Pruning Forsythias to Enhance Flowering

In early spring, beneath the soft and subtle green of oak leaves, the bright yellow of forsythia (Forsythia x intermedia) covers the New England landscape.  I believe states must be offering tax breaks to homeowners who grow this herald of early spring, for few properties are without at least one shrub, and some citizens compete with the highway department for the largest colony.

An old informal forsythia hedge that has been properly pruned over the years.

An old informal forsythia hedge that has been properly pruned over the years.

One year, on an April journey across Massachusetts, Marjorie and I documented the many forms that forsythia assumes in home landscapes.  We photographed wild and woolly hedges that had not been pruned in decades, a few slender flowering branches twisting into the light from a tangle of old woody stems.  Other informal hedges, open and airy and far more floriferous, reflected the care of annual pruning.

And there were all of the tortured forms, meatballs lined up along the property line, hot-air balloons flanking the entrance drive, and flat-topped plants that might be used

Pruning forsythias into unnatural shapes is plant butchery.

Pruning forsythias into unnatural shapes is plant butchery.

as garden benches.  Forcing forsythias into unnatural shapes is plant butchery.

For my taste, the best forsythias are those managed to enhance their natural growth habit, slender branches that grow upward and outward, stiffly arching down to earth under the weight of spring flowers.  This can be accomplished with a single plant, a small grouping, or a long informal hedge.

Forsythia flower buds form during the summer on one-year-old branches that grow off of older branches or from ground level.  As a branch ages, its flowering potential is reduced and plants with an abundance of old branches thicker than an inch in diameter often bear few if any flowers.  Also, shearing plants into unnatural forms removes many flowering stems and shortens the length of others, thus reducing the total number of flowers.

The gardener's task is to encourage the production of young floriferous stems.

The gardener’s task is to encourage the production of young floriferous stems.

The gardener’s task is to enhance the proportion of young, floriferous branches and this can be accomplished with annual pruning.  Each spring, as soon as the plant stops flowering, prune one-third of its stems, choosing the oldest and thickest.  Give priority to stems that are rubbing against each other as this rubbing will eventually wound one or both of the stems, allowing disease to enter.  Cut most of these old stems, particularly the thickest, back to the ground, others a few to several inches above the ground, varying the height of the cuts to maintain a natural form.  Make each above-ground cut just above an outward facing bud.  New stems will then grow outward from lateral buds, stems that will grow vigorously during their first year and flower profusely in their second and third years.

While pruning each plant, you should also remove any dead, damaged, or diseased stems, regardless of size, again making each cut either just above an outward-facing bud or at ground level.  Pruning for these “three D’s” should be done throughout the year, whenever they are noticed.

An old neglected forsythia will be crowded with thick old stems that bear few flowers.

An old neglected forsythia will be crowded with thick old stems that bear few flowers.

If you find yourself confronted with an old forsythia that has not been pruned in years, more drastic measures must be taken, and they should be taken in early spring before new growth begins.  Waiting until after flowering, when the plant has leafed out, will make it more difficult to see what you are doing.  The center of the old neglected shrub will likely be a tangled cluster of old gray or brown warty stems rubbing against one another.  You must remove enough of these stems to eliminate their touching.  Make the cuts as close to the ground as possible, always selecting the thickest stems to remove.  Continue cutting these stems out until you have created an open, airy center to the plant.

Pruning forsythias, even informal hedges, should be done with hand-pruners, loppers, and a small pruning saw.  Under no circumstances should any form of pruning shears be used!  Shears lop off stems at indiscriminate points – you want to make each cut just above an outward facing bud.

Forsythias are in full bloom on the shores of southern New England and will soon be opening their flower buds in Marjorie’s Garden.  Wherever we find them pruned to highlight their graceful habit, their upright-arching stems festooned with bright yellow flowers, they serve as lovely harbingers of the new garden year.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: http://www.facebook.com/pages/The-New-England-Gardeners-Year/187285218055676.)