Cool-season crops such as carrots, lettuce, onions, beets and radishes can usually be planted in April. They should be planted after the danger of frost has passed, so gardeners in southern Michigan can usually plant earlier than those in the Upper Peninsula. You might also want to start the seeds of tomato or pepper plants in a seed starter kit during April.
A second planting of cool-season crops can be done in May so that harvest times will be staggered. You can also plant the seeds of pumpkins, watermelon, cucumbers or squash. Seedling plants of vegetables such as eggplant, pepper and tomato can be planted during this month as well.
Beans can be planted in the first week of June. You may want to make a new planting in the middle of the month and again near the end so there can be a longer harvest time. There will still be enough time left in the season for another planting of spinach, lettuce and radishes.