Taking an environmentally sensitive approach to pest management
Late-summer into early fall is a period when the fruits of many plants in the wild begin to mature. Unfortunately, it also is a period when plant poisonings tend to be more prevalent. Children are the most common victims because of their tendency to explore their world through the sense of taste, as well as through sight. Therefore, it is important to warn children not to pick or eat fruits or berries from plants they do not know. Children considered too young to understand should be kept under close supervision and away from any plant that might present a potential danger to them.
Most plants grown in the home landscape present little or no danger from berry poisoning. However, there are a number of wild plants that should be avoided. On rare occasions, these plants accidentally find their way into the home landscape via the activity of birds or other animals that disseminate their seeds.
Even though most berries are not highly poisonous, children who ingest them may become ill. The latter depends on the type of berry and the quantity consumed. Most toxic compounds are rated in toxicity according to the amount that must be ingested per unit of body weight to produce an effect (i.e. mg active ingredient/kg body weight). Since children weigh less than adults it takes less of a toxic compound to produce visible symptoms of poisonings in children than in adults.
One of the most easily misidentified toxic berries is the fruit of a wild vine called moonseed (Menispermum canadense). The common name of the plant is derived from the fact its seeds are shaped like a crescent moon. The leaves of moonseed are shaped somewhat like those of wild grape. Additionally, the plant produces small bunches of bluish-black berries in grape-like clusters. Fortunately, although moonseed berries resemble wild grapes in appearance, they have a taste which has been described as “rank”. Another identifying characteristic is that moonseed produces one single, large seed per berry, whereas wild grape produces several small seeds ovoid in shape.
A common wild plant that produces berries that are quite toxic is black nightshade (Solanum nigrum). This annual often is found in areas where there is little competition from other plants, since it needs bright light to flourish. The plant produces small white flowers that are shaped like those of tomato, to which it is related. The leaves of black nightshade are somewhat triangular-to-ovate in shape and coarsely toothed with wavy margins. In late summer, black nightshade produces small clusters of dark purple berries in its leaf axils that contain a glycoalkaloid toxin known as solanine. The toxin is most concentrated in unripe, green berries of the plant which, reportedly, have caused fatalities. Ripe berries are less toxic but still should be avoided.
Horse nettle (Solanum carolinense) is not a true nettle but rather is related to members of the nightshade family Also known as bull nettle, it has irregularly-lobed, coarsely-toothed leaves covered with fine hair, and a stem that bears spines. Very common along roadsides and in pastures, horse nettle bears small fruits that resemble miniature tomatoes that turn golden yellow when fully mature. Although only modestly toxic, all parts of the plant should be avoided and children should be warned against picking its colorful berries.
Pokeweed (Phytolacca Americana) is another plant that produces tempting purple berries in late summer and fall. Although there are those who use this plant in early spring as wild greens, this practice cannot be recommended because of the plant’s toxicity. Reportedly, adults have died from eating improperly prepared poke greens. The toxicity of pokeweed increases in intensity as the plant matures, with the stem and roots being the most toxic part of the plant. Although the colorful purple berries contain less toxin than the remainder of the plant, they still are considered poisonous and should be avoided. Pokeweed is often spread by birds who favor the berries as a food source but are unaffected by its toxic component.
A few plants have seeds that are toxic rather than berries. Several members of the genus Aesculus fall into this category. Ohio buckeye (Aesculus glabra) is a good example. It is a small tree of the woods and landscape that produces large shiny, dark brown seeds. Although buckeye seeds would be difficult to eat because of their hard seed coat, they are considered poisonous when eaten raw by either people or animals and should be avoided.
Finally, castor bean (Ricinus communis) is a large, herbaceous plant with attractive, palmately-lobed leaves. It has considerable horticulture merit as a landscape plant when used for shade or a screen, and several named cultivars have been selected from the species. Castor bean bears shiny, bean-like seeds that contain ricin, one of the most toxic substances found in nature. It has been suggested that one seed contains enough ricin to kill an average adult. Castor bean should not be planted in landscapes frequented by small children. For other areas, removing the blooms as they develop to keep seeds from forming would be a wise precautionary measure.
The rationale behind consuming plants from the wild has always escaped me, since we have such an abundance of cultivated food to eat. However, for those who enjoy “living off the land”, a positive identification of any wild plant is very important before any seeds, berries or fruits are consumed. The adage: “When it doubt, throw it out” lends itself well to the prevention of accidental poisonings. Our ancestors spend thousands of years selecting fruits, berries and others food sources from plants largely through trial and error. Sticking with the “tried-and-proven” will avoid accidental poisonings and the human suffering that comes with it.
Disclaimer: The preceding article was written for educational purposes only. Please contact a physician or the nationwide poison information center (800-222-1222) if you suspect someone has eaten a poisonous plant.
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REVISED: August 15, 2016