Nancy E. Adams

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Q: New Hampshire towns often impose water bans during the summer months. Any suggestions on how I might conserve water yet still provide adequate moisture for my garden plants?  —Patricia Brooks in Nashua, N.H.

A cistern is used to store water collected from this Barrington Court Garden, England, rooftop. Updated models are made from recycled plastic drums or barrels attached to drip irrigation systems.

Water is as essential for a plant’s existence as it is for a human’s. While approximately 60 percent of the human body is comprised of water (by weight), 75–95 percent of the weight of some plants is due to this precious commodity. Established trees and shrubs seldom need additional moisture beyond that provided by Mother Nature. The trouble begins when tender annuals and perennials are subjected to extended periods of dry, hot summer weather—their relatively shallow root systems must be provided with supplemental water in order to survive and thrive.

Here are some water conservation techniques that may help your plants through this summer’s growing season.

• Select self-watering containers. There have been major advances in the mechanics and aesthetics of self-watering window boxes and decorative planters. The units come equipped with wicks and a water reservoir that keeps the soil evenly moist. Gardener’s Supply Company in Vermont (http://www.gardeners.com) carries a wide assortment of self-watering container styles and sizes.

• Utilize drip irrigation. A great deal of water is lost through evaporation, runoff and non-target penetration when overhead sprinklers are used. Instead, place drip irrigation systems throughout your perennial and annual beds. Water will slowly ooze/drip onto the soil exactly where the plants need it. Water infrequently but deeply so that the upper five to six inches of soil becomes thoroughly saturated. If overhead irrigation is necessary, water in the early morning hours.

• Apply organic matter to garden soil. Increasing the organic matter level in the soil will help it retain moisture, which can be particularly valuable for sandy garden soils. Incorporate one to two inches of mature compost each year into your garden soil for optimum results.

• Apply one to two inches of mulch. Mulches trap moisture as it evaporates from the soil surface. Pine needles, straw, salt marsh hay and ground leaves are just some of the commonly available mulch materials.

• Collect rainwater. Connect your gutter’s downspouts to a water-holding reservoir/cistern so that runoff can be collected from your home’s roof for later use. A one-inch storm produces more than 500 gallons of water on a 1,000 square foot roof!

Q: What is the latest word on controlling Japanese beetles? It seems this pest is a real nuisance for me and my neighbors.  —Chalmers Congdon in Hamilton, Mass.

Japanese beetles were first discovered in the United States in 1916 on New Jersey nursery stock. Although it was quickly recognized as a potential agricultural threat, eradication efforts failed to curb its spread and as the saying goes, the rest is history. Today, the beetle is found in all states east of the Mississippi and continues to spread westward at a rate of five to ten miles per year.

Insect damage falls into two categories. The first is due to chewing by the adult beetles. The adults emerge from the soil in June and July, and quickly begin to feed on such favorites as raspberries, roses, grapes and basil. They defoliate the plants by selectively eating the tender tissue between the leaf veins—leaving behind a lace-like skeleton. The easiest control is to hand-remove the offending beetles by gently shaking them into a jar of soapy water. The soap breaks the surface tension of the water and the beetles meet an untimely demise in the liquid. Don’t bother with the adult insect traps. Research has shown they attract more beetles to your yard than the trap collects!

The Japanese beetle females begin laying eggs in the soil during July and August. The white grubs that result devour grass roots, eventually causing patches of home lawns to turn brown and die. Control is only warranted when grub populations exceed ten per square foot. While it’s possible to wait for the birds and skunks to effectively remove the offending grubs, most homeowners prefer a more proactive stance.

Biological control methods center on introducing natural enemies, such as nematodes, parasites and bacterium (such as BT, Bacillus thuringiensis, and milky spore, Bacillus popillae) to adult or grub populations. When successful, the organisms are slowly able to suppress this insect to manageable levels. While biological agents have been successful in southern climates, research results in New Hampshire have not yet shown effective Japanese beetle control using these products.

To learn more about this topic and for a list of recommended insecticides, read the UNH Cooperative Extension publication, Insect Pests of Home Lawns, at http://extension.unh.edu/Pubs/HGPubs/InsPHL.pdf.

Q: Is the mold that grows on my tree’s bark harmful? It looks like it’s growing everywhere—on both branches and the main trunk.  —Alan Eaton in Newmarket, N.H.

Lichens are not harmful to the overall health of landscape trees and shrubs. Their unsightly appearance more often coincides with overall plant decline resulting from other environmental or mechanical factors.

It’s not uncommon to see fungi, algae, lichens or moss—non-parasitic organisms—growing on rocks, trees and other exposed surfaces throughout our native forests and fields. They are part of a wonderful ecosystem that absorbs moisture and nutrients following a rainstorm and provides habitat for invertebrate animals that are enjoyed by bark-foraging birds, among others.

Sometimes, we find lichens attached to the branches and trunks of ornamental trees and shrubs in our landscapes. They cause alarm for homeowners unaccustomed to their unsightly appearance, since they often appear on tree limbs showing signs of decline. The lichens are not harmful—they’re merely freeloaders along for ride.

Lichens are actually formed by the symbiotic association between alga and fungus each providing to the other for their mutual benefit. The green/blue-green algae photosynthesize valuable nutrients while the fungi furnish shade, moisture and protection for their companion. While their relationship may not be fully explained, it is a stable one with extreme longevity. Some of the arctic-alpine lichens have been estimated to range from one hundred to 450 years old!

We often notice lichen on our trees and shrubs when they begin to lose their branches. The open canopy allows additional sunlight to penetrate to the bark surfaces and lichens enter this non-competitive environment. Most lichens will not thrive on heavily shaded twigs and branches of healthy woody plants.

The best defense against lichen growth is to promote healthy plant growth. Determine the cause of your plant’s decline and seek answers to question such as these. Is the soil compacted?

Is the plant starved for nutrients? Has prolonged drought been a factor? Does the tree need to be pruned to encourage new growth? Has it been compromised by disease, animal or equipment damage? Has shade overcome a once sunny landscape, negatively affecting sun-loving species?
 

Nancy E. Adams recently retired after a 24-year career as a horticultural educator with UNH Cooperative Extension. Her business, HortaQuest, offers on-site horticultural consultations for home and commercial landscapes. Finally, someone who makes house calls! Contact her at hortaquest@comcast.net or 603 969-4855.