Gardening Advice: Toxic Plants and Perennial Weeds

Toxic plants and perennial weeds can be sneaky garden foes. Learn how to battle them and win with advice from Teri Dunn Chace.
By Teri Dunn Chace
May 2012
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“The Anxious Gardener’s Book of Answers” by Teri Dunn Chace identifies the 100 most common gardening mistakes and gives you the information you need so that you’ll never make them. Or, if you’ve already goofed, it tells you how to fix the mistake.
Courtesy Timber Press

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Your garden is supposed to be fun — a place to relax in and recharge your batteries, a source of beauty and pleasure. But all too often, things go wrong. Those expensive tulip bulbs you planted last fall never came up. Your lilac doesn’t bloom. The lawn looks terrible. And worst of all, you don’t know what to do about it. The Anxious Gardener’s Book of Answers (Timber Press, 2012) contains great gardening advice to help you solve virtually any gardening challenge. In this excerpt from the chapter “Weeds and Problem Plants,” author Terri Dunn Chace provides advice for dealing with two garden snafus: growing toxic plants and letting perennial weeds take hold. 

Growing toxic plants

Some garden plants are poisonous. Garden centers don’t always post warnings, so you might have no way of knowing a plant is toxic until someone falls sick. While it’s rare for a child or pet to eat leaves, berries, seedpods, or roots, it can happen, and the worst-case scenario is grim.

Among the common toxic plants that should never be ingested are rhubarb (very poisonous leaves), larkspur (seedlings as well as seeds), monkshood (roots), irises (rhizomes), daphne (berries), castor bean (even one seed can be lethal), yew (berries and needles), oleander (leaves, stems), daffodils (bulbs), and all parts of rhododendrons, azaleas, and cherry laurels. Symptoms vary depending on the plant and the size of the person or animal ingesting it, but they can range from digestive upset to irregular heartbeat to fatal seizures.

The right way to do it: If small children or unleashed pets frequently visit your yard, err on the side of caution and supervise them at all times. Lecture children from the time they can understand to never, ever ingest anything in the garden. Never let them see you sampling anything, which could awaken their curiosity or give them a false sense of security.

When shopping for plants, inquire about their safety or look it up yourself. If you choose something that is potentially harmful, block direct access to it with other plants or garden decor (plant in the back of a flowerbed), trim off low branches, or even post a warning sign.

If I goofed, can I fix it? Chances are if a child or pet manages to consume and get sick from a daffodil bulb or the yew bush in your yard, you’ll be inclined to tear it out and replace it with something safe. If you opt to keep it, employ at least one of the safety measures described.

If you ever suspect poisoning, immediately call for help—911 for a person, and the nearest vet for a pet. (Find a list of plants toxic to pets at ASPCA: Toxic and Non-Toxic Plants.) Also, be sure to get a sample of the plant you suspect caused the problem; anyone treating the afflicted person or animal will want it.

Letting perennial weeds take hold

Not all weeds are created equal, and perennial weeds can be daunting adversaries once they get a foothold in your yard and garden. Even if you are watchful and cut them down with a hoe, like you do with sprouting annual weeds, they can still get the upper hand. Generally speaking, their main modes of reproduction are their root systems (ground ivy) and prolific production of runners (quack grass). When you try to dig them up, if you leave any portion of root or runner behind, they can and will return. Tilling an affected area can actually make the weed problem worse by distributing chopped-up bits throughout the bed, each capable of regenerating. It sounds like a science-fiction nightmare, but it is all too real.

The right way to do it: First, to correctly identify a weed as a perennial type, look it up or show a sample to someone knowledgeable. Or simply take your cue from the fact that your enemy clearly has extensive, deep, vigorous root systems.

Ideally, start combating perennial weeds when they are still small in size and number. Mulch thickly or cover a bed with plastic. For weeds that get through these barriers, go after them with a sharp hoe or by hand pulling or spot treating with an herbicide. Do not till or hoe deeply, and work to extract the entire root system (which is much more easily accomplished when the ground is damp). A garden fork is a better tool for digging out extended plants (a shovel or trowel tends to just break the roots).

If I goofed, can I fix it? Once you have identified their presence, do not allow perennial weeds to spread, or the problem will only get worse. In moderate cases, apply diligent, consistent combat as described. Depending on which weed you are fighting and how much of a foothold it has, confine yourself to growing only annuals (flowers or vegetables) in the affected area until you beat back the invader. Battling perennial weeds among perennial plants is logistically daunting. With severe infestations, you may have to remove all desirable plants in the area, no matter what they are, and then get to work and fight until you prevail.

This excerpt has been reprinted with permission from The Anxious Gardener’s Book of Answers, published by Timber Press, 2012. 

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