Laidback Gardener Tip of the Day

Trees with Invasive Roots

The weeping willow (Salix x sepulcralis ‘Chrysocoma’) may be a good choice for an urban park, but don’t plant it near a house.

I regularly get questions from home owners worried by the presence of a tree near the foundations of their house or near water or sewer pipes. Usually, however, there is no problem unless the tree is so close to the foundation that its trunk or branches actually rub against it.

Pipe clogged with silver maple roots (Acer saccharinum).

However, there are are a few trees that should not be planted near a house or underground pipes. These trees have roots that are long and invasive and are known for their ability to block drainage pipes, invade septic tanks and work their way into the cracks of a foundation and thus damage the house. In many municipalities, it is in fact illegal to plant these trees… which doesn’t stop local garden centers from selling them! Check before planting any of the following trees and If you are allowed to plant these trees, plant them at least 100 ft (30m) from any building, pipe, drainage system or septic tank.

Here is the short list of culprits for temperate climates:

American elm (Ulmus americana) Zones 3-8
Poplar (Populus spp.) Zones 2-7
Silver maple (Acer saccharinum) Zone 2
Willow (Salix spp.) Zones 1-10

Note that the shrub willows pose no problem; it is the tall tree willows that are harmful.

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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