Why Region Matters for Toxic Plant Risk
Texas spans 268,596 square miles with dramatically different ecological regions, each hosting distinct toxic plant communities. This guide helps ranchers identify the specific toxic plant threats most relevant to their geographic location, so the information you're getting actually applies to where you ranch.
---
Texas Ecological Regions
Region Map Overview
``` ┌─────────────────────────────────────────────────────────────┐ │ │ │ TEXAS REGIONS │ │ │ │ ┌───────────────────┐ │ │ │ HIGH PLAINS │ │ │ │ (Panhandle) │ │ │ └─────────┬─────────┘ │ │ │ │ │ ┌─────────────────┼─────────────────┐ │ │ │ │ │ │ │ │ ROLLING │ CROSS │ PINEY │ │ │ PLAINS │ TIMBERS │ WOODS │ │ │ │ │ (East Texas) │ │ │ │ ┌─────────────┼───────┐ │ │ │ │ │ BLACKLAND │ │ │ │ └────────┬────────┘ │ PRAIRIES │ │ │ │ │ └──────┬──────┘ │ │ │ ┌────────┴────────┐ │ │ │ │ │ │ ┌────┴────┐ │ │ │ │ TRANS-PECOS │ │ HILL │ │ │ │ │ (Far West) │ │ COUNTRY │ │ │ │ │ │ └────┬────┘ │ │ │ └──────────────────┘ │ │ │ │ ┌─────┴─────┐ │ │ │ │ SOUTH │ │ │ │ │ TEXAS ├────────┘ │ │ │ BRUSH │ │ │ │ │ GULF │ │ └───────────┤ COAST │ │ │ PRAIRIES │ │ └──────────────────────┘ │ │ └─────────────────────────────────────────────────────────────┘ ```
---
Region 1: High Plains (Panhandle)
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | Dallam, Sherman, Hansford, Ochiltree, Lipscomb, Hartley, Moore, Hutchinson, Roberts, Hemphill, Oldham, Potter, Carson, Gray, Wheeler, Deaf Smith, Randall, Armstrong, Donley, Collingsworth, Parmer, Castro, Swisher, Briscoe, Hall, Childress, Bailey, Lamb, Hale, Floyd, Motley, Cottle |
| Elevation | 3,000-4,500 ft |
| Annual rainfall | 15-20 inches |
| Primary land use | Cattle ranching, feedlots, irrigated crops |
| Soil type | Sandy loam to clay |
Priority Toxic Plants
#### High Threat
- Specific species: Woolly locoweed (O. sericea), Lambert's locoweed (O. lambertii)
- Peak risk: Spring (March-May) when green and palatable
- Local notes: Major concern in native rangeland; animals may develop addiction
- Risk factors: Increases with overgrazing
- Peak risk: Late winter when other forage scarce
- Local notes: Causes abortion in cattle; indicator of rangeland deterioration
- Risk factors: Nitrate accumulation during drought
- Peak risk: Summer drought conditions
- Local notes: Feedlot perimeters and irrigated field edges
- Common in disturbed areas
- Drought increases toxicity
- Very common
- Drought stress increases risk
- Common pasture crop
- Frost and drought increase danger
Seasonal Risk Calendar - High Plains
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Broom snakeweed (animals eating due to lack of forage) |
| Mar-Apr | Locoweed emergence and peak palatability |
| May-Jun | Locoweed, early nitrate concerns |
| Jul-Aug | Nitrate accumulation (pigweed, kochia, sorghum) |
| Sep-Oct | First frost dangers (sorghum, sudan) |
| Nov-Dec | Hay contamination, snakeweed |
Region 2: Rolling Plains
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | Hardeman, Foard, Wilbarger, Wichita, Clay, Montague, King, Knox, Baylor, Archer, Jack, Wise, Stonewall, Haskell, Throckmorton, Young, Palo Pinto, Parker, Kent, Fisher, Jones, Shackelford, Stephens, Eastland, Erath, Scurry, Borden, Howard, Mitchell, Nolan, Taylor, Callahan, Coleman |
| Elevation | 1,500-3,000 ft |
| Annual rainfall | 20-28 inches |
| Primary land use | Cow-calf operations, small grains |
| Terrain | Rolling grasslands with mesquite invasion |
Priority Toxic Plants
#### High Threat
- Widespread on native range
- Spring peak risk
- Affected species: Sheep highly susceptible; cattle less so
- Peak risk: Winter and early spring
- Local notes: Causes bitter milk; economic losses in sheep operations
- Spring buds and fall acorns
- Cattle preferentially graze when other forage limited
- Cumulative toxicity
- Common on overgrazed range
- Sheep more susceptible
- Common on rocky outcrops
- Can cause impaction if consumed in large quantities
- Moldy beans more dangerous
Seasonal Risk Calendar - Rolling Plains
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Bitterweed (winter grazing) |
| Mar-Apr | Oak buds, locoweed |
| May-Jun | Locoweed, early drought stress |
| Jul-Aug | Drought-stressed forages |
| Sep-Oct | Acorn accumulation, first frost |
| Nov-Dec | Bitterweed, hay quality |
Region 3: Cross Timbers and Blackland Prairies
Regional Characteristics
| Factor | Description |
|---|---|
| Geography | Transition zone between eastern forests and western prairies |
| Counties | Cooke, Grayson, Fannin, Lamar, Red River, Denton, Collin, Hunt, Hopkins, Delta, Tarrant, Dallas, Rockwall, Kaufman, Ellis, Navarro, Hill, McLennan, Falls, Limestone, Freestone |
| Annual rainfall | 30-40 inches |
| Primary land use | Mixed farming, cow-calf, stocker operations |
| Vegetation | Oak-hickory savanna, tallgrass prairie remnants |
Priority Toxic Plants
#### High Threat
- Specific species: Post oak, blackjack oak, live oak
- Peak risk: Spring (young leaves, buds); Fall (heavy acorn years)
- Local notes: Major concern due to oak dominance
- Risk factors: Prussic acid after frost or drought stress
- Peak risk: Post-frost, drought regrowth
- Local notes: Highly invasive; problematic in hay fields
- Peak risk: Spring (seedlings) after flooding
- Local notes: Cotyledon stage most toxic
- East side of region
- Causes "trembles" (milk sickness)
Seasonal Risk Calendar - Cross Timbers/Blackland
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Hay contamination issues |
| Mar-Apr | Oak budding peak danger |
| May-Jun | Cocklebur seedlings (post-flooding), Johnsongrass |
| Jul-Aug | Drought stress in Johnsongrass |
| Sep-Oct | Acorn accumulation, early frost risks |
| Nov-Dec | Post-frost Johnsongrass |
Region 4: Piney Woods (East Texas)
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | Bowie, Cass, Morris, Titus, Camp, Marion, Harrison, Upshur, Wood, Franklin, Red River (east), Gregg, Rusk, Panola, Shelby, Smith, Cherokee, Nacogdoches, San Augustine, Sabine, Anderson, Houston, Trinity, Angelina, Polk, Tyler, Jasper, Newton, Hardin, Orange, Jefferson |
| Annual rainfall | 40-56 inches |
| Terrain | Pine-hardwood forests, rolling to hilly |
| Primary land use | Mixed forestry and cattle, cow-calf |
| Climate | Humid subtropical |
Priority Toxic Plants
#### High Threat
- Peak risk: Late summer/early fall (September-October)
- Toxicity: Causes acute respiratory distress syndrome (ARDS)
- Local notes: MAJOR regional concern; cattle deaths common in fall
- Post-flood seedling emergence
- Spring primary risk
- Peak risk: Late summer when flowering
- Local notes: Historical cause of "milk sickness"
- Year-round danger
- Extremely toxic
- Berries and bark toxic
- Fall berry drop risk
- Some cattle sensitivity
- Storm damage creates risk
- Storm damage risk
- Common in forest edges
Regional Unique Concerns
- Cumulative toxicity (cancer risk in cattle)
- Thiamine deficiency in horses
- Spring flowering
- Generally avoid but can cause problems
Seasonal Risk Calendar - Piney Woods
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Yew (evergreen), hay quality |
| Mar-Apr | Buttercup in wet areas, new growth |
| May-Jun | Flooding → cocklebur seedlings |
| Jul-Aug | White snakeroot flowering |
| Sep-Oct | PERILLA MINT PEAK - major concern |
| Nov-Dec | Chinaberry berries, storm damage debris |
Region 5: Hill Country (Edwards Plateau)
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | Bandera, Blanco, Burnet, Comal, Edwards, Gillespie, Hays, Kendall, Kerr, Kimble, Kinney, Llano, Mason, McCulloch, Medina, Menard, Real, San Saba, Schleicher, Sutton, Travis, Uvalde, Val Verde |
| Elevation | 1,000-3,000 ft |
| Annual rainfall | 18-32 inches |
| Terrain | Limestone hills, rocky soils, spring-fed streams |
| Primary land use | Goat/sheep, cattle, exotics, hunting leases |
Priority Toxic Plants
#### High Threat
- Specific species: Live oak, shin oak, Spanish oak, post oak
- Peak risk: Spring buds; heavy mast years in fall
- Local notes: Shin oak particularly problematic (browsing height)
- Sheep major concern
- Winter/early spring peak
- Toxicity: Hepatogenic photosensitization
- Affected species: Sheep and goats primarily
- Local notes: "Goat fever" or "swellhead"
- Seeds highly toxic
- Cattle generally avoid
- Cedar oil abortion concerns (minimal evidence)
- More economic impact from forage competition
- Sheep/goat concern
- Photosensitization
- Cattle highly susceptible
- Spring emergence
Regional Unique Concerns
- Unripe fruit can cause GI upset
- Berries can cause mild GI effects
Seasonal Risk Calendar - Hill Country
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Bitterweed (sheep), limited forage |
| Mar-Apr | Oak budding - MAJOR concern |
| May-Jun | Lechuguilla, drought stress beginning |
| Jul-Aug | Drought stress, nitrate concerns |
| Sep-Oct | Heavy acorn years |
| Nov-Dec | Bitterweed, oak acorns persisting |
Region 6: South Texas Brush Country
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | Webb, Zapata, Jim Hogg