There is a lot going on in the garden this month. The weather tends to remain chilly, so cool-season vegetables still thrive. The days are also lengthening, which makes it a good time to start some warm-season crops.
If you can't find warm-season vegetable plants in the nursery yet, start them from seed.
Planting flower seed now widens the selection of flowers you can grow and ensures that you'll get blooms in spring and summer.