Suckers can be a nightmare for vulnerable plants and if not controlled will completely take over, so the best thing to do is act immediately even if this means taking out the full root, advises PETER CUNDALL
Act now to ensure everything will come up roses
Many grafted trees and shrubs are prone to sending up lots of useless but powerful suckers. They are different from normal, vigorously healthy shoots because all sprout from below grafting unions, emerging from root stock on to which many trees and roses are grafted.
Suckers commonly appear around fruit trees, especially plum, apple and some citrus varieties.
Other trees may appear to produce suckers, even forming thickets of vigorous stems, particularly hazelnut, fig and mulberry varieties. However, these trees are either propagated from cuttings or in the case of hazels, from divisions, so these worrying ‘suckers’ are normal healthy growth.
Suckers can be a nightmare with vulnerable plants and if not controlled will completely take over, dominating and stunting growth grafted on to them. Although root stocks are related to scions, they always look slightly odd and always produce alien blooms, inferior fruit or differently shaped, pale-coloured leaves.
There are several reasons why grafted plants sucker. The most common is
Right now suckers are in full, active growth and are just beginning to store carbohydrates to give them a flying start
damage to lower bark or roots before or after planting. Rose bushes are a typical examples. Often when planting new, bare-rooted plants in winter, bright green sucker buds can often be spotted on or near damaged roots. These should be immediately cut out, even if means taking out the full root.
All rose bushes and climbers have a tendency to become top-heavy. That’s why even the smallest, stick-like new plants must be firmly staked and secured right from the start. When wind causes unsupported plants to rock to and fro, roots are torn, making sucker growth inevitable.
The worst examples of roses suckering can usually be found in gardens where the soil around the plants are regularly cultivated. This type of thoughtless digging disrupts root systems, weakening plants and stimulating forests of palegreen, thorny suckers.
One way to remove and control rose suckers is to grasp stems firmly with gloved hands and forcibly drag them from
the ground, always pulling away from plants. However, with young roses, there’s always a danger of pulling entire plants rose from the ground, roots and all.
I prefer to insert a sharp spade just the inside each sucker then slice downward, cutting cleanly through offending roots before dragging them out.
This control is best carried out in summer when plants are in active growth. While it cannot put an end to serious sucker problems it is more effective than doing the job in winter.
Rose plants grown from cuttings cannot sucker because they are not grafted. However, while relatively slow to become established, they have a far longer life than grafted plants. Some of the oldest climbing and bush roses in Australia have been growing for over a century and all are on their own roots.
The most conspicuous suckers emerge from the standards of weeping trees. These trees cost a lot because many have two or more scions inserted, sometimes up to two metres above the ground. The long-stemmed root stock can take several years of training to fully develop.
When tufts of weird-looking growth emerge halfway up the stems of weeping standard trees or worse still, powerful shoots that, instead of drooping, reach for the sky, they are suckers. Cut them off flush with trunks and don’t leave stubs.
Right now suckers are in full, active growth and are just beginning to store carbohydrates to give them a flying start in spring, even after a savage winter pruning. Cutting them out now massively reduces the amount of stored energy they can accumulate, drastically weakening spring growth.
Many established lilac trees still growing in old gardens were originally grafted on to closely-related privet stock which is notorious for suckering. In the past I was often asked to investigate why old lilacs had stopped flowering, usually to discover enormous privet suckers totally surrounding a tiny, half-dead and completely suppressed lilac.
These days most lilacs are grafted on to either seedling lilacs or Japanese tree lilacs. Even so, when newly-purchased are planted – preferably bare-rooted in winter – the planting holes a dug extra-deep. This ensures that the graft union is also buried allowing scion-wood to develop its own roots above the graft.
Eventually the ‘nurse; roots down below wither away and the plants finish up on their own roots, eliminating any danger of suckers appearing.