Poison hemlock (Conium maculatum) is a highly toxic, invasive plant species that is found in Victoria, BC, as well as other parts of North America and Europe. It is a member of the Apiaceae family, which includes other common plants such as carrots and parsley. However, poison hemlock contains potent alkaloids, including coniine and gamma-coniceine, which can be fatal if ingested.
The plant can grow up to 2-3 meters in height, with a hollow, purple-spotted stem and delicate, fern-like leaves. It produces small white flowers in umbrella-shaped clusters from May to July, which can be a distinguishing feature when identifying the plant.
Poison hemlock is often found growing in disturbed areas such as roadsides, waste areas, and abandoned fields. It is a prolific seed producer, which allows it to spread quickly and outcompete native plant species. It can also be spread through the movement of soil, equipment, and animals, making it difficult to control once established.
Due to its toxic nature and ability to outcompete native vegetation, poison hemlock is considered a serious invasive species in Victoria, BC, and efforts are being made to control its spread. The City of Victoria has developed a management plan for the species, which includes strategies such as manual removal, herbicide application, and education and outreach to prevent further spread.
How to Identify Poison Hemlock
Poison hemlock goes by many names, names such as California fern, poison parsley, or deadly hemlock.
Hemlock is nearly a dead ringer (pun intended) for yarrow and Queen Anne’s Lace – wild carrots. The similarity between both the flowers and the leaves between these beneficial weeds and poison hemlock is why novice foragers are staunchly discouraged from plucking them from the fields and forest edges where they thrive.
During its first year of growth, poison hemlock forms into a rosette and is in what is often called the “vegetable” stage. It is a biennial and doesn’t flower until the lethal weed is in its second year of growth.
Poison hemlock plants typically range in height from three to eight feet tall, but have been known to grow as high as 12 feet.
Each flower on the poison hemlock plants grows into a densely ridged fruit that houses multiple seeds, and is green in color.
Once the toxic weed matures, the fruit on the flowers turn a shade of grayish brown.
During its second year of growth, the poison hemlock plant grows tall stems and ultimately flowers.
Unlike wild carrots and yarrow, the stems of poison hemlock look as if they have been splattered by purple paint. The amount of purple blotching can range in both coverage level and hue.
The stem of a poison hemlock plant is also thicker than that of Queen Anne’s Lace and yarrow.
Stems on the lethal weed are hairless and smooth and rather glossy.
The leaves on the plant throughout its stages are feathery and can appear to look like fern leaves.
Poison hemlock also smells plain awful, like a pile of musty debris. Some researchers maintain it stinks like mouse urine – especially when the leaves of the weed have been crushed.
The leaves on the plant can look bluish-green in color and are three to four times pinnately compound.
Poison hemlock leaves also have deeply cut or parsley-like leaflets with fairly sharp-looking points.
Symptoms of Poison Hemlock Poisoning
Slowed heartbeat – weak pulse
Central nervous system paralysis
Loss of coordination
…and it could even result in a coma!
Poison Hemlock Management
Getting rid of poison hemlock is NOT easy. The best time to cut it down is during the early spring before it has bloomed – and then go to work on the roots.
Never, ever, use a weed eater to remove poison hemlock, all of the movement that causes can jiggle the flowers enough to release the toxin – and cause it to be ingested via the eyes and nose of the person attempting to get rid of it.
If the noxious weed is still small, digging it up to eliminate both the root and the plant at the same time is recommended. If the plant is mature or close to maturity, cutting it out using a machete is typically the best action to take.
Never burn the plant after removing it. This will release the toxins into the air – potentially allowing them to infiltrate the eyes, nose, or even the mouth of any person or animal in the immediate vicinity.
Always wear thick rubber gloves, long sleeves, and long pants when removing poison hemlock. Cover the mouth with a medical mask or bandana, and wear protective eye gear to protect those facial features, as well.
Many websites and researchers recommend using chemical products like Monsanto’s RoundupReady ready with glyphosate and similar products that contain the 2,4-D compound to get rid of poison hemlock.