Will Rhododendrons Cause an Allergic Reaction?

Allergies

• Rhododendrons are listed by Asthma Foundation Washington as being low allergen plants, rarely causing asthma, hay fever or dermatitis. Pollen Library states that rhododendrons are infrequently reported as a source of pollen allergies. Asthma Foundation Washington notes that in general, plant allergies are worst after light rains in spring and early summer, as this breaks up large pollen grains and causes small particles to float through the air. This may also occur when watering plants with a light spray of water.

Human Toxicity

• If ingested, rhododendrons can cause poisoning symptoms such as watering nose and eyes, abdominal pain, loss of energy, nausea and vomiting. More serious symptoms include difficulty breathing, a worsening paralysis of the arms and legs and, eventually, coma. According to North Carolina State University, the plant is highly toxic and may even be fatal. Call 911 or the free, 24-hour American Association of Poison Control Centers Poison Help Line at 800-222-1222 if you suspect you or someone you know has been poisoned by a rhododendron.

Pet Toxicity

• Rhododendrons are toxic to horses, cats and dogs. Horses rarely graze on the plant, usually doing so only when desperate. Symptoms of poisoning in pets generally occur within a few hours of ingesting the plant and include diarrhea, weakness, vomiting, depression, heart failure and death, according to the ASPCA. If you suspect your pet has ingested rhododendron, call your local veterinarian or the ASPCA Animal Poison Control Center at 888-426-4435. The ASPCA may charge a consultation fee.

Culture

• Exact hardiness varies depending on species, though rhododendrons in general will grow in U.S. Department of Agriculture plant hardiness zones 4 to 9. Rhododendrons require acidic soil enhanced generously with organic matter and mulch with leaves or pine needles. They generally prefer filtered, shifting shade, though some will grow in full sunlight or full shade. Rhododendrons must be watered regularly throughout the growing season in order to thrive. Prune immediately after flowering if desired.