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Purpletop Tridens,

Tridens flavus

Other common name(s):

Redtop Tridens, Tall Redtop Tridens, Purpletop, Redtop, Tall Redtop

Family:

Poaceae (Grass Family)

Plant Ecoregion Distribution Map

Cross Timbers, East Central Texas Plains, Edwards Plateau, Gulf Coast Prairies and Marshes, High Plains, Southwestern Tablelands, Texas Blackland Prairies, Western Gulf Coastal Plain
Carbonate Cross Timbers, Eastern Cross Timbers, Grand Prairie, Limestone Cut Plain, Western Cross Timbers
Bastrop Lost Pines, Floodplains and Low Terraces2, Northern Post Oak Savanna, Northern Prairie Outliers, San Antonio Prairie, Southern Post Oak Savanna
Balcones Canyonlands, Edwards Plateau Woodland, Llano Uplift
Coastal Sand Plain, Floodplains and Low Terraces4, Laguna Madre Barrier Island and Coastal Marshes, Mid-Coast Barrier Islands and Coastal Marshes, Northern Humid Gulf Coastal Prairies, Southern Subhumid Gulf Coastal Prairies, Texas-Louisiana Coastal Marshes
Llano Estacado, Shinnery Sands
Canadian/Cimarron Breaks
Floodplains and Low Terraces1, Northern Blackland Prairie, Southern Blackland Prairie
Flatwoods, Floodplains and Low Terraces3, Pleistocene Fluvial Terraces, Red River Bottomlands, Southern Tertiary Uplands, Tertiary Uplands

Plant Characteristics

Growth Form

Grass & Sedge

Height

2.5
to
7
ft.

Spread

1
to
2
ft.

Leaf Retention

Deciduous

Lifespan

Perennial

Habitat and Care Requirements

Soil Type(s)

Sand, Loam, Dry, Saline

Light Requirement

Part Shade

Water Requirement

Low

Native Habitat

Grassland, Woodland

Bloom and Attraction

Bloom Color

Purple

Bloom Season

Summer, Fall

Seasonal Interest

Seeds, Larval Host, Nesting Material

Wildlife Benefit

Butterflies, Birds, Small Mammals

Maintenance

Can be used as a native ornamental grass. Attractive with its reddish-purple inflorescence when planted in mass. It is salt tolerant. Protect from browsers as it is readily eaten during early growth. Native habitat: roadsides, open woodlands. Propagation: seed.

Comments

A tall warn season grass, with drooping branches, bearing widely spaced reddish-purple spikelets. The purple seed heads are covered with an oily substance inspiring another common name, Grease Grass. Birds and small mammals eat seeds. Larval host: Cross-line Skipper, Broad-winged Skipper, Little Glassywing Skipper, Large Wood Nymph.

References

1) https://www.wildflower.org/gallery/species.php?id_plant=TRFL2, 2) https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=42227#null, 3) http://bonap.net/TDC/Image/Map?taxonType=Species&taxonId=19112&locationType=County&mapType=Normal, 4) https://portal.torcherbaria.org/portal/taxa/index.php?taxon=Tridens+flavus&formsubmit=Search+Terms, 5) Hatch, Umphres, Ardoin, 2015, Field Guide to Common Texas Grasses, pg 282, 6) https://www.prairiemoon.com/tridens-flavus-purpletop, 7) https://hamiltonnativeoutpost.com/product/purple-top/, 8) https://seedsource.com/purpletop/, 8) chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_trfl2.pdf
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About the Region

New Braunfels, the location of our Fall 2024 Symposium, straddles both the Edwards Plateau Ecoregion and the Blackland Prairie ecoregion. Interstate 35 divides the city of New Braunfels; its path through the city closely parallels the boundary of these two ecoregions, with the Edwards Plateau on the west side and the Blackland Prairies region to the east. The Edwards Plateau area is also called the Hill Country; however, this general term covers a much larger area extending farther north. Spring-fed creeks are found throughout the region; deep limestone canyons, rivers, and lakes (reservoirs) are common. Ashe juniper is perhaps the most common woody species found throughout the region. Additional woody species include various species of oak, with live oak (Quercus fusiformis) being the most common. Sycamores (Platanus occidentalis) and bald cypress (Taxodium distichum) border waterways. This area is well known for its spring wildflower displays, though they may be viewed in spring, late summer, and fall, as well. According to Texas Parks and Wildlife, average annual rainfall in the Edwards Plateau ranges from 15 to 34 inches.

The Blackland Prairie extends from the Red River south to San Antonio, bordered on the west by the Edwards Plateau and the Cross Timbers, and on the east by the Post Oak Savannah. Annual rainfall averages 30 to 40 inches, with higher averages to the east. This region is dominated by prairie species. The most common grass species include little bluestem (Schizachyrium scoparium) and Indian grass (Sorghastrum nutans) in the uplands and switchgrass (Panicum virgatum) in the riparian areas and drainages. Common herbaceous flowering plants include salvias, penstemons, and silphiums. This area has suffered greatly from overgrazing and agricultural use. Few intact areas remain, though many of the plants can be found along county roadsides throughout the region.

Our four host chapters (New Braunfels, Lindheimer, Guadalupe, and the Hill Country chapters) are located in one or both of the ecoregions above. However, the eastern portion of Guadalupe County also falls within the Post Oak Savanna ecoregion. Annual rainfall averages 35 to 45 inches, with higher averages to the east. A wide variety of hardwood trees are found, including several species of oaks, elms, and in the Bastrop area, loblolly pine (Pinus taeda). Grasses and forbs dominate in the open savannas, with most common grass being little bluestem. Ranching, agriculture, and fire suppression have allowed woody species to encroach on the once-open savannas.

Source: Wildflowers of Texas by Michael Eason