University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article


By Dr. Leonard Perry, Extension Professor

Dr. Vern Grubinger, Extension Associate Professor
University of Vermont

Hopefully, by May, you have done all your PLANNING for the garden because this is the month to PLANT, even in the coldest parts of Vermont. Are you ready?

Planting starts with preparation of the soil, including a soil test to determine the soil's pH or acidity level and its available nutrient level. Most vegetables and flowers prefer a soil pH of 6 to 7 and plenty of calcium and magnesium. Adding lime is the way to correct the pH of acid soils, and it's a good means of adding calcium to the soil. If your soil is low in magnesium, applying a "high-mag" limestone can solve that problem, too.

Your crops also need high levels of phosphate and potash to perform well. A soil test will provide you with fertilizer recommendations for these nutrients which, like lime, should be mixed into the soil prior to planting. You can obtain a soil testing kit from any University of Vermont (UVM) Extension office; the Agricultural and Environmental testing Laboratory, Hills Building, UVM; and many feed and garden stores. The cost is $10, payable when you send in the sample. In addition to nutrient recommendations, the lab will send you information on organic fertilizers, if requested.

To prepare your garden for planting, you will need to rototill the soil to a depth of eight to ten inches to work in the recommended lime and fertilizers as well as compost or well-rotted manure. That also will incorporate any leftover plant residues from last season. Break up clumps to help aerate the soil.

However, if you are not adding fertilizers, and your soil has good tilth from previous years of compost or manure additions, you can skip the rototilling. Instead, just use a shovel to loosen the soil in the rows before planting. This will avoid the damage to the soil structure that frequent rototilling can cause.

If you are going to lay black plastic to control weeds and warm the soil, it's important to remove sticks and stones, then rake a very smooth seedbed. If the surface is lumpy and uneven under the plastic, it will not warm the soil as well as when there's a nice tight fit.

If you have soil that contains a lot of clay, raised beds may be the answer to warm up the soil faster and drain excess water away from plant roots, thus reducing the likelihood of soil-borne diseases. Use a rake, shovel, or a furrower on a garden tiller to gather soil into ridges. Flatten out the ridges with a rake to form beds that are at least four to six inches high and as wide as the crop growth habit will require. Be sure to allow enough room between beds for easy planting and harvesting, and for weed control during the season with your rototiller.

Of course, before rototilling or spading your garden, you should make sure the soil has dried out enough because working wet soil will harm the soil structure by causing compaction. Test by squeezing a handful of soil. If it forms a ball, the soil is too wet to be tilled. If it crumbles, then it's okay to till and plant.

How do you decide what to plant where? While a lot may depend on personal preference, there are a few things to keep in mind. Unless this is your first year having a garden in this spot, it's important to rotate your plantings. This means not planting the same family of crops where you planted them last year. This practice aids in the control of diseases and insects and varies the fertility demands on the soil.

You also need to take into account the mature size of your plants. Unless shading is desired, be sure to plant tall plants like sunflowers or corn where they will not shade out lower growing plants. And leave plenty of room for sprawling crops like winter squash. In small gardens, some vine crops like cucumbers can be trained to grow up onto wire fencing, thus saving space.

When to plant is another important consideration, unless you will be diligent about using frost protection, such as floating row covers or paper or cardboard caps. As a rule, in early May you can plant lettuce, spinach, peas, beans, root crops (carrots, turnips, beets, onions), cole crops (Brussels sprouts, cabbage, broccoli, cauliflower), early sweet corn, and some flowers such as gladiolus. Although potatoes can be planted now, delaying planting may ward off disease problems like rhizoctonia (the dirt that won't wash off), which is common in cold, wet soils.

Summer flowering bulbs, including tuberous begonias and cannas can be planted in mid-May. Choose a well-drained and partially shaded area. Set the tubers in the ground so they are barely covered, placing them 18 to 24 inches apart to allow plenty of space for growth and air circulation. Fertilize and water when the soil is dry, preferably in the morning or early afternoon to give the foliage time to dry before nightfall to reduce chance of disease.

Wait until Memorial Day or later to put in warm-season transplants (peppers, eggplants, tomatoes), marigolds, and zinnias or to sow squash, cucumbers, and other seeds that require warm soil to germinate.

Other activities for May: buy flowers for your mother on her day; set up a drip irrigation system for the hot gardening months to come; divide crowded perennials; put up hummingbird feeders in early May.

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