Garden Notes: Conjunctions, fruit trees, and summer

And some thoughts on controlling lilac borers.


Why do you suppose there is so much trash appearing recently along Island roadsides? Just asking. Respect our Island home!

A taste of winter provided by the large storm system overflying the region on Thursday eliminated hopes for a white Christmas, with wind, rain, and sleet dissolving the beautiful effects. The mainland was not so lucky; although the hope is that the winter storm slowed coronavirus’ spread everywhere.

‘Great’ Conjunction

Because this article is due early, I only mention as prospect, not fact, that many Islanders will be able to view the ‘Great’ Saturn-Jupiter conjunction on Dec. 21. The timing, coinciding with the winter solstice, is happy and special. The celestial event should be awe-inspiring if the weather cooperates; at the moment, the forecast looks favorable.

What makes this a ‘Great’ conjunction, and unique? It refers to the nearly 400 years since the planets passed this close to each other in the sky, and nearly 800 years since it occurred at night, allowing nearly everyone on earth to witness it.

Find a location with unobstructed sky, and look to the west or southwest just after sunset. The two bright objects will be easy to see with the unaided eye; however, a telescope or pair of binoculars will enable greater detail to come into focus. Here’s some information:

Lilacs: Controlling Borer

The lilac borer is well entrenched on the Island now; I find evidence of it in almost all the mature lilacs I see here. The lilac borer damages lilacs by laying her eggs in late spring and early summer in larger or older stems, where the larvae develop and feed. Stunted growth and flowering result.

Now is an appropriate time to take action against this injury. The wounds from pruning lilacs in late spring and early summer actually attract borers; doing it now eliminates that risk.

Without foliage, the evidence of borer activity is easier to spot: look for keyhole-shaped holes in larger trunks. Lilac borer may also afflict overgrown privet. Look for the same telltale keyhole-shaped holes in larger stems. Prune these trunks out, and if they are “firewood grade,” by all means — fire pit or stove — burn them.

Pruning Fruit Trees

We have the rest of the winter, until March, to improve orchard trees through pruning, but there is no reason not to start now. Trimming stimulates new growth, so best to aim for removing not too much. Quoting Tim Boland of Polly Hill Arboretum, “growth follows the knife.”

Aim to open the canopy: the “goblet shape,” for light and air to the tree’s center. Remove anything whippy or resembling a watershoot arising directly from the trunk. Look for rubbing or crossing branches and acute angles: correct these. Split-resistant, wide angles, and strong crotches are desirable.

It is the younger, more vigorous wood, also nubby growth with spurs, that produces flowers and fruit, which we aim to maintain. Timely pruning keeps it productive without removing too much at once. Work around the tree, so that cuts are distributed evenly. Use pruning saws and clippers that are sharp, and remember to cut just outside the branch collar, the ridge of bark marking the juncture of trunk and branch, encouraging the tree to callus over the cut.

Looking Ahead to Summer

The National Garden Bureau has declared 2021 as the Year of the Hardy Hibiscus. Hibiscus, in the Malvaceae family along with hollyhocks, okra, abelmoschus, and many others, comprises three groups: the shrub rose-of-Sharon, tropical hibiscus, and hardy hibiscus. According to Allen Armitage’s “Herbaceous Perennial Plants,” the genus contains over 200 species, mostly from tropical and sub-tropical regions.

The hardy hibiscuses are the mallows and their hybrids. We are fortunate to have H. palustris as native wildflowers here, ringing Island estuaries and ponds. In August, daily traffic drives past a flourishing colony at Parsonage Pond in West Tisbury.

Hardy hibiscuses have been hybridized to produce plants with flowers of dramatic color and size. The principal species used are H. moscheutos and H. laevis. Not for nothing are they sometimes called “dinnerplate” hibiscus. They are sun lovers and true perennials, at least as far as zone 7, and die back to the ground each year, leaving punky woody stalks to mark their location.

As noted above, these hardy hibiscuses are happy in damp to very wet soils, and thus make excellent choices for swales and rain gardens. However, once established, they are usually fine in ordinary garden soils too.

Hardy hibiscus flowers in shades of white to pink to deepest red, with a few yellows, are available too. Blooms may be splattered, or often contain a deeper-colored eye; foliage colors range from light green to darkest burgundy, sometimes deeply cut.

Look for longtime favorites such as the seed-sown ‘Disco Belle’ series, white ‘Blue River II,’ pink with red centers ‘Lady Baltimore,’ crimson ‘Lord Baltimore,’ and enormous pink ‘Sweet Caroline.’ Newer introductions include the Summer Spice series, the Luna series, and the Summerific series.

My experience with hardy hibiscuses is they are late to emerge in spring. Mark their location to avoid damaging new shoots, if the woody stalks were removed the previous autumn. We make a practice of trimming them uniformly and leaving them, to provide built-in supports for the next season’s growth, which can be sprawling. Simply loop twine from stalk to stalk to contain the coming season’s growth.

Hardy hibiscus are altogether “knock your socks off” plants for the sunny garden in late July to August — fantasize that!

In the Garden

Leave the fluffy, passé flowerheads on mophead hydrangeas; they protect the buds lower down from damage that variable weather may cause. Cut down ornamental grasses before they shatter and scatter.

Remembering Jean Wexler fondly: an accomplished North Tisbury gardener, writer, cook, and literary soul. R.I.P.