Wild plants: are they edible or poisonous?
Never collect plants from a roadside because of possible contamination with automobile emissions. Avoid harvesting plants from areas where pesticides might have been applied. Don't harvest plants or plant parts on private property without first obtaining permission and be aware of regulations prohibiting plant harvesting in city, provincial and federal parks.
It is essential to identify plants to the species level before using them as food because toxic and edible species may differ very little. For example, water hemlock, Cicuta maculata, and other Cicuta species, which are the most violently toxic plants in the Northern Hemisphere, can easily be confused with other similar appearing members of the Umbelliferae (Carrot/ Parsley family) such as water-parsnip (Slum suave). It is best to avoid all plants in the Urnbelliferae family as a mistake in identification could be deadly. Another example is Sambucus canadensis, the purple-fruited elderberry, with edible fruit, and Sambucus racemosa (red elderberry), the only species found wild in Western Canada, which has poisonous fruit.
Sometimes, colour is a clue to edible fruit. Honeysuckles (Lonicera spp.) that have red or yellow fruit are poisonous, but species such as Lonicera caerulea, which have blue-coloured fruit, are reported to be edible. It is advisable to avoid plants with whitish fruit. The best known example is poison ivy (Toxicodendron radicans, formerly Rhus radicans), where the fruit as well as the rest of the plant causes severe allergic skin reactions for many people. The fruit of Rhus glabra (smooth sumac) can be used to make a lemonade-type drink. However, persons who are very sensitive to poison ivy may also develop a skin reaction to smooth sumac. The white berries of Symphoricarpos albus (snowberry) are poisonous, as are the white or red berries of Actaea rubra (baneberry). Many plants with a milky sap are not edible, including milkweed (Asclepias spp.), spurge (Euphorbia spp.) and dogbane (Apocynum spp.).
The leaves and flowers of violet (Viola spp.) are reported to be edible, but actually only the species that have blue flowers should be eaten. Eating the leaves or flowers of violet species with yellow flowers can cause violent stomach upsets.
Some edible wild plants, such as dandelion greens and water lily rhizomes, are bitter, making them unpalatable. Boiling the leaves and roots in several changes of water will usually remove these bitter properties. The acorns of oak (Quercus spp.) contain toxic levels of tannins. The tannins can be leached out with successive boilings in water, but unless one is in desperate need of the acorns as food it is probably not worth the effort.
It is important to obtain information on what parts of a particular wild plant are edible and how to prepare them. Just because a certain plant is listed as edible, it is not necessarily palatable. Many plants have both edible and poisonous parts. An example is chokecherry (Prunus virginiana); the fruit is edible, but the seeds, leaves and bark are poisonous. An 'almond' scent or taste in woody parts and leaves of Malus (apple) and Prunus species (plum, pincherry, sandcherry and chokecherry) is an indication of toxic levels of cyanide compounds. The fruit of these same plants is edible.
Some wild plants are edible raw, but others are unpalatable or even poisonous unless cooked or otherwise processed. The young leaves and unopened flower buds of marsh marigold (Calthapalustris) are poisonous when raw, but can be eaten when cooked, but only with extreme caution. Mature leaves are poisonous even after cooking. Some wild plants have high concentrations of oxalate compounds. Oxalates produce a sharp burning sensation in your mouth and throat and can damage the kidneys. Examples are plants of the buckwheat family such as dock (Rumex spp.), and garden rhubarb (Rheum officinale). The stems of rhubarb are edible, but the leaves contain toxic levels of oxalates. Many plants are edible only at certain times of the year. Dandelion greens are edible when young early in the season before the plants flower, but mature leaves are very bitter. Newly emerged shoots of stinging nettle (Urtica dioica) and wood nettle (Laportea canadensis) can be eaten after being cooked for a short time in boiling water. This process eliminates the stinging property of the nettle hairs. Older nettle leaves, and particularly stems, are very fibrous and are unpalatable even with cooking. Nettles should be picked carefully using gloves and never consumed raw.
Some plants normally considered edible can become toxic due to development of high levels of nitrates when under moisture stress or following exposure to frost. Examples are red root pigweed (Amaranthus retroflexis) and lamb's quarters (Chenopodium spp.).
The following wild plants are reported to be edible. This is not a complete list and is for information only. The author and The Prairie Garden do not make any warranties as to the safety of consuming any wild foods and accept no liability or responsibility for any consequences resulting from the use of or reliance upon the information contained herein, nor for any health problems, consequences or symptoms which may arise from contact with or the ingestion of any plant herein described. Most of these species are widely distributed on the Prairies and nearby forested regions.
Wild Plants Reported to be Edible
Arrowhead (Sagittaria spp.) Root tubers cooked.
Blueberries (Vaccinium angustifalium & V. myrtilloides) Ripe fruit, raw or cooked.
Buffaloberry (Shepherdia spp.) Berries are edible but have a soapy taste. Use sparingly.
Burdock (Arctium lappa) Inner part of root peeled to remove outer stem fibers and then cooked.
Cattail (Typha spp.) The base of young shoots, roots, immature seed bearing structure and pollen. This is one of the most important wild food plants. However, don't confuse it with wild iris (Iris versicolor) which is poisonous.
Currant & Gooseberry (Ribes spp.) Ripe fruit raw or cooked as jams and jellies.
