Is the Butterfly Plant Poisonous to Animals or Humans?

Think of it as a butterfly restaurant: the butterfly bush (Buddleja davidii) ranks near the top of the list of plants that call monarch and painted lady butterflies to dine. While you won't want to feed the long, tapered flower clusters to your kids or your dog, the plant is not known to be toxic to people or animals. But butterfly weed (Asclepias spp.) is toxic to both.

Without its flowers, butterfly bush is rather plain. The shrubby plant grows rapidly in U.S. Department of Agriculture plant hardiness zones 5 through 10, producing long, arching branches with gray-green leaves that stay on the bush all winter in USDA zones 7 through 10. The flowers are the main attraction -- especially for butterflies. The individual blossoms are tiny, but they appear in dense, cone-shaped clusters that arch the boughs even lower to the ground with their weight. You can find cultivars with the traditional deep purple flowers, but also pink, red and white. The flowers and foliage are not known to be toxic.

Because butterflies are not likely to be the only small things zipping about your garden, the question of butterfly bush's toxicity raises its ugly head. But you shouldn't be concerned. University of California lists the butterfly bush as nontoxic to humans, and ASPCA has no data suggesting dogs, cats or other pets will get more than a stomachache if they eat the plant. Because each person or pet could potentially have an adverse reaction to any plant, it is always best to prevent children and pets from eating flowers or leaves.

Don't confuse butterfly bush with shrubs commonly called butterfly weed or milkweed (Asclepias spp.), native plants that attract butterflies and other insects with showy flower clusters. These perennials grow in USDA zones 3 through 9, and common milkweed (Asclepias syrica) and its relatives are the only plants on which monarch butterflies lay eggs. Like butterfly bush, some types of butterfly weed are considered invasive in some regions because they grow so easily and quickly. Unlike the butterfly bush, butterfly weed is toxic and can cause poisoning or kill children or pets.

All parts of the butterfly weed are toxic -- flowers, leaves, stems and roots. Both humans and animals will suffer if they eat it. If you or your kids eat some, you may experience diarrhea or vomiting; if you touch the sap, the skin can burn or itch. If your pets chow down on butterfly weed, they could be in more trouble because small doses -- as low as 0.1 to 0.5 percent of an animal's body weight -- might kill the animal. Generally this is more of a problem for grazing animals, not household pets. If you suspect your child or pet has eaten some of this plant, get emergency medical attention.