Most Frequently Asked Questions: Summer

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What are the guidelines for watering the lawn during the summer, especially during a drought?
To effectively work with the watering constraints imposed during a drought, limit water-demanding turf areas in your landscape. A reduced lawn area will be much easier to water more efficiently.

Ways to keep the lawn green are:
  • Select grasses for drought tolerance; they will go dormant in drought, but green up again as soon as rainfall begins.
  • Leave grass clippings on lawn to conserve moisture and return soil nutrients.
  • Keep lawns high keeping grass at 2-3"mowing height (varies according to grass species).
  • Water early in the morning when evaporation loss is low.
In order to avoid wilting, lawns need about 1" of water per week in spring. This will encourage deep rooting before summer sets in. If this does not occur as rainfall, then supplemental watering will be necessary. As the temperature goes higher more than one inch may be needed to keep lawns looking their best. To determine the proper amount of supplemental watering, place measuring devices such as rain gauges and/or containers around the lawn. If rainfall does not supply the amount needed, then use your watering system to make up the deficit. You will need to figure out the amount of time it takes to deliver ½" of water and use that time as a guide to supply the right amount. Turn on the sprinkler system, and when there is 1" in the container that is how long it needs to run.

What are the guidelines for watering trees and shrubs in summer, especially during a drought?
Trees and shrubs are important landscape assets, and trees are particularly important to the overall environment. In the event of a horticultural drought, decide to water your trees first, then shrubs, herbaceous plants, and finally lawns. Deep watering early in the morning encourages roots to grow deeply and strongly. It is best to use a soaker hose to reduce water waste and prevent disease problems by keeping the foliage dry.

When leaves droop and fold the plant is under stress and it is time to irrigate. It is best to water early in the day, when the evapotranspiration rate is lowest; leaves should be open to be capable of full photosynthesis during the day. Do not leave foliage wet at night, as this will encourage disease.

How can I get rid of the slugs that are eating my plants?
Slugs feed at night and on damp, cloudy days. By keeping the area around your foundation clean and free of debris, you can help to eliminate their hiding places. You can hand pick them and dispose of them in a pail of soapy water (a rather unpleasant task). Or, they will drown in shallow containers filled with beer, sunk into the ground with the lip at ground level. These containers will need to be emptied each day. Barriers, such as diatomaceous earth or crushed eggshells, can be placed around your plants as well. These materials work by piercing the bodies of slugs and other pests, causing desiccation. Cautionary note: beneficial insects are also vulnerable, so use diatomaceous earth only around specific problem areas.

How can I get rid of Japanese beetles?
The Japanese beetle is a very destructive landscape pest. The adult attacks the flowers and foliage of hundreds of plant species while the larvae eat grass roots. The best long-term control of future populations is to target the grubs, which overwinter in the soil and emerge as adults in spring. Milky spore (a bacterium), applied to the lawn, causes a lethal disease specific to the Japanese beetle grubs. It does take a few years to become effective however. For adults, hand pick the beetle and discard in a pail of soapy water. Use a neem oil spray to attack them. Keep in mind that many birds such as cardinals, catbirds, and grackles are the natural enemies and favor the grubs or beetles, or both. So try to attract birds to your garden.

How can I control powdery mildew on my roses?
One of the least-toxic and most effective controls for the powdery mildew fungus is the Cornell formula. The formula is 1 Tablespoon of baking soda and 1 Tablespoon of light vegetable oil or summer weight horticultural oil added to 1 gallon of water. Shake well.

Spray both the top and underside of all leaves once a week, or following a heavy rainstorm.

What trees and shrubs are pruned in summer?
In general, prune all shrubs and ornamental trees to keep them shapely. Broken branches and cross-branching always need to be removed. Specifically, prune climbing and rambling roses after their first flush in spring and continue to deadhead all other roses throughout the summer growing season to increase flowering. Trees that produce sap in spring such as beech, birch, maple and sycamore are best pruned in summer. Early spring-flowering shrubs such as forsythia, spirea, rhododendron, etc. should be pruned now. Evergreens like yews, boxwood, and arborvitae need touch-up pruning in early summer after their growth has slowed.

I'd like to start a cutting garden. What flowers can you recommend?
Flowers for a cutting garden need strong, medium to long stems with long-lasting flowers. These flowers can be integrated into the existing garden design, but for a steady supply of bouquets and ease of gathering, it is recommended to devote part of the garden specifically for cutting. It is really only necessary to create an area that can be reached into easily for gathering and cutting the stems. Good choices for the cutting garden include Achillea, Dahlia, Coreopsis, Echinops, Echinacea, Gaillardia, Liatris, Phlox, Salvia farinacea, Veronica, and Zinnia, etc. There are many beautiful flowers to choose from. Visit your local botanical garden for ideas.

How can I attract hummingbirds to my garden?
The ruby-throated hummingbird is the only one found regularly in our northeast area. Its arrival in spring coincides with the blooming of certain nectar-producing plants with which it has coevolved over the millennia. Nectar plants provide a high-energy food source for these tiny creatures who can produce up to 200 wing strokes per second. Planting native species that the ruby-throated hummingbird knows as a reliable source of nectar is an important consideration in encouraging visitation. These plants include: Monarda didyma, Asclepias tuberosa, Dicentra exima, Lobelia cardinalis, Ipomoea coccinea, Polygonatum biflorum, and Aquilegia canadensis. Some shrubs, although not native, are attractive sources as well: Weigela, Hibiscus and Kolkwitzia.

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