Dandelion (Taraxacum officinale) Leaves and roots edible raw or cooked.
Highbush Cranberry (Viburnum trilobum) Fruit edible cooked and processed into jelly.
Jerusalem Artichoke (Helianthus tuberosus) Tuberous roots are edible raw or cooked.
Lamb's Quarters (Chenopodium spp.) Young growth as a cooked green.
Nannyberry (Viburnum lentago) Ripe fruit raw, large seed difficult to remove if cooked.
Nettle (Urtica dioica & Laportea canadensis) Young growth as a cooked green. Caution: NEVER consume raw.
Ostrich Fern (Matteucia struthiopteris) Newly emerged shoots called fiddleheads are edible when cooked.
Plantain (Plantago spp.) Young leaves as a cooked green.
Pricklypear Cactus (Opuntia spp.) Young pads cooked, with spines removed prior to cooking.
Purple Cactus (Mamillaria vivipara) Fruit edible raw or cooked.
Purslane (Portulaca oleracea) Leaves and stems raw or cooked.
Raspberries (Rubus spp.) Ripe fruit.
Redroot Pigweed (Amaranthus retroflexus) Young leaves and stems are edible as a cooked green.
Riverbank Grape (Vitis riparia) Ripe fruit raw or cooked.
Sandcherry (Prunus pumila) Ripe fruit raw or cooked. The large pits are difficult to remove.
Saskatoon/Serviceberry (Amelanchier spp.) Ripe fruit raw or cooked in pies and jams.
Strawberries (Fragaria spp.) Ripe fruit.
Thistle (Cirsium spp.) Young stems peeled to remove stem fibers and leaves with spines cut off.
Water Lily (Nuphar spp.) Tubers cooked, but very bitter taste.
Wild Onion & Garlic (Allium spp.) Bulbs used like green onions.
Wild Rose (Rosa spp.) Ripe rosehips raw or processed into a jam or jelly.
Some Poisonous Plants and Flowers
Anemone (Anemone spp.) All parts of plant are poisonous.
Baneberry (Actaea spp.) Red or white fruit is very poisonous.
Buckthorn (Rhamnus spp.) All parts of plants poisonous particularly the berries.
Bracken Fern (Pteridium aquilinum) Fiddleheads were formerly reported to be edible. Recent evidence indicates that Bracken Fern fiddleheads are potentially carcinogenic.
Buttercup (Ranunculus spp.) All parts of plant are poisonous.
Death Cammas, Smooth Cammas (Zygadenus spp.) All parts of plant, including flowers, are poisonous.
Dogbane (Apocynum spp.) All parts of plant are poisonous.
Iris (Iris spp.) All parts of plant are poisonous.
Lobelia (Lobelia spp.) All parts of plant are poisonous.
Marsh Marigold (Caltha palustris) Mature leaves and flowers are poisonous. Young leaves and unopened flower buds are reported to be edible cooked but use caution. It is advisable to avoid using this plant.
Milkweed (Asclepias spp.) All parts of plants poisonous. Some species more poisonous than others. Young seed pods of common milkweed are reported to be edible when cooked but use caution. Best to avoid.
Moonseed (Menispermum canadense) All parts of plants poisonous particularly the berries.
Mountain Laurel (Kalmia latifolia) All plant parts are poisonous.
Nightshade (Solanum spp.) All parts of plants poisonous especially the berries.
Poison Ivy (Toxicodendron radicans) Contact with plant can cause severe dermatitis, i.e., blistery rash.
Snowberry (Symphoricarpos spp.) All parts of plants poisonous particularly the berries.
Spurge (Euphorbia spp.) All parts of plants poisonous.
Vetch, Locoweed & Milk Vetch (Lathyrus spp., Vicia spp. Astragalus spp. & Oxytropis spp.) All parts of plants poisonous.
Virginia Creeper (Parthenocissus quinquefolia) All parts of plants poisonous, particularly the berries.
Water Calla (Calla palustris) All parts of plant are poisonous.
Water Hemlock (Cicuta maculata & Cicuta spp.) All parts of plants poisonous.
Most poisonous plant in North America. Avoid all look-alike plants in the Umbelliferae / Carrot family because of risk of misidentification.
Note: This is not a complete list of poisonous wild plants.
An Internet site for plant identification and distribution within North America is Flora of North America at: www.efloras.org. The most complete listing of edible plants throughout the world is Plants for a Future, a United Kingdom Web site, at: www.pfaf.org. All the information on this site is backed by literature references and an American database that includes virtually all plants likely to be found in the United States and Canada. Another reliable source of information is the U.S. Food and Drug Administration poisonous plants database, which can be found at: www.cfsan.fda.gov/~djw/plantox.html. This database contains references to the scientific literature describing studies of the toxic properties and effects of plants and plant parts.
All of these Internet sources indicate that the information is intended for research only and is not intended to replace advice obtained from medical authorities at a poison control centre.
Happy gathering, but remember, be sure to stay safe!
Dr. Gary Platford is co-Chair of The Prairie Garden Committee. He has been on The Prairie Garden Committee since 1972 and has been co-Chair or Chair since 1989/90. Gary retired from Manitoba Agriculture & Food in 2000 where he was provincial plant pathologist for 29 years. He is currently a consultant in plant pathology with P&D Agro Consulting Inc.