Tovah Martin laments the “Trojan horses” that have invaded her garden

AMAZINGLY, I DON’T HAVE goutweed yet—knock on wood. I have everything else that could possibly be caught from other gardeners. I wage a constant battle against bugleweed, plume poppy, violas, bee balm, spearmint, Japanese anemones, perennial cornflowers, and gooseneck loosestrife—to mention only a wheelbarrowful of the primary offenders. But so far, no one has infected my garden with goutweed (Aegopodium podagraria). It’ll come.

The problem is, gardeners are generous. Go to visit a garden, and chances are that you won’t come home empty-handed. You need do nothing more than cast a compliment in the general direction of an iris, and a clump is probably destined to accompany you home. Which is fine, if all you return home with is the iris. But in my experience, a hitchhiker often comes along for the ride.

It can be worth it. A few autumns ago, a friend called to say that she was transplanting her garden and had an overabundance of herbaceous peonies to juggle. Did I want some? The tire marks still testify to the speed at which I made tracks over to her place. The peonies are in my garden now. They’re mature, they’re gorgeous, they’re heirloom varieties, and I love them, but they came with a lot of baggage. That’s when the battle with the Japanese anemone began.

The problem lies in the ability of some plants to spread with amazing speed aided by underground runners. Often, only a tiny segment of root matter is needed to give them a foothold in your garden, and then off they go, sending roots far and near. Once a plume poppy becomes established, you’ll be pulling up plume poppies for the rest of your gardening career. And whoever inherits your property will be shaking their fist and cursing the day you let the plant into your life.

Of course, you could just say no. Some gardeners avoid the issue by refusing any freebie that’s offered. After all, if a gardener has a surfeit of echinacea or phlox, chances are that plant does some fast footwork. Of course, that’s not always the case—a lot of perennials require dividing on a regular basis and, if you’re lucky enough to show up at dividing time you might be the fortunate recipient of something rare and wonderful. Then again, you could be welcoming a Trojan horse that refuses to remain contained.

What’s the solution, assuming you can’t resist a free rarity offered by a fellow gardener? Take those peonies. If I’d had any sense whatsoever, I would’ve shaken off all the soil from the peony roots rather than trying to transplant them with as large a rootball as possible. That’s where all those unwanted stowaways were hidden. Now, I keep a vigilant watch on what happens around all new transplants for the first couple of seasons. If I can catch an invader early, before it has sent runners hither and yon, I know I’ll be less likely to be haunted forevermore.

Of course, not all troublemakers travel incognito. Sometimes you unwittingly create your own nightmares by craving a plant that will eventually muscle out its neighbors. One year I ordered half a dozen meadowsweet (Filipendula ulmaria) to form a lacy backdrop for a garden. But when I picked up the plants and saw the thick rhizomes curled around and around the container, just bursting to be set free, I decided to plant them elsewhere. As a rule, I don’t put anything with crawling rhizomes into my closeknit perennial borders—roving characters go into a bed of their own where they won’t be a menace to their neighbors.

As far as passing along problems, I try to be conscientious. I’ll dig on demand when other gardeners crave something from my garden, but I never share without a disclaimer. I warn against what might be happening underground. Unless you were the one who gave me the plume poppy…Share and share alike. H

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