by Karen Weiland, Advanced Master Gardener
Lilacs are known for what is called “sucker growth”. This is when the plant sprouts new growth from the root system. Some varieties are more prone to this than others, so to minimize suckering, choose varieties that generally sucker less. Do some research before making your purchase.
Generally, most trees and shrubs have the capability to suckering. When they are healthy, most trees and shrubs will sucker very little. When faced with some kind of stress, however, their response will be to send out suckers. Planting a tree or shrub too deep, a very common mistake, can cause a plant to sucker. Do not prune too much. Taking more than one third of the plants’ top growth can trigger the sucker response. When you take too much “green” from the plant it cannot make enough food for the root system. It will want to try to replace what it has lost. Prolonged drought, disease and pest infestation, anything that makes a plant think it is dying, can make it produce suckers if it is prone to that.
On grafted plants, it is important to control suckers. Suckers from below the graft union are growing from the rootstock, which is a different type of plant from what you bought and want to grow. A rootstock is often times a very vigorous type of plant and its sucker can grow fast and take over the plant you meant to grow.
Tearing, rather than cutting the sucker rips out the basal dormant buds that would otherwise be left behind to form new suckers. Put on some gardening gloves, get a good grip on that sucker and give it a yank. Don’t let the sucker get too big. The earlier you do it, the easier it will be to remove it. If a sucker has been allowed to live for several weeks, it may have grown to big to be easily torn off so a loper or pruner may be needed to remove it.
Have you ever taken down a tree that keeps on sending up suckers from the remaining root system? Suckers from underground roots will tend to keep on growing as long as the root system has food and of course that food comes from those new shoots. Removing the entire root system is the best answer to keep those suckers from coming back but it is not the most practical. No one wants a huge section of their yard ripped up to remove a root system. About the only thing you can do is to continually keep tearing off the suckers so they can’t make food. Remove them as soon as you see them so they cannot send food to the roots and eventually the roots will “run out of gas” and die off. This process can take up to 2 years. The active ingredient in Round-Up is glyphosate, a non-selective trans-locatable herbicide. You can use this on suckers, however, if they are located in your lawn, your grass will die too. Also do not use Round-up on suckers growing from trees and bushes as this will kill that tree or bush too.
Of course there are exceptions to every rule and there are instances where you may want a plant to spread. Planting a series of suckering bushes, over time, can form into a privacy hedge, screen or barrier. These kinds of plants also do well in a naturalized or “wild” area. In an area that has a steep hill, a suckering shrub may be a low maintenance, beautiful answer. With some plants you just have to expect them to try to spread over time and accept it or make controlling them a part of your gardening maintenance chore.
As always, Happy Gardening!
More information about gardening and related subjects is available online at www.hort.purdue.edu/est/garden_pubs The Purdue University Cooperative Extension Service can be reached at 499-6334 in LaGrange Co., 636-2111 in Noble Co., 925-2562 in DeKalb Co., and 668-1000 in Steuben Co.
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