Gardening Laidback Gardener Tip of the Day Shrubs Trees

When Top-grafted Shrubs Sucker

20160727A
This cutleaf weeping peashrub (Caragana arborescens ‘Walker’) is being taken over by suckers growing from its base: they should have been removed while they were still young.

Shrubs and trees grafted onto an upright stem are very popular in our gardens. They may have different names – I hear “top-grafted”, “standard”, “dwarf standard”, “tree form” and “dwarf tree” – but most are created in the same way. A shrub or small tree, often with a weeping or rounded habit, is grafted onto the top of a single upright stem (called the rootstock) to create the effect of a miniature tree.

20160727E.jpg
Top-grafted weeping pussywillow (Salix caprea ‘Kilmarnock’)

Among the most popular top-grafted shrubs are weeping forms of regular shrubs, like weeping peashrub (Caragana arborescens ‘Pendula’ and ‘Walker’), weeping pussywillow (Salix caprea ‘Kilmarnock’ and ‘Pendula’) and weeping mulberry (Morus alba ‘Pendula’). If they grew on their own roots, these mutated forms would simply creep along the ground, but raised on a trunk, they drip down beautifully and become mini-stars!

20160727D.jpg
Top-grafted dwarf Korean lilac (Syringa meyeri ‘Palibin’)

Among mini-trees with a rounded top – those with a lollypop look to them – you’ll find dwarf Korean lilac (Syringa meyeri ‘Palibin’), dwarf winged euonymus (Euonymus alata ‘Compacta’) and tree roses (various cultivars of Rosa), but there are many, many more.

There are also top-grafted evergreens of all sizes, colors, and shapes.

20160727B
Sucker growing from the base of a tree.

These “mini-trees” are certainly cute enough, but do have their flaws, including, in many cases, a tendency to sucker at the base. These suckers (new growths sprouting from the roots or the base of the trunk) will not, of course, be the variety you chose: the growths appear from the rootstock, a variety chosen for its straight trunk, not its weeping or bushy habit.

For example, a weeping peashrub is produced by grafting a weeping cultivar (C. arborescens ‘Pendula’ or ‘Walker’) onto the stem of C. arborescens ‘Sutherland’, a cultivar with exceptionally straight stems. If suckers appear at the base of your plant, they therefore will show nothing of the drooping stems of weeping form, but instead the narrow upright branches typical of ‘Sutherland’.

Branches can also appear on the trunk of the weeping tree (if so, they are officially called watersprouts rather than suckers). Since they will be sprouting from below the graft on top of the plant, they too will come from the rootstock, leading to branches that don’t conform to the weeping or dense plant above.

Some top-grafted shrubs are abundant producers of suckers or watersprouts (weeping peashrub and tree roses, for example), others do so only occasionally. Sometimes suckering occurs when the top-graft is dying back for some reason, but other plants will produce suckers or watersprouts even when the top is growing vigorously.

Taking Action

20160727C
Just prune off any growth from the rootstock, whether at its base or on the trunk.

The solution is simple enough: just prune off the unwanted growths! Use pruning shears, cutting as close to the junction point with the grafted tree as possible. If suckers appear from the ground next to the mother plant, you can even remove them with a sharp shovel. There is no particular season for sucker removal: when you see one, just cut if off.

If you fail to remove suckers and watersprouts, they’ll eventually take over and smother your mini-tree (see the photo above), as they are usually faster growing and more dominant than the top-graft. Soon your mini-tree will look nothing like a tree at all. So, if mini-trees are your thing, you may have a bit of pruning to do.20160727A

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.

1 comment on “When Top-grafted Shrubs Sucker

  1. I have several Dwarf Korean Lilacs, and you sure caught my interest with that beautiful photo above. 🙂

Leave a Reply to Judy @ NewEnglandGardenAndThread Cancel reply

Sign up for the Laidback Gardener blog and receive articles in your inbox every morning!

%d bloggers like this: