Gardening

Planting Depth for Grafted Trees and Shrubs

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It’s usually best to slightly bury the bud union of grafted trees, conifers and shrubs.

Grafted woody plants – trees, conifers, roses, etc. – are more and more common in nurseries. In such plants, a desirable variety is multiplied by grafting it onto a wild seedling of the same or related species. This gives faster results that growing plants from cuttings, plus many plants that are very difficult to grow from cuttings are easy to graft. Grafting can be done at various heights, but in most cases is done just at the base of the plant, near the ground. Normally you would never plant a woody plant deeper than it was in its original pot, but here may be worthwhile making an exception.

That is because the bud union, that is the usually swollen node at the base of the plant that indicates the junction between the scion (desirable plant) and the rootstock (wild plant), will remain a weak point throughout life of the plant, subject to frost, fractures, cracks, insect infestations, diseases, etc. Just wind rock alone (the force of the wind pushing the top growth back and forth) can do damage. However, if you bury the bud union, not only will you reduce wind damage, there is an excellent chance that the scion will begin to produce its own roots and thus “free itself” from the rootstock over time, becoming an “own-root” plant and overcoming many of the problems mentioned. It is not necessary to bury the bud union very deeply: 1 to 2 inches (2 to 5 cm) is usually enough. Burying the bud union is even more important in cold climates than warmer ones, as alternating periods of freezing and thawing are even more likely to damage the bud union.

A secondary advantage of covering the graft with the soil is that it tends to reduce suckering at the base of the plant, a common problem with grafted plants.

Exception to the Rule

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Dwarf fruit trees are an exception: leave their bud union above ground.

Of course, there are exceptions to every rule and here is one. When you buy dwarf and semi-dwarf fruit trees, you’ll notice the bud union is not at ground level, but about 2-4″ (5 to 10 cm) higher. There’s a reason for that. Here the rootstock is not a wild seedling, but a specially chosen variety designed to reduce the growth of the upper part of the tree, making it easier to harvest. If you bury the bud union of a dwarf or semi-dwarf fruit tree, the scion will eventually put out its own roots, begin to grow normally… and the dwarfing effect will be lost.

So, bury the bud union on most woody plants, but leave the bud union of dwarf fruit trees exposed.

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.

2 comments on “Planting Depth for Grafted Trees and Shrubs

  1. Awesome! Thanks for this article. I’m sick to death of planting fruit trees and 5-10 years later when I’m supposed to be harvesting, they’re dead. I’ve been wanting to experiment with burying the graft, but this is a long, expensive experiment. I have some Stanley plums coming and I’d like to have mature producers some day like my grandpa did!

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