outside. Dahlias may need to be pinched back while still indoors to keep the plants from getting leggy. You'll get earlier blooms with this technique.
Spray Dormant Oil
Spray horticultural oil on fruit trees, such as apples, plums, and cherries, to smother any overwintering insects. Choose a calm day when temperatures are above 40 degrees F, and be sure to cover all sides of the branches. You can also apply it to evergreens to control spider mites and other insects. Carefully follow the instructions on the label for proper usage and appropriate plants.
Get the Cold Frame Ready
Cold frames are handy for hardening off seedlings. You can make a simple cold frame by placing hay bales along the perimeter of a rectangle, and placing old windows or a glass storm door over the top. Purchased cold frames are convenient -- some have thermostatically controlled tops that open automatically when the temperature inside hits a designated point. Since the midday sun can heat things up quickly, this feature is especially handy if you're away for long stretches during the day.