Giant Hogweed Identification Guide Heracleum mantegazzianum

Giant Hogweed Has Been Reported in the Southeast! A population of giant hogweed was recently confirmed in Virginia. A landscaped planting had escaped and spread. Whenever a new population of this dangerous plant is found, it is important to report it. Giant hogweed can be reported to EDDMapS.org or to the County Extension Agent.

Giant hogweed was found on three occasions in the North Carolina mountain region a few years ago. One report was from a residential garden. The other two reports were from the same county. A single plant was found in a drainage ditch along a roadway, and the other was a single plant alongside a small stream. These escaped populations were found in the type of habitat where giant hogweed does well. All three populations were removed. Giant hogweed can be successfully controlled if it is found, reported and removed quickly, as it was in North Carolina and Virginia.

Giant hogweed is an herbaceous plant that can grow up to 15-20 feet in height. Giant hogweed can outcompete native species for habitat, especially in riparian zones. It is found along roadsides, empty untended lots, wet ditches and along streams and rivers. It prefers rich, moist soil, in semi-shade conditions.

This plant is on the federal noxious weed list because of its toxic sap. This sap makes skin very sensitive to UV radiation, causing blistering and severe burns. Caution should be taken when handling this weed.

Giant hogweed, Heracleum mantegazzianum’s specs:

Stems: Hollow and usually blotched with purple. Both stems and leaf stalks have bristly hairs. The stem can be 2-4 inches in diameter.

Leaves: Leaves are sharply and deeply lobed and up to 5 feet across. Seedling leaves are much less deeply lobed.

Flowers: Blooms from in summer. Small white flowers are held in flat topped clusters that can be 2.5 feet wide.

In the photo above, leg burns caused Fruits: Tan ovals less than 1 inch long with small, dark seeds by exposure to sun after contact with sap from giant hogweed. inside. Plants can produce 20,00 seeds in a season. PLANTS STEMS LEAVES FLOWERS Giant hogweed, Heracleum mantegazzianum: Extremely Toxic Most of these plants are in the carrot family and are closely related. They look alike in many ways. This guide will focus on how each of the other species listed here is different from giant hogweed. Stems are green with purple splotches and coarse white hairs -thick circle of hairs at base of leaf stalk, 2-4 inches in diameter. Compound, lobed, deeply incised, up to 5 feet wide. White umbrella-shaped flower clusters up to 2.5 feet wide with 50 or more rays per cluster.

Water hemlock, Cicuta maculata: Water hemlock is extremely poisonous. Biennial to short lived perennial plant from 3-9 feet tall. Rounded stems are green to reddish purple. Double or triple pinnately compound leaves can be up to 1 foot long by 2 feet wide. Small white flowers are in many flat topped clusters only about 6 inches across.

Poison hemlock, Conium maculatum: Poison hemlock is native to Europe and is extremely poisonous.It is a biennial herbaceous plant from 3-8 feet tall. Stems are very smooth and waxy. The purple spotting is variable. Some plants have almost no purple coloration while others are extremely purple-colored. Leaves are finely dissected, giving them a ‘fern-like’ appearance and they clasp the stem at the swollen nodes. Flowers are small, white, and held in flat clusters about 3 inches across. Fruits are ridged and flattened, and each fruit holds two seeds.

Cow parsnip, Heracleum lanatum: Extremely Toxic Biennial to short lived perennial herbaceous plant from 4-8 feet tall. Rounded green stem has ridges. It has fine white hairs and is 1-2 inches in diameter. Leaves are compound, less deeply incised than hogweed, between 2 -2.5 feet across. Small white flowers are held in flat topped clusters no more than 12 inches across and only 15-30 rays per cluster.

Angelica species: About 5 species of Angelica are found in the southeastern United States. Many plants in this family are toxic, so exercise caution when handling it. Angelicas are perennial herbaceous plants which can grow 2-6 feet tall. Smooth stems with no hairs. Small greenish-yellow to greenish-white flowers are held in ROUNDED ball-like clusters. Compound leaves have coarsely-toothed leaflets.

Elderberry, Sambucus species: Deciduous shrub growing up to 12 feet tall. Multiple long stems grow from the base arching over at the top. Stems are NOT hollow. Pinnately-compound leaves are opposite and up to 12 inches long. Small white flowers are held in flat topped clusters 10 inches or more across. They bloom from May to July. Berry like fruits are dark purple when mature. Giant Hogweed Identification Guide Heracleum mantegazzianum

Giant hogweed leaves are sharply and deeply lobed and up to 5 feet across. It is important to note that seedling’s leaves are much less deeply lobed.

Immature fruits Mature fruits and seeds

References: All images are from Images.bugwood.org www.illinoiswildflowers.info Front cover - Robert Vidéki, Doronicum Kft.; USDA APHIS PPQ - Oxford, North Carolina , USDA APHIS PPQ. Chart - Leslie J. Mehrhoff, University of Connecticut; Leslie J. Mehrhoff, University of Connecticut; Leslie J. Mehrhoff, www.fs.fed.us/wildflowers University of Connecticut; Leslie J. Mehrhoff, University of Connecticut; Leslie J. Mehrhoff, University of Connecticut; plants.ifas.ufl.edu Robert Vidéki, Doronicum Kft.; Karan A. Rawlins, University of Georgia; Karan A. Rawlins, University of Georgia; Chris www.invasive.org Evans, University of Illinois; Karan A. Rawlins, University of Georgia; Pedro Tenorio-Lezama; Eric Coombs, Oregon www.wildflower.org Department of Agriculture; Robert Vidéki, Doronicum Kft.; Pedro Tenorio-Lezama; Ohio State Weed Lab , The Ohio State University; Ohio State Weed Lab , The Ohio State University; Rob Routledge, Sault College; Dave Powell, USDA www.dec.ny.gov/animals/72766.html Forest Service (retired); Mary Ellen (Mel) Harte; Mary Ellen (Mel) Harte; Mary Ellen (Mel) Harte; Mary Ellen (Mel) Harte; James H. Miller, USDA Forest Service; David Stephens; Rebekah D. Wallace, University of Georgia; John Cardina, Citation: Rawlins, K.A., S.J. Swain, C.T The Ohio State University. Bargeron and D.J. Moorhead. Back cover - Leslie J. Mehrhoff, University of Connecticut; Leslie J. Mehrhoff, University of Connecticut; Leslie J. BW-2018-112. 4 p. Mehrhoff, University of Connecticut; Cesar Calderon, USDA APHIS PPQ.

JULY 2018