University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article

Charlie Nardozzi, Horticulturist and
Leonard Perry, UVM Extension Horticulturist
Pruning back ornamental grasses, getting patio containers ready for planting, and starting dahlias indoors are some of the gardening activities for this month.

If you left your ornamental grasses intact last fall for their fall and winter effect, and for seeds for birds, you can go ahead and prune them back to a height of about 6 to 12 inches. If you remove the old growth before new growth starts, and don’t cut back too close to the ground, you won't risk damaging new sprouts when they emerge with warm weather later in spring.  Add prunings to the compost pile, but the thick stems of some grasses should be shredded or cut up first so they’ll decompose more quickly.

When planting large containers for the deck or patio, save on soil by creating a false bottom. Most of the plants you'll use don't need more than about a foot of soil depth for their roots, so put some empty plastic soda or water bottles in the very bottom, then cover with landscape fabric or a piece of cardboard cut to fit to keep the soil from eroding. Plastic pots turned upside down also work, as do coarse and inexpensive wood shavings.  Some use those Styrofoam packing “peanuts” (put in plastic bags so they’re easily handled and contained).
To control annual weeds in the lawn, spread corn gluten meal with your lawn spreader when forsythia are blooming. That's when many weed seeds, such as crabgrass, are germinating. It's a safe, organic option for preventing the germination of weeds, and it provides a small dose (maybe 9 percent) of nitrogen fertilizer. The best controls for weeds, however, remain a good soil conducive to growing grass, and proper lawn culture.
While safe and environmentally friendly, corn gluten products can be expensive with such a demand now for corn-derived products from corn syrup to ethanol.  A 20 to 25 pound bag, depending on product, may treat 1000 square feet of lawn or beds, and cost around $30.  This means to treat a quarter acre lawn, you may need to spend $300 or so.  Like all “pre-emergent” weed killers, corn gluten will keep seeds from germinating.  So make sure any desirable flowers or vegetables have germinated, and have “true” leaves, before applying around them.
Get flowers sooner on dahlias by potting up tubers and growing them indoors until it's warm enough to plant them outside. Pinch the growing tips when they get 6 inches tall to keep the growth short and stocky for easier transplanting into the garden.  Keep them in a cool place, such as garage, so they don’t grow too fast. 
To get a head-start on fresh greens, sow seeds in a large, shallow container. Keep the container outside during the day and bring it in at night if the temperatures dip below freezing, or protect it in a cold frame. A window box with colorful greens is not only ornamental, but makes for easy picking and protection from hungry rabbits.
Woody perennials differ in the way they should be cut back in spring. If butterfly bush has died to the ground, cut the dead stems to the ground. Otherwise just shorten them by about one third. Cut back Russian sage, rue, and artemisias to about 8 to 12 inches from the ground. Don't prune lavender until new growth appears, and then just shorten the stems by about one-third. Heather should be lightly pruned to remove the old flowers and the tips of the shoots, but don't cut back to brown wood, stay in the green.  Wait until rose shoots and leaves emerge to prune, in order to know what stems died and which are living.

(Charlie Nardozzi is a nationally known horticulturist, author, gardening consultant, and garden coach; 

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