Garden Notes: Viburnums and lilacs

Put scent in your spring air.


Mornings are light by 5:30. Birdsong is increasing, as staking out territories intensifies. Suddenly, vernal greenery surrounds us. This happens every year, but is inching earlier and earlier each year, too.

Climate Action Week started May 8 here. As with Earth Day being every day, Climate Action Week is every week. (Lilacs in bloom by Mother’s Day? Instead of Memorial Day?) What action(s) will you take?

Viburnums: Perfuming the garden
Whether from Edgeworthia (still!), lily of the valley, viburnum, or lilacs, May might be called the perfume month. Being surrounded by perfumed air is a welcome spring experience, and one that gardeners have the power to create.

As soon as I submitted my last column, I realized I should have included fragrant viburnums, as they are just now in bloom. The convincing reasons for this: Viburnums are well-adapted to our conditions and acidic soils. Their fragrance is sweet and powerful.

Michael Dirr’s “Viburnums: Flowering Shrubs for Every Season” and “Manual of Woody Landscape Plants” are reliable sources for propagation advice and further information about the wide variety of viburnum species and cultivars.

Other viburnums, less fragrant, come into bloom later: the native, arrowwood viburnum, V. dentatum, and its morphological permutations are major habitat components of the Island woodland understory and ecology. Doublefile viburnums and cultivars, European cranberrybush viburnum, V. opulus, and American cranberrybush viburnum, V.trilobum, are seen in plantings Island-wide. Occasionally encountered in Island woodland is V. cassinoides, the witherod viburnum. The tea viburnum, V. setigerum, a nonfragrant and non-native species I have planted in several landscapes, produces good fall color and showy fruit. It supplies height for screening in mixed, naturalistic plantings. Leaves have medicinal properties, and are used for making tea.

I grow three fragrant cultivars: V. carlesii; semi-evergreen (name lost) V. x burkwoodii; and V. x burkwoodii ‘Mohawk.’ Many of the fragrant ones in bloom, wafting their heady perfume, seem to have miraculous superpowers to spread it.

All disperse spicy fragrance, and are handsome shrubs for a sunny to partly shaded location, or perhaps an open woodland garden. ‘Mohawk’ and V. carlesii have the added bonus of fine fall color, in the deep red-maroon-burgundy range. V. carlesii var. ‘Compactum’ is joined by several more recent, smaller carlesii introductions; thus the smaller garden is not deprived of this intoxicating scent.

In addition to the three above, V. x carlcephalum and its cultivars have a degree of the same fragrance and bloom slightly later, extending this season. A superior seedling selection, ‘Cayuga,’ exhibits good fall color. I do not grow V. x juddii although it too is good for fragrance and fall color.

Visit Polly Hill Arboretum to see (and smell) its viburnum collection. Depending on a variety of factors, viburnums as a group produce showy fruit, and thus contribute to pollinator- and wildlife-friendly gardens and landscapes. Deer browse may be a problem on viburnum, or they may leave plants alone if there is other browse available.

Viburnums are a generally healthy plant group, despite increased presence of viburnum beetle on the Island. Viburnum clearwing borer damage is similar to that of other forms of borer: In winter, look for the keyhole-shape holes in larger canes and prune out. Prune to shape or control height. 

Lilacs too
Also evocatively fragrant, a quick note about these plants of quintessentially New England gardens and doorways. Many clumps of old-fashioned lilac, Syringa vulgaris, came to be that way because they are colonizing plants, producing suckers from the bases and spreading outward.

Younger canes are generally more vigorous, and this is the most floriferous wood. Older, larger trunks are likely to be chosen by lilac borer as sites for hosting their larvae, creating dieback and general lack of vigor in them. Cut these down in winter, when the insects are inactive, since the scent of the cut lilac wood attracts them.

Newer cultivars of S. vulgaris may be suckering or nonsuckering; some have been bred to rebloom. If you lack room for a spreading lilac clump, research your preferred cultivar before planting. Pictured, ‘Président Grévy’ (Lemoine, 1886, one of the glorious French hybrids, cultivars dating from breeding work in France before World War I) is a nonsuckering, double blue.

Unlike viburnums, lilacs prefer basic soils, as they are native to limestone areas. Here, they do well on either side of neutral soil pH, top-dressed with lime from time to time to raise it. Generally easy and unfussy as to soil type, give lilacs a sunny location and avoid soggy soils.

In old, grown-over fields, sassafras, Sassafras albidum, is one of the nurse species that converts pastures to woodland. Just now the candelabra effect of budding sassafras stands out against the woodland background. Sometimes disliked because it emerges from old, buried rootstocks in the midst of immaculate, controlled landscaping, did you know that sassafras supports many bird species, and is a critical larval food plant for spectacular moths and butterflies such as spicebush swallowtail butterfly, and promethea, angulifera, regal, and imperial moths?

In the garden
Pruning: if it blooms before June 21, prune after bloom. If it blooms after June 21, prune now.

What aren’t we doing in the garden?

Lawns; cleanup; digging, dividing and replanting perennials; deer spraying; poison ivy control; English ivy control; invasive vine (greenbrier, Virginia creeper, weed clematis, bittersweet, Japanese honeysuckle, grapevine, nightshade, in hedges) control; pruning back the sub-shrubs (potentilla, hypericum, Montauk daisy, buddleia, perovskia, lavender, santolina, hydrangea, etc.) by one-third; judicious setting out of plants carefully started indoors; cut asparagus; tick check every night.

Notice emphasis on the word “control”? Ah, in some other reality, all that “control” works; in our world, it does not. The concept of control is an illusion, one to be taken with a grain of salt. Try to relax — enjoy yourself in your place, in your gardening, in your lawncare. Red thread happens. So does frost.

Accept that “we don’t have perfection, but we know what it is.”