My garden is full of them. Suckering shrubs — Oregon Grape (Mahonia aquifolium), Snowberry (Symphoricarpus albus), and common Lilac (Syringa vulgaris) — the last now in glorious bloom. There’s a suckering tree as well — the dreaded Tree of Heaven (Ailanthus altissima), known around here as the Tree from Hell.
The standard advice for dealing with suckers is to trace each one back to its point of origin on the parent shrub and tear, not cut it off. Tearing has a lasting effect, apparently (similar to plucking rather than shaving unwanted hair). Remove soil if necessary to accomplish this, the advice says, helpfully. Well, that’s fine if the shrub and its suckers live in solitary splendour with nothing around them except grass, possibly, but what do you do when the shrub is surrounded by perennials, bulbs, groundcovers, and even other shrubs? “Removing soil,” otherwise known as digging, isn’t really an option in a densely-planted mixed border, especially if a multitude of suckers has popped up several feet away from the parent plant.
The best advice is don’t plant sucker-prone shrubs to start with, no matter what other qualities they possess. So what if they’re native plants? Both Mahonia aquifolium and Symphoricarpus albus are native to my region, adapted to local conditions and trouble-free. They settled in happily here, sending up shoots with enthusiasm over the years. If I had several acres at my disposal and wanted a natural garden that could be left to its own devices, these plants would be great, but on a 50 x 120 foot lot (that also accommodates a house, garage, driveway and paved walks), planting these and other suckering shrubs guarantees either a wilderness effect or a gardener ready to nuke everything with herbicides and start over again. (I wish I could go back in time and give my younger self this lecture).
So — with the “nuclear” option not practicable, and not being ready to move to another patch of land, what do I do about suckers (besides curse and wail)?
In theory, it would be good to create a cordon sanitaire around sucker-prone shrubs, clearly defining a no-go area for each one. No suckers beyond this point! This would be done with a sharp spade, plunged into the ground all around the offending shrubs, at a distance of several feet. The process would have to be repeated at least twice a year, similar to edging a bed or border. Given the brutality and intensity of the work, there could be no plants of value growing in this foot-wide space. But setting a border makes the situation seem less chaotic and limits the space in which sucker removal is absolutely necessary.
Any suckers detected outside the cordon sanitaire would (in theory, at least) be removed immediately using minimally invasive techniques. First, the good old yank-by-hand method. Sometimes it works. More often than not, the sucker snaps at ground level, leaving a stump that’s hard to hold on to. Or the bark strips off, resulting in a little whip that’s too slippery to yank. A tool is then needed. For small young suckers, a dandelion tool works. Thrust it parallel to the sucker until it cuts and the sucker releases. (But remember, cutting isn’t as effective as ripping). For older, thicker suckers, a small, cheap, pointed saw of a type designed to cut gyprock (sheetrock) works fairly well. Like the cutting-with-spade procedure, this search and destroy operation is best repeated at least twice a year. Three or four times is better, especially in regions with mild winters. Constant vigilance is best.
I have a fleeting hope that if I follow these processes diligently, the shrub will get the message, “None of your suckers will live to see the light of day!” and stop sending out the roots from which suckers grow. But somehow I doubt that will be the case.
In reality, the years have a way of slipping by, and the gardener is not as diligent as necessary. In my garden, it’s too late for the cordon sanitaire. Roots of Oregon grape and snowberry have spread far and wide. For the past several days I’ve been engaged in an epic struggle with an enormous Oregon Grape (Mahonia aquifolium). I removed three large stems (diameter 2-4 inches at the base) and reduced the remaining plant’s height from about 12 feet to 8. Worst of all was pulling, digging or cutting (sometimes all three) a multitude of suckers, ranging in size from less than a foot tall and 1/4 inch in diameter to 4 feet and 1 inch diameter.
I cherish no illusions that the suckers are really gone. Their stubs and deeply buried roots are still there. They will no doubt rise again, like a bunch of prickly green zombies. Really, the best way to avoid suckers is not to plant suckering shrubs. And if any plant shows suckering tendencies, rip it out.