Sowing Flower Seeds and Other March Gardening Tips
Leonard Perry, UVM Extension Horticulturist
and Charlie Nardozzi, Horticulturist
Sowing seeds of some flowers and vegetables, pruning, and checking perennials for soil heaving are some of the gardening activities for this month.
Sow slow-growing flowers such as pansies, begonias, and vinca early in the month. Sow verbena, petunias, geranium, and impatiens later in the month. But wait until April to sow seeds for tomatoes, peppers, eggplants, and most flower varieties that cannot be transplanted until the danger of frost is past. Cabbage, broccoli, and other cole crops that can be set out in early spring all can be started this month. Check on the seed packet to see if seeds can be started indoors, or should be sown directly in the ground when the weather warms up.
Ideal growing conditions for starting plants from seeds include temperatures of 70 degrees (F) for germination, then 60 to 70 degrees for good seedling growth. A seedling heat mat under the flats helps to maintain a proper temperature.
To keep seedlings from getting spindly, use high light intensity, as in a south-facing sunny window. Even there, rotate seed flats every couple of days so they don’t grow sideways toward the light (i.e. “phototropism”). For even light, many use a seed germination light stand you can buy from garden stores or online. Or you can use shop lights, with balanced spectrum tubes (cool white work fine too), hung six to eight inches above the seedlings. Newer slimmer tubes (such as T8) are more efficient. Hang them on chains so you can move them up as seedlings grow. Use a timer (as found in hardware stores) to keep lights on 14 to 16 hours a day.
March is the perfect time to prune fruit trees, most ornamental trees, and summer-flowering shrubs. Wait to prune spring-flowering shrubs until right after bloom, or you’ll cut off their flower buds for this year. Wait to prune maples and birches until after they leaf out, otherwise their rising sap will run or “bleed” from open wounds.
Sharpen pruners if they are dull, using a sharpening file from hardware stores or online. Remember the 2 C’s and 3 D’s—remove any crossed and crowded branches. Thinning opens up a tree canopy for more air and sunlight, which gives better growth and less disease. Also remove any dead, diseased, or damaged branches. Cut broken branches back to a main branch or the trunk rather than leaving stubs. Wound sealer isn’t necessary, as it may seal in moisture and bacteria which lead to rots.
Take a walk around your yard to check for perennials that may have heaved out of the ground, exposing their roots to drying winds. Gently tamp them back into the soil or, if the soil is too frozen, surround them with mulch as protection, tamping down later.
If you potted some bulbs last fall, and they’ve been in a cool space over winter, bring them into warmth now to “force” into bloom. Or simply buy some potted or cut tulips and daffodils to bring spring indoors early. There are many other flowering potted plants to choose from during the Easter season including, in addition to the Easter lily, primroses, azaleas, cineraria, and more. Shamrock plants are available for St. Patrick’s Day. These members of the Oxalis family are easy to grow, and prefer a sunny location with even watering.
Other garden activities for this month include attending flower shows and garden lectures, visiting a maple sugar house, and cleaning existing (or adding new) bluebird houses.
Charlie Nardozzi is a nationally known horticulturist, author, gardening consultant, and garden coach (CharlieNardozzi.com). Distribution of this release is made possible by New England Grows– a conference providing education for industry professionals and support for Extension’s outreach efforts in horticulture.