Gardening

Laidback Gardener Tip of the Day

Top-grafted Trees: Rarely a Good Choice

septembre 1
Caragana arborescens ‘Walker’s’

You’ve all seen them: miniature trees with a straight trunk and a ball of foliage on the top or long branches that weep to the ground. They’re called top-grafted trees, because they are created by grafting one type of tree (actually usually a shrub rather than a true tree) on top of the upright stem of a related plant, giving the impression of a small tree. Weeping varieties such as weeping caragana (Caragana arborescens ‘Pendula’) or weeping larch (Larix decidua ‘Pendula’) are the most common, but you’ll also see what I call green lollipops: rounded shrubs grafted on a stem, such as dwarf lilac Korea (Syringa meyeri ‘Palibin’) or tree roses (Rosa cv). These plants can seem like a really great idea, because they never grow in height and provide a miniature tree effect that fits well into many landscapes… but sadly they rarely live very long. Here’s why:

In plants, a graft remains a weak point for the plant’s entire life. When the graft is at the base of the plant, as in dwarf apple trees, it is relatively well protected from the elements and usually will survive for decades. But in top-grafted trees, the graft, as the name suggests, is at the top of the stem. Therefore it is always exposed to the elements: sun, cold, wind, heavy snow, ice storms, etc. Sometimes the grafted part simply gets too heavy and snaps right off the “tree”. As a result, probably not 3 top-grafted trees out of 5 are still alive 5 years after they are planted. After 10 years, not 1 in 5. Even when they do survive for a few years, often half of the graft dies, creating an unbalanced effect, with all the growth occurring on one side. There are always exceptions, of course: a top-grafted tree that lives a normal life and survives as long as any other specimen of its species, but these are the exception to the rule.

These mini trees are expensive, short-lived and prone to suckering, frost cracks, insect infestation, pernicious rot and much more. The wise gardener will avoid them and plant something cheaper and longer-lived.

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

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