By Bill Cook, Ohio Chapter Volunteer
w/ August Froehlich & Rick Gardner

Poison sumac, Toxicodendron vernix, belongs to a class of plants that also includes poison ivy and poison oak. A representative of this group grows almost everywhere in the United States except Alaska, Hawaii, and some parts of Nevada.  Poison sumac can be found in most of our Ohio preserves, and like most plants it has many common names including poison weed, poison wood, poison tree, swamp or varnish sumac, thunderwood, and poison dogwood, ash or elder. Brown’s Lake Bog, is one Ohio Chapter preserve where volunteers work diligently to control this wetland invader.

Poison sumac is a water loving shrub or small tree which grows 6 to 20 feet in height. It has pinnately compound leaves with 5 to 13 smooth leaflets per leaf. The bark is light to dark grey in color and either smooth or slightly streaked.  The sap is clear, but quickly turns black when exposed to the air.  Poison sumac has tiny, sweet smelling flowers in the spring. During the autumn season it is covered with lovely, bright red and yellow leaves, and has cream colored berries.

The chemical responsible for this plant’s poisonous distinction is urushiol, a sticky, clear oil that flows through the poison sumac plant and coats its leaves.  This oil, which contains catechols and other phenolic resins, remains stable even in dead or dried plants, and therefore is equally hazardous throughout all seasons.  Although urushiol will break down with composting, this is not recommended because the plants must be chopped into small pieces first, which increases the amount of exposure to the plant and risk of a rash. The resin can be carried by smoke if the plant is burned and may cause lung irritation. Ingesting any part of the plant can cause a reaction in the oral cavity and gastrointestinal tract.  A protection program of recognition, avoidance, and protective clothing form the basis of a defense against poison sumac, which can cause bothersome allergic skin reactions that can take two to three weeks to heal.

One of the greatest threats to the integrity of this glacial relict bog community is succession. This phenomenon may be unnaturally accelerated due to changes in hydrology, increased runoff, and changes in water chemistry caused by surrounding agricultural areas.  Without intervention, woody plants such as poison sumac would encroach upon the sphagnum mat and would eventually shade out the bog species that make this area unique.

During the winter field season, a main focus of volunteer efforts at Brown’s Lake Bog includes control of woody species like poison sumac.  Volunteer crews work to open the bog mat by thinning currently shrubbed-over areas around the water, much of which has been heavily encroached upon over the past two decades.  There are many means by which poison sumac may be controlled or removed from a natural area.  Young plants may be pulled from the ground when soil is wet.  Attempts to remove roots from dry soil are not as beneficial, as remaining root fragments in the soil will sprout vigorously and replace the original plants.  Repeated cutting of the plant back to the ground surface will eventually starve the root system and the plant will die.  However, manual extraction and repeated cutting increases the chances of exposure to urushiol.