The beauty of many common flowers can hide a deadly secret. Some plants are extremely poisonous, even deadly, to both animals and humans. Many are only poisonous in their seeds or sap. Others are toxic in every part of the plant, from the leaves to the flowers and everything in-between. While some of these plants are rarely grown, surprisingly, some of them are commonly cultivated for use as decorative landscape plants.
Oleander (Nerium oleander)
Oleander is the deadliest plant in the world, according to Web Ecoist. This showy, flowering shrub will quickly kill an adult who consumes any part of the plant. In fact, fatal poisonings have been recorded by people and animals who simply licked the twigs, berries, flowers and leaves, or handled the plant and then put their fingers in their mouths. Sadly, this is especially true in the case of children. Unfortunately, oleander is still popularly cultivated as an ornamental shrub by many home gardeners, in part due to its ease of care and attractive blooms. In some states, it is only used in areas where people do not frequent, such as highway medians.
Castor Bean Plant (Ricinus communis)
The bean (seed) of the castor plant contains the deadliest plant poison on earth, according to Web Ecoist. While the other parts of the flower are not deadly, one tiny seed can kill a child, and a few can kill an adult. Castor oil, which has health properties, is made from the beans after the toxins (in particular, ricin) have been removed. Regardless of their poisonous seeds, castor plants are another popular landscape plant. They are very showy, with leaves as large as 3 feet across, and can even be found growing in the wild in 27 states. Removal of the flowers from the plant before they can go to seed will minimize the chances of poisoning occurring.
Bushman's Poison or Wintersweet (Acokanthera spp.)
This plant is so named due to the fact that the Khoisan people of South Africa use the plant to poison their arrows. The sticky, milky sap of the flowering shrub is fatal to humans and animals. Interestingly enough, the leaves have medicinal properties, and the berries, which resemble plums in size and appearance, are tasty and edible.
Water Hemlock (Cicuta douglasii)
The U.S. Department of Agriculture (USDA) calls the water hemlock, which is widespread in western North America, "violently toxic." Just a small amount of the deadly sap, which smells like carrots, will cause violent convulsions and death even if only a tiny bit of the substance is consumed. This plant is also frequently called poison parsnip for its resemblance to the common herb. The flowers of the water hemlock, along with the stems, are harmless.