Martha’s Vineyard gardeners prepare for summer

Proper soaking rains have alleviated the dryness, the odor of rotting pollen, and the pollen itself, which had been affecting the soil and air.

We have less than a week before the summer solstice. This is the last call to prune spring-flowering shrubs such as viburnum and forsythia, and administer the “Chelsea chop.” After this, plants go into a different mode, one of hardening off soft growth and initiating the next flowering buds to come.

Cut or pinch out the growing point of herbaceous perennials such as asters, chrysanthemums, echinacea, and phlox. Pinching creates more flowering stems, stockier plants, and lessens the need for staking. It also helps to retard bloom-times, extending color into August. Pinch growing points of dahlias after the third set of leaves appears, then pinch the resulting sprouts again, for floriferous, bushy plants. Do not pinch perennials such as poppies, true lilies, and daylilies.

Deadheading and clean-up starts in earnest too, as the stars of the spring garden go by. Siberian and bearded iris, peonies, poppies, centaurea, delphiniums, and first-flush roses can be cleaned up before they self-sow or decompose. On the other hand, early bloomers and biennials, such as columbines, foxgloves, hesperis, and lunaria, may be encouraged to self-sow or to spread into other garden areas, by careful ripening and placement of seed heads. Groom flowering annuals.

Need for staking becomes apparent with windy or rainy weather. Try for a neat, unobtrusive job using twine and bamboo stakes.

Insect impacts

Lecanium scale appears to be widespread in Island woodlands and on landscape trees. The insect has been reported elsewhere in New England; however, the UMass landscape message contained no mention and an Internet search yielded little information that was up-to-date or for our region. The trees, mainly oaks, at our place now hosting scale insects are survivors of earlier winter moth/fall cankerworm outbreaks. They must continue to be under duress, but why?

Some information below has come from www.uvm.edu/~pmrc/lecanium_scale_info_sheet.pdf and from http://branchoutburlington.org/pests/lecaniumscale.htm.

Where possible, help trees recover from stress: “Heavily infested trees may show some dieback of twigs and branches and there may be some early leaf drop. Landowners can reduce other stress on trees to help them recover. For landscape trees, avoid disturbances such as pruning and root damage. For forest trees, postpone plans to thin or harvest trees until after the outbreak. Thinning can allow drying of soil, stressing trees.”

Dormant oil sprays are effective on scale insects, especially in July/August, when they are in the “crawler” stage.

Care of boxwoods

“Most gardeners are…generally aware of boxwood, but few are aware that it is Man’s oldest ornamental plant.” I turned to the “Boxwood Handbook,” by Lynn R. Batdorf (published by the American Boxwood Society), from which I took that quote, to gather information about boxwood psyllid.

This common pest of boxwoods is in evidence now, with whitish, waxy “dandruff” on new growth. If they are allowed to remain, the psyllids cause disfiguring cupped leaves on boxwoods. Insecticidal soap is the best control for this, from the viewpoint of both human and plant, applied in April when new growth emerges, and then again about three weeks later.

Elsewhere in the handbook, Mr. Batdorf recommends that shearing be done in early June, but only when accompanied by thinning of boxwoods in late November. Shearing is highly stressful for boxwoods. It encourages dense, multiple-tip branching, leaves are cut in half, and disease is more prevalent, he writes. Thinning, also known as plucking, permits the inside of the shrub to receive light and air, which will encourage the growth on the inner stems and lessen disease potential.

English Boxwoods of Virginia, at englishboxwoods.com, contends on its web site that the ideal look to be sought in boxwood is the traditional cloud-like texture. Boxwoods “are not pruned with shears but thinned by breaking out stems from the body of the plant before new growth occurs. This creates small holes for air and light over the surface of the plant allowing growth within. Once a year clean the plant’s interior with a strong hose spray to remove all debris to aid air circulation and help prevent disease and aerial roots. For the detailed description of plucking (thinning) and cleaning go to englishboxwoods.com/plucking.”

Styrax

The air at our house is redolent with the heavy scent of Styrax japonicus, a beautiful, June-blooming small tree acquired in 1996 at an Arnold Arboretum plant sale. I do not understand how the great authority, Michael Dirr, can characterize it as having “slightly fragrant” flowers! Is it possible mine was mis-tagged? (Other, previously unavailable species of Styrax have entered the nursery trade since the opening with China in the 1980s.)

It is the flowering of Styrax that makes them irresistible, although the foliage and general habit are attractively garden-worthy as well. Dr. Dirr lists about 18 cultivars of S. japonicus in the “Manual of Woody Landscape Plants,” including weeping, vase-shaped, fastigiate, and pink-flowered forms. Polly Hill Arboretum’s collection contains about ten species; go there for a closer look at this alluring genus.

Polly Hill Arboretum’s gardens are full of more interesting plants blooming or exhibiting other unique qualities. A June visit can be eye-opening to the many, many possibilities for Island gardens. PHA’s June calendar contains interesting programs too, which may be seen at pollyhillarboretum.org/calendar-at-glance.

Open gardens: Garden Conservancy tour

Explore three private gardens in Vineyard Haven and West Tisbury, that will be open to the public for self-guided tours, on Thursday, June 30, 10 am to 4 pm to benefit the Garden Conservancy. The cost is $5 per garden, children 12 and under free. No reservations required; rain or shine. Begin at East Hill, 133 Pasture Gate Road, Vineyard Haven, 888-842-2442; see website for additional locations: gardenconservancy.org/opendays/open-days-schedule.