So I say to you, think differently about planting your garden. You needn't rush into a full planting on May Day because we have a long, long growing season. You don't need to plant a whole row of broccoli - you can plant two every other week or so. You can engage in succession planting to insure a continuous harvest of good food from February through December.
There are a variety of tomatoes, for example, that produce very early, mid-season, and very late. An early planting of a hardy determinate in a large container in a protected area means you might start getting tomatoes in June. The large heirlooms like Brandywine take longer and can be planted later for a crop in September and October. And there are many plants that will ripen easily between those months. If you plant carefully, you have have home grown tomatoes six months of the year and longer if you have a small greenhouse, cold frame, or lean-to. The same can be said of cucumbers, squash, eggplant, peppers, onions, salad greens, peas and beans.
Herbs are incredibly hardy and can be planted out most any time. Many are perennial and one or two healthy plants will provide you with ample oregano, thyme, rosemary, chives, sage and marjoram.
Those of us in the seedling business what to provide you with pants that are ready for transplanting into your garden or container at the appropriate time. We have experimented in our own gardens and had successes and failures that we are happy to share. I have planted many a tomato plant in March. Some have thrived and blessed me with early harvests but some have succumbed to horrid diseases caused by cold winds and saturated soils with a hailstorm or two thrown in for good measure. If you are unsure about your soil, garden location with regard to drainage, wind and sunlight hours - start with the hardiest plants like kale and broccoli. Invest in a soil thermometer and bring out your tomatoes when you soil is at a consistent 55 degrees and cucumber seedlings when the temperature rises to 60 degrees. Talk to your neighbors and others who garden in your area - they will be more than happy to share their experiences. But nothing beats your own. Remember - you don't really want to have the biggest zucchini on the block. You want to have the best zucchini on the block.