Runaway May: Forsythia, flowing trees, and garden to-do list

Green is a color too. Floral effects are ephemeral; using plants with foliage interest rounds out the garden. Here, Carya glabra (pignut hickory) with colorful bud scales (1); pulmonaria (2); and Viburnum plicatum f. plicatum ‘Popcorn’ (3). — Photo by Susan Safford

May overwhelms, though in a generally welcome way. Perhaps no other month presents so much sensory overload and rapid change of our surroundings. Town and countryside alike undergo the metamorphosis from drabness to green vernality. Trees and shrubs leaf out overnight; plants’ growing points virtually explode out of the soil; long-awaited floral displays burst forth, scattering bud scales on the ground beneath.

One wishes to plead for this ineluctable seasonal onrushing to delay so one can take it all in. Time is too short. The “eyeblink” that is our lives, like the flowering of shadbush, is never more clearly demonstrated than in spring.


Forsythia has largely gone by and may be pruned now, following the general bloom-time rule: if it blooms before June 21, prune immediately after blooming. Examples would be forsythia, weigela, and various viburnums such as V. x burkwoodii and V. carlesii. If it blooms after June 21, pruning should occur in spring, examples being hydrangeas, rose-of-sharon, and clethra.

Recently a question arose about forsythia’s having male and female flowers, and did that account for varying growth habits. Forsythia flowers are perfect and not dioecious (plants whose flowers are either male or female).

Depending on the style of pruning, forsythia may be made to appear either stiffly upright or more gracefully fountain-like, and cultivars, mostly Forsythia x intermedia ‘Spectabalis’ hybrids, differ in respect to their stoutness and habit of growth. Some, the “55 mph” ones, grow strong-colored, bold, and coarse, while others are more refined, wispy, or paler-colored.

While the paler and more strongly colored forsythias each have their value, in my opinion, for hedges it is a mistake to mix them. One or the other is always going to suffer by comparison. Most forsythia branches are capable of tip rooting, similar to brambles. If they are sweeping the ground, prune back now, unless this outspread is desired.

A separate species of forsythia is F. suspensa var. sieboldii, the weeping forsythia. The graceful, arching aspect of garden hybrids is greatly exaggerated in this species, which makes a most wonderful curtain planting in situations such as high retaining walls and walkout basements. It may also be encouraged to climb into trees and other shrubs.

Dry weather

Dry springs are a well-known Island condition and are the norm for this time of year. Spring brush fires start easily and are common, as much outdoor work is being done. Please exercise extra vigilance, especially those of you who smoke, and monitor children’s play in woodland hideouts and forts (if possible).

Container plantings, seedbeds, and seedling plants in the garden dry out quickly. Rainfall may be sporadic, missing the Island entirely, or falling in short, drenching downpours that run off without penetrating.

Flowering trees

As May flowering commences, seemingly sent explicitly to get us out into our gardens, it sets off overwhelming desires for more, and more. “Flower-power” is often expressed in the desire for a flowering tree and is one of the keys to nursery and garden center sales for this month.

It is always time well spent to go out to Polly Hill Arboretum to have a look at what is in bloom now. A big advantage is that exact cultivar information is available for all arboretum specimens, meaning you can eliminate any guesswork and check for eventual height and spread and ideal siting conditions. In many instances, there is more than one cultivar or form to make comparison visually. Then you can go to the garden center or nursery and ask for the exact plant to be bought in for you.

There are many standards or criteria to apply to one’s choices, to be kept in mind, for when the flowers have gone by. While spring-blooming trees are spectacular, if the garden is small, what remains post-flowering needs to pull its weight too. Look at the foliage effects and the general shape, size, and habit of growth of the tree; all plants in the garden benefit from this metric.

What about the tree’s root run? Will it starve the other plants in the garden by shallow or extensive roots? How about eventual size? Will it respond well to containment pruning to keep it within the available space? Is the habit spreading or upright? Will it tolerate sharing a bed with under-planting? Bark interest? Need for sunlight? Moist or dry soil?

Keep in mind that there are choices that provide more than merely one-season interest. That ephemerally blooming shadbush being a case in point, it is also a bird magnet when its fruits ripen (some selections’ fruits even have human culinary uses), supplies fiery autumn color, and has a graceful shape even without leaves.

Public libraries are well stocked with heavily illustrated garden books, which unlike excerpted Internet resources, have been written by authors with fully-fledged points of view, and design or plant experience. The plant-lists these books contain may spark a previously unthought-of plan. Perusing these sources of information before making a purchase will reward you.

In the garden

It is not too late to lift and divide perennials in need of it, but due to the above-mentioned dry conditions, the divisions will need more after-care and attention. Cut them back and place an up-turned bushel basket or cardboard carton over plants after resetting and watering-in. Performing this yearly-recurring garden task earlier in spring enables plants to take off without setback. Make a mental note of what next spring’s division needs will be.

Place stakes so plants may grow around them and make them unobtrusive. Pinch out growth or administer the “Chelsea Chop” to plants such as sedum, phlox, shastas and Montauk daisies. Tidy and tie in climbing roses. Dividing narcissi is another perennially occurring garden task. Locating them is easier before foliage completely withers away.