If you own horses, steer clear of Savannah holly (Ilex x attenuate). Thriving in U.S. Department of Agriculture plant hardiness zones 6 through 9, the berries are toxic to horses. The toxic ingredient in the plant is ilicin, which is detrimental to the digestive system, nervous system and cardiovascular system.
Savannah holly is a narrow tree that can either be pyramidal or columnar in shape. The tree, which is native to North America, produces a spiny, dull, dark green, oval-shaped leaf that is 2 to 4 inches with wavy margins. The tree’s round, red berries, which are less than 0.5 inch, develop in the fall and usually persist throughout the fall and winter. Most trees have a central trunk with skinny, lateral branches; however some have several trunks growing straight through to the crown.
Most horses will not eat trees if other foods, such as fresh hay or forage, are available; however, even a well-fed horses has been known to try something new. Most toxic plants have a bitter taste that will usually discourage horses from dining, but it is possible for equines to develop a taste for the berries.
Symptoms & Treatment
If you believe your horse has ingested Savannah holly berries, look for symptoms, such as digestive upset, colic, tremors or seizures, difficulty swallowing, irregular heartbeat, or convulsions. If your horse is experiencing these symptoms or even if you’re worried your horse has ingested these berries, contact your veterinarian immediately. If your horse is experiencing severe symptoms, ask your veterinarian what you should do to stabilize or treat the horse until the vet arrives. Different veterinarians may want owners to take different courses of action depending on the horse's symptoms.
Planting and Pasturing
A Savannah holly tree grows at a moderate rate and can reach 30 to 45 feet high and 6 to 10 feet wide. If you would still like to plant Savannah holly, it’s a good idea to find an area away from any paddocks or pastures. Even though you should plant trees on the opposite side of the fence from your equine, you also want to consider the possibility of a horse escaping its pasture. In this instance, don't plant a Savannah holly near an exit or potential escape route.