Gone Gardenin’: Top-grafted and tree-form plants hardy and beautiful

Hey there, time traveller!
This article was published 15/08/2013 (4451 days ago), so information in it may no longer be current.

Trends in gardening are always interesting and in the increasingly competitive nursery industry every business is trying to outperform its competitor by coming up with the latest — hopefully for them, trendy — garden fashion.

New gardening techniques and styles are invented almost as often as the fashion industry changes clothing designs.

Luckily, most gardeners are sensitive to what will work and what will not, and planting a garden is a long-term investment. Few of us rip up our gardens every year just because they do not conform to the latest whim of the industry gurus. We do appreciate, however, innovations that we think are here to stay and that really add some unique beauty to our landscapes.

The last few years one trend that has really caught on and that many gardeners have embraced is the use of tree-form and top-grafted trees and shrubs. Tree-form shrubs are simply shrubs that have been pruned to one main stem, which has been trained into a trunk with a burst of foliage at the top.

Top-grafted shrubs, on the other hand, are created by grafting a shrub onto the stem of a different plant — the plants must be compatible for this to work. For example, Walker Weeping caragana is grafted onto the top of an ordinary caragana stem to create a weeping top on a four foot trunk.

Top-grafted and tree-form plants are often smaller than many regular shrubs and trees and so are very useful in today’s smaller urban landscapes. They are also useful to add vertical accents to beds and borders without overwhelming the surrounding plants as many regular trees and shrubs would do.

Top-grafted shrubs require regular care to perform well. They must be pruned annually for a number of reasons, one being to maintain the attractive rounded shape of the top grafted part.

Another reason to prune them regularly is to reduce stress on the graft by preventing the top from getting too large and heavy. The graft might split if it comes under undo stress by the weight of too much foliage.

Finally, any shoots that emerge along the interstem or suckers that emerge from the base of the shrub must be nipped off both to maintain the appearance of the standard and to prevent the suckers — which will be from the rootstock, not the top-grafted plant — from taking over.

Many top-grafted shrubs are flowering shrubs, so pruning of the top of these plants should be done right after they finish blooming so that the shrubs will set flower buds for next year. Leaving pruning until long after flowering has finished means that most of next year’s flower buds will be pruned off as well.

These specimen shrubs are useful in beds and borders as accents and anchors, and serve well as focal points in foundation plantings or island beds. They should not be crowded among other plants so that their form can be appreciated.

When purchasing a top-grafted shrub, it will probably have its trunk staked. This stake should be kept in place for the first year or so until the shrub has securely rooted in the spot where you plant it.

Although there are many tropical standards offered for sale in the spring — hibiscus being probably the most common — these plants are not hardy and are either treated as annuals or wintered indoors. There are many hardy top-grafted shrubs, however, that you can plant into your garden with the assurance that they will survive the winter.

Some of the hardiest are the caraganas, which are rated zone two. The top graft can be a globe caragana, a pygmy caragana (which can be clipped into a tight round ball), or a weeping caragana (Walker’s is probably the most popular).

Diablo ninebark is often seen as a top-grafted standard; its colourful foliage adds to its appeal. Double flowering plum provides a wonderful burst of bloom in the spring, while a globe blue spruce will provide year around interest. All of these are rated zone 2.

Many lilacs are top-grafted, among them Sensation, Minuet, Miss Kim, and Tinkerbelle; they are rated zone 2 or 3 and should survive our winters without any problem. If you want to try something a bit more exotic, yet hardy, Limelight Hydrangea is offered as a top-grafted standard by some local nurseries.

I think the trend to small tree-form top-grafted shrubs is going to be an enduring one. Local gardeners have found them to be useful plants in their landscapes, reliably hardy, and above all, beautiful specimen plants.

OUT & ABOUT

I am busy getting potted plants, containers etc. ready for my exhibits at our local Hort. Society’s annual show on Tuesday, Aug. 20, from 2 to 7 p.m. at the Minnedosa Community Conference Center on North Main Street.

This year the Minnedosa Horticultural Society is celebrating its 100th birthday so we are serving birthday cake and rhubarb punch from 2 to 4 p.m. Come help us celebrate!

Albert Parsons is a consultant for garden design and landscaping who lives in Minnedosa.

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