UNIVERSITY PARK, Pa. -- Many gardeners search for plants that are beautiful, but a gardening expert in Penn State's College of Agricultural Sciences says some plants can cause injuries or harmful effects that aren't pretty.

Most toxic plant reactions cause skin problems of some kind. Nuss says awareness and common-sense precautions can prevent most problems.

"If you develop a rash or some other symptom from contact with plants, collect a sample of all plants to which you were exposed," says Robert Nuss, professor of ornamental horticulture. "Samples will help your doctor identify the cause of the problem."

Nuss recommends that gardeners learn to identify problem plants. If exposed, gardeners should wash thoroughly as soon as possible. "Don't use soap containing oils," Nuss says. "Oils can spread toxins and promote skin absorption. Detergents or hand cleaners are the most effective."

Nuss lists some of the common plants that can have toxic or harmful effects on humans.

--"Poison" plants. Poison oak, poison ivy and poison sumac all contain the toxin urishiol in the sap of leaves, stems, fruit, flowers and roots, which can cause itchy rashes and other symptoms. The fruit of the ginkgo tree and the sap of the smoketree also can cause skin rashes.

--Allergenic plants. Most allergic reactions are caused by pollen, bringing on hay fever or asthma. Mold spores can cause allergic reactions in sensitive individuals, as can some lichens that grow on rocks or trees.

Nuss says orchids, tulip bulbs, chrysanthemums and dahlias can be allergenic to some individuals.

--Skin irritant plants. The chemicals plants have in leaves, bark, roots, bulbs or flowers can cause direct skin irritations. "In many cases the sap within the plant is the cause of the problem," Nuss explains. "Often, the irritating substance is released only when the plant tissue has been damaged or mishandled."

Nuss says some common houseplants can cause skin irritation, including poinsettias, penciltrees, daffodils, hyacinths and ornamental buttercups.

--Stinging plants. Most nettles can cause a toxic reaction when touched, but the reaction does not have lasting effects and requires no medical treatment.

--Thorny plants. The most common plant-related injuries are caused by thorns. "Most people don't seek medical help after getting stuck by a thorn," Nuss says. "But implanted thorns, needles or spines can cause infections or other medical problems."

Nuss says thorns embedded near joints can cause chronic arthritis. Thorns embedded near bones can mimic a bone tumor. Thorny plants that can cause painful injuries include roses, black locust and honeylocust trees and blackberry bushes.

"Clothing, tools and even smoke from burning plants can carry toxins," Nuss says. "Be sure to wash all clothing and tools after working with problem plants. The residues can be hazardous for a long time."

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EDITORS: For more information, contact Robert Nuss at 814-863-2196.

Contacts: John Wall jtw3@psu.edu 814-863-2719 814-865-1068 fax