March Gardening Tips

Monthly Proven Tips and Solutions for Granite State Gardeners
Fresh cut on apple

Gradually rising spring temperatures slowly draw home invading insects out of hibernation.

There are five common home invading insects in New Hampshire, none of which will harm people, pets, furnishings, or buildings. Nuisance insects can be picked up by hand and tossed outside or flushed away, or sucked up with a vacuum cleaner. Insecticide treatments are not recommended because they work too slowly to control the problem and are toxic to humans. Prevent insects from getting inside your home next fall by removing air conditioners when they are no longer needed, and taking care to seal up cracks around windows and doors, particularly on the sunny southern and western sides of the house.

Disinfect plant containers that were used in the previous gardening season.

No matter what the containers are made of, disease harboring debris can build-up inside. To disinfect pots, soak them in a solution of one part bleach to nine parts water for ten minutes. You may need to use a scrub brush to clear away stubborn debris. Finish by rinsing pots with clear water and allowing them to dry before using them again. Filling disinfected pots with fresh, sterile potting mix will also help prevent insect and disease issues.

March is the time to start pruning woody plants.

Make sure your pruning tools are in good condition and remember to wait to prune spring blooming shrubs until after they are finished flowering. When in doubt, a good place to start is removing any branches that are dead, diseased, or damaged. Next, look for limbs that are crossing or rubbing. Aim to remove no more than 1/3 of the total living branches from a tree in a single year.

Late March is a good time to start some annuals and cold hardy vegetables, such as: heliotrope, viola, snapdragon, pansy, leek, onion, early greens, broccoli, cauliflower and kale.

Start seeds based on when you expect to be able to plant flowers and vegetables in your garden. Cold tolerant vegetables can often be planted 2 to 4 weeks before the last frost, while warm season crops and flowers should be planted after the last frost. For central New Hampshire, Memorial Day is a conservative estimate for the last frost date.

Avoid injuring lawns by limiting foot traffic as the snow melts.

Wet soils are more likely to become compacted when soil is wet. Compacted soils have a reduced ability to absorb water, making erosion and or polling or standing water more likely. Turf grasses also tear from the soil easily when the ground is thawing in the spring.

Ornamental grasses that were left standing in the winter should be pruned to within a few inches of the ground in early spring before new growth starts.

Any number of tools can be used to cut grasses, including hand pruners, hedge shears, saws, string trimmers and lawn mowers.

Look for viburnum leaf beetle (VLB) egg-infested twigs and destroy them.

Rows of 1-2 millimeter brownish-black bumps on the undersides of small twigs are the evidence of VLB egg laying. Infested twigs should be pruned out and burned or thrown away. Know that some viburnums are more susceptible to VLB than others. Arrowwood (Viburnum dentatum), European cranberrybush (V. opulus), American cranberrybush (V. opulus var. americana), and downy arrowwood (V. rafinesquianum) are especially attractive to the pest and frequently suffer considerable damage.


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Got questions? The Ask UNH Extension Infoline offers practical help finding answers for your home, yard, and garden questions. Call toll free at 1-877-398-4769, Monday to Friday, 9 a.m. to 2 p.m., or e-mail us at answers@unh.edu.