Learn How to Battle the Suckers in Your Garden

Suckers Can Swallow Up Your Plant; Pruning Controls Them

Big cedar tree
sbeebee/Flickr/CC BY 2.0

Here’s something that almost every gardener with a tree or large shrub is bound to deal with: the sucker. This cheerful name described very vigorous stem growth coming from a plant’s root system but some distance away from the crown. You need to recognize and learn how to deal with suckers to preserve your plant’s health at the least, its good looks often as well, and in some important cases, the very stability of its identity!

If that piqued your interest, read on and find out how a couple of times a year you might need to prune out or rip off those nasty suckers before they turn your plant into something you don’t want.

What Is a Sucker?

When a root sends up a new stem away from the main stem, we call it a sucker. Suckers are also any new vertical growth that arises from the base of a trunk. On a grafted plant, anything that grows vigorously below the graft union can be called a sucker. 

Picture asparagus. You can recognize suckers by their fast growth and usually long internodes, long and weak wooded. Often clusters of many suckers will arise from a single point. Think of asparagus growing: asparagus is a suckering plant whose suckers we cut down and eat.

I love asparagus, but on almost all trees and many landscape shrubs, suckers are generally unwanted. They’re sort of like parasitic rebels. Even if distant from the original plant, the new stem is connected to the main trunk or crown of the plant by the roots underground, sharing its food and water, though from above ground it looks like a separate plant from the parent. Suckers are very similar, by the way, to watersprouts, which are the same kind of youthful, rampant, vertical, generally unwanted growth, but from a branch rather than from a root.

Suckers are like a new baby plant that has suddenly come into being connected to the relatively massive root system of its older parent: in short, it is young, vigorous, and has a lot of food. For this reason, suckers are able to grow very, very fast, easily many feet in a single season. They are your toddler outgrowing pairs of shoes. Your teenager stealing the credit card and going on a spree. Suckers are ravenous nuisances.

Why Do Suckers Form?

Plants are different from most animals in that under the right conditions, almost any part of a plant can create any other part of the plant. Your finger can’t grow an eyeball and your bones can’t grow blood vessels, but plants actually can do things like this. The veins of a leaf pinned to moist soil can often grow roots. And roots, even a piece of a root, can almost always grow new stems, which then can grow all other parts. This ability lets us propagate plants to make new ones, but it’s also how suckers happen.

Normally hormones from the growing tips of plants prevent wrong parts of the plant lower down from growing. Harm to the growing tip that produces the hormones, or to the tissues in between that transport the hormones, makes suckers much more likely. They can also happen to very healthy plants, or to plants of certain species very prone to suckering (not necessarily a bad thing to do in the wild).

Why Are Suckers a Problem?

As I said above, a sucker grows very quickly. Isn’t this a good thing? Usually, no. Here are the main reasons: 

  • Suckers are in the wrong place. A sucker is directing energy towards the growth of stems where you probably don’t want them. Little stems growing in the shade of a large shade tree look strange. New shrubs near your old shrubs might ruin the effect of your planned grouping, especially if you are the more controlling kind of gardener. 
  • Suckers rob energy from the main plant. On a large tree, the energy loss is not a big deal. On smaller plants, the loss can reduce your flower or fruit set. On grafted plants, the robbing of energy is devastating, and a special case.
  • The worst case: in grafted plants, suckers from the rootstocks devastate and take over the plant. When you have a grafted plant, this is the most important case to remove suckers. In these cases, suckers are of a different variety from the plant you purchased. It is likely to grow much faster than your variety and overtake it, sometimes literally engulf it, creating a “new” plant that will not be the one you wanted.

A lot of woody plants you buy in the nursery are grafted onto rootstocks of a different variety or species from the one you bought, and nurseries never tell you this. For this reason, it’s a decent idea to assume suckers are a problem unless you know otherwise. If the sucker has leaves or flowers that look different from the main plant, you know you have a rootstock renegade.

How to Deal With Suckers

Depending on your plant and your needs, you’ll need to know how to deal with suckers in a variety of ways. Usually, you’ll want to cut them off just as you’d expect. Sometimes you’ll need to rip them out by hand! Sometimes, in cases like those covered below, you might want to leave them right where they are, or transplant them.

When Are Suckers Not a Problem?

There are exceptions to every rule. On the right plants in the right garden, suckers are an opportunity. 

  • Forming a naturalized or wild-like area. There are a lot of plants that naturally clone themselves by suckering, sometimes to a massive degree over time. If your garden has the space and you like the wilder look that you get when you let suckering take its course, hey, go for it. It’s mostly advisable on plants that look good in wild masses. It’s never a good idea with grafted plants. 
  • Reproducing, or propagating, your plants. If your plant is not a grafted plant, you can dig up its suckers and replant them elsewhere. They are very likely to live and grow into new plants. You can also cut suckers to use as scions, as though from a stool bed.