Planting:
April is prime-time for planting all sorts of edibles, and also for continued clean-up and preparation. Start Brussels sprouts, cauliflower, cabbage, and broccoli. Sow another set (or your first set) of beans, squash and sweet corns, carrots, summer squash turnips, sweet peas and leaf lettuce. Sow spinach seeds so that you can have sweet leaves before the weather starts to warm up and make things bitter. You can also sow escarole and endive for a fall harvest.
Garden maintenance:
Dig compost into your soil, and mulch around your existing plants to help suppress weeds and retain water and heat. Use organic fertilizers to encourage growth without compromising insect well-being. Don't mulch around herbs, and check crops like brassicas (cabbage, kale, broccoli) for signs of cabbage worms. You can make sure there are no whiteflies around any tomatoes that you might have transplanted.
Harvesting:
If you were ahead of the game, you might already be harvesting leaf lettuce and some carrots. Parsley (especially if it survived the winter like ours did) will be full of fresh leaves and a delicious flavor. Pick snow peas while they are flat, and don't forget that the tendrils can be used in cooking just like the pods!