There are 18 species and several varieties of knotweeds in Texas. These plants are herbs or herbaceous-textured vines without tendrils. They have alternate, usually lance-shaped leaves. The branching stems are erect or ascending; the enlarged nodes often take root where they contact bare ground. The very small, white to pinkish-red flowers usually form loose spikes.
Knotweeds are found in all vegetational areas of Texas. They are usually found in wet areas and around ponds and streams, and are therefore more abundant in the eastern part of the state.
The toxic agent is not known. Consumption of these plants has been associated with primary photosensitization, and until research is completed to show otherwise, all species should be considered as potentially toxic. Vegetation from species associated with field cases contains photodynamic compounds not yet identified. Feeding trials with knotweed seed in grain screenings did not cause problems or disease.
The clinical signs are those of sunburn and include: Photophobia (animals try to stay in the shade); Reddening of light colored skin; Crusting and cracking of nonpigmented skin;• Sloughing of affected skin.
Young calves on cows with severe udder lesions may not be allowed to nurse and can suffer significant weight loss.
Flower Color: Pink, White
Seed Type: Non-Encapsulated
Stem Texture: Hairless/Smooth
Growth Habit: Forbs/Broadleaf
Distribution : 01 - Pineywoods, 02 - Gulf Prairies and Marshes, 03 - Post Oak Savannah, 04 - Blackland Prairies, 05 - Cross Timbers and Prairies, 06 - South Texas Plains, 07 - Edwards Plateau, 08 - Rolling Plains, 09 - High Plains, 10 - Trans-Pecos
Distribution refers to the ecological region in Texas that a plant has been found. You can also view a clickable map.
Book: Toxic Plants of Texas (B-6105)
Collection: Toxics, Wild Flowers
Livestock Affected: Cattle, Goats, Horses, Sheep