Wild parsnip: An edible root with poisonous sap
Often referred to as poison parsnip, wild parsnip (Pastinaca sativa) is a biennial plant, native to Asia and Europe. It’s widely accepted that wild parsnip plants are actually descended from cultivated parsnips brought to North America by the European colonists. Documents suggest that cultivated parsnips were grown in Virginia as early as 1609.
Over time, the plants have reverted back to a wild strain. The wild genes were always there, but they remained suppressed until eventually being displayed through natural selection. The edible first year taproots are genetically identical to the vitamin-C-rich parsnips we plant in our gardens. There are significant differences however, in the biochemical properties of cultivated versus wild parsnip.
Today, wild parsnip is considered an invasive member of the carrot family — related to Queen Anne’s lace — that has become naturalized across most of the United States and Canada.
Harmful to the environment
Wild parsnip grows in sunny areas and tolerates almost all soil types. It tends to colonize disturbed areas and spread voraciously, reducing habitat for wildlife and insects by displacing the native vegetation species that provides food and cover and that would otherwise thrive in similar growing conditions.
It’s often found along highways and railroad tracks or bordering farmed fields. But it can also become established in pastures and abandoned fields. It’s aggressive and spreads by seed.
It seems to me that wild parsnip is more prevalent this year than in previous years. Noticeably high plant-densities may be the result of particularly favorable conditions. But the seeds may also have been very-effectively spread by mowing equipment. The mature plants that are currently present in roadside landscapes, if not in seed now, will be in seed, soon.
A threat to human and animal health
If you stumble upon wild parsnip unknowingly, the results can be debilitating. The sap of wild parsnip plants can be toxic, or more accurately, “phytophototoxic” to humans and animals. Hence the nickname “poison.” Contact with the sap greatly increases the sensitivity of skin to ultraviolet light. Should you get the sap on your skin, it will reduce your skin’s defense against exposure to UV rays.
In other words, the sap of wild parsnip can cause skin, when exposed to sunlight, to (sun)burn horrifically, resulting in discoloration, intense burning, terrible rashes, and festering blisters, a condition known as a “phytophotodermatitis.” The burns may take weeks, or even months to heal, and may leave permanent scarring. And if sap gets in your eyes, it may result in blindness.
It’s important to emphasize that you can’t get burned by just brushing up against wild parsnip. A stem or leaf must be broken, exposing skin to the sap.
If ingested, livestock (or people) will likely experience mouth pain and oral dermatitis.
Should the toxins enter the bloodstream, burns will appear on the animals’ skin. Because of this, poison parsnip needs to be managed in pastures.
Lifecycle of wild parsnip
Wild Parsnip is a biennial. Low-growing clusters of compound leaves (rosettes) ranging from 5 to 15 inches form during the first year, but not the tall stem. Instead, all of the plant’s energy goes into developing the thick, fleshy, edible (when roasted) taproot. During the second year, the plant grows tall. After the flower produces seeds, it dies.
Wild parsnip emerges in spring. Seedlings have small, ovate leaves on long petioles (stalks that attach the leaf blades to the stems). The seedling leaves are toothed and are a yellowish-green color.
Later leaves are compound, meaning the leaves have a central stem with three to five toothed, somewhat-diamond-shaped leaflets coming off of them. Leaves vary widely in size. Lower leaves have short stems, while leaves higher on the stalk have no stem.
The vertically-grooved stalks are hollow throughout, except at the nodes.
In the flowering stage, wild parsnip can grow to be 6 feet tall. The stalks will be topped with umbels; umbrella-like clusters of small yellow flowers. Each tiny flower in the umbel has five petals. Plants produce 1/4-inch-long, oval-shaped seeds. The seeds are bright green at first, but as they mature, they turn brown. A single plant can produce up to 1,000 seeds, all of which can survive in the soil for up to four years. Plants will often have both flowers and seed at the same time.
Control of wild parsnip requires particular care. Elimination of seed production and spread is the goal. Prevention is the best control method.
When wild parsnip is first detected, it can be pulled or cut below ground level with a sharp shovel. Be sure to wear protective clothing (long sleeves, long pants, gloves, boots, and eyewear) and try to work after sunset, in order to avoid exposure to sunlight.
If populations are fairly large, you can mow or use a brush-cutter after the plants bloom, but before they set seed. Remove the cut material. You may have to repeat the treatment in two or three weeks to prevent plants from re-sprouting.
Once poison parsnip is established, there’s a seed bank in the soil, so new plants will likely continue to emerge for several years.
Never use a string trimmer to control wild parsnip.