Know What Is In Your Pastures

By Helene McKernan, Clinton Co Extension

 Many of these plants provide habitat for wildlife and are vital in honey bee production by pollinating crops insuring, especially fruit trees, continual reproduction. I usually purchase some of the plants at the sale to plant around my barn to make it more appeasing in appearance and also to reduce weed growth.  The plants I choose to utilize around my barn must be hardy (barn cats love to destroy flower beds), need little maintenance (I don’t have that green-thumb that others have), but most importantly must be non-toxic to horses.  Though I don’t let my horses graze directly around my barn I am not naïve to realize that birds, wind and other methods can spread seeds leading to undesirable plant establishments.  Plants can germinate in an unacceptable area, but my main concern is in the pastures my horses utilize for forage.  

So what plants are undesirable and potentially toxic to horses?  The list is long and can include both “domestic” plants, wild plants, flowering plants and weeds.  Often a horse must eat a large quantity of toxic plants to do damage to their system, but sometimes just a few bites can be detrimental.  In some cases ingesting is not the problem, but the physical exposure to the leaves and wood parts by touch.  If a horse has acceptable forage grasses mixed in with weeds and flowers within the pasture, the horse will usually eat the grasses or weeds that do not harm them.  This is because toxic weeds and flowers are usually bitter when ingested.   But, if the pasture becomes overgrown, the haven for weed growth, the horse in desperation will consume undesirable plants.  Do weeds or grasses have a better survival life?  The answer is weeds.  They are more hardy and adaptable in drought, floods and overgrazing situations.

Often I am asked, “Should I eliminate all weeds from my pasture?”  My answer would be no, for a couple of reasons.  First, it will take extensive and expensive care to maintain a weed free pasture and it is a difficult battle, since weeds will re-seed themselves yearly.  The other reason is weeds do provide a vegetative cover and prevent soil erosion, plus some provide nutritional value in the horse’s diet.  Most horses enjoy and seek out the tasteful bites of the dandelion plant, which is nutritional and non-toxic to horses.  With the 2011 PA Manure Management Plan all pastures need to exhibit a 70% vegetative cover and weeds can be part of that cover.  Many weeds are a nuisance for the horse owner, such as plants that produce burrs or thorns.  Often these weeds are not toxic to horses, but we desire to eliminate them because they often over-run fence lines and become tangled in the horse’s mane and tail.

Desirable grass forage can also cause issues for horses.  Clover is host to a toxin growth that can cause “slobbers” in horses.  Tall fescue can be detrimental in the breeding operations causing still-born, abortion and dead in foals.  Other grasses are a cause for photosensitive issues and metabolic issues.  The horse owner needs to know what is growing in the pasture to be prepared for issues vegetative growth can induce when digested by the horse.

Some of the toxic weeds and plants that should be eliminated or controlled within the pasture include: Buttercups, Horsenettle, Pokeweed, Nightshade varieties, Poison Hemlock, Water Hemlock, Jimson, Milkweed, Cherry (black, pin and choke), Red Maple, Black Walnut, budding Oak leaves and acorns, Rhododendron, Mountain Laurel, Azalea, Bracken Fern, Yew

(English or Japanese), Lilly of the Valley, day lilies, Tulips, Hyacinths, Boxwood, Trumpet Vine, Wisteria, Clematis, Bleeding Hearts, Dutchman’s Breeches, Foxglove, English Ivy, Hydrangea, Holly, Morning Glory, Iris, Lupine and Daffodil.  Are these all of the toxic plants?  Unfortunately, the list can go on and on, but these are the most common domestic and wild plants, trees and weeds that we find existing in the Northeast region. 

You may have noticed that many of the plants mentioned as toxic are found in wetlands and forest areas.  Horse pastures should not be constructed in those areas.  Horses in the wild exist on open grassland and only use forest areas for protection during inclement weather and only visit wetland areas when finding a drinking source.  Horses pastured in areas surrounding creeks and wetlands tend to have issues with mud induced ailments, plus the hoofs of the horses are very destructive to soils that are wet and soft.  Many grasses cannot endure disturbance in wetland areas and that is why those areas tend to be populated by non-grass growth.

If you have difficulty in identifying the undesirables there are many resources such as the book, The Weeds of the Northeast by Richard Hart Uva, Joseph Crowell Neal, and Joseph M. DiTomaso.  Identifying Pasture Grasses by Dan Undersander, Michael Casler, Dennis Cosgrove and Identifying Pasture Legumes by Dennis Cosgrove and Dan Undersander are both excellent resources for identifying desirable pasture forage.  There is an extensive resource of flowering plants for both gardens and wild flowers that could be found on line or in your local bookstore.  Contact your local extension office for assistance in locating weeds, plant and grass resources.  Penn State has a variety of fact sheets and resources available at publications http://pubs.cas.psu.edu/Publications.asp.