Why are Honeysuckle Plants Poisonous to Dogs?

Honeysuckles (Lonicera spp.) are typically included on lists of plants poisonous to dogs. Toxins in the sap and berries of honeysuckles can cause vomiting, diarrhea, and heart and breathing problems in dogs that eat the plants. Toxicity levels vary among honeysuckle species and cultivars, but, to keep your dog safe, try to prevent it from eating any kind of honeysuckle plant.

Toxin Information

All honeysuckle plant parts contain the toxins saponic and cyanogenic glycosides in the sap. In large doses, cyanogenic glycosides cause symptoms like cyanide poisoning causes, including vomiting, diarrhea, slow or fast heart rate, pale mucus membranes and respiratory failure. Saponic glycosides also cause digestive issues, as well as weakness, fever and difficulty breathing.

Honeysuckle berries contain carotenoids, which are also considered toxic to dogs. In low doses, carotenoids, including beta-carotene, are not dangerous. If your dog eats too much of them, however, they can lead to a loss of appetite, weakness, constipation, bone damage and death.

If your dog eats any part of a honeysuckle plant, call your veterinarian immediately. Tell him that your dog ate honeysuckle, which parts of the plant were ingested and about how much the dog ate. If you can't get in touch with your veterinarian and the dog displays severe symptoms, such as difficulty breathing or an irregular heart rate, rush the pet to an emergency veterinary clinic.

Poisonous Honeysuckles

About 180 types of honeysuckles exist. Although not all of them may be poisonous, several of the common types are toxic. Most toxic plant lists that include honeysuckle do not specify honeysuckle species or cultivars. So assume that any honeysuckle your dog eats is potentially poisonous. Commonly grown honeysuckle varieties include:

• Japanese honeysuckle (Lonicera japonica), which grows as a perennial, or is hardy, in U.S. Department of Agriculture plant hardiness zones 4 through 10. It's an aggressive vine with dark-green leaves and white flowers. Its fruits are toxic to humans as well as pets, and turn blue-black when mature. 
  
• Common honeysuckle (_Lonicera periclymenu_m ‘Harlequin’), a vine hardy in USDA zones 5 through 9. Its leaves are two shades of green with white edges. The plant's flower buds are purple-pink and open with a light-pink or cream color. 
  
• Coral honeysuckle (Lonicera sempervirens), hardy in USDA zones 4 through 9. This vine has green leaves and coral-colored flowers that attract hummingbirds. Its fruits are bright red.
  
• Tartarian or tatarian honeysuckle (Lonicera tatarica), which grows as a shrub and is hardy in USDA zones 3 through 8. Its leaves are light green or blue-green. It has reddish pink flowers that are followed by bright, red-orange berries.

Honeysuckle Removal

Some honeysuckle varieties are considered invasive in the United States. Hand-pulling seedlings works to remove or control the spread of the least aggressive varieties, but herbicide may be needed to kill more invasive varieties, such as Japanese honeysuckle, and plants that have passed the seedling stage.

Use a concentrated herbicide that is 41 percent glyphosate, mixing 4 to 5 tablespoons of it with 1 gallon of water and putting the mixture in a garden sprayer. On a windless day, use the garden sprayer to cover honeysuckle leaves thoroughly with the herbicide-water mixture. Avoid getting the solution on plants you don't want to kill. Keep people and pets away from the area while you spray, and keep them away from the sprayed plants until the solution has dried. When you mix and apply the herbicide, protect yourself by wearing waterproof gloves and shoes, a hat, goggles, a face mask and clothing that covers the rest of your skin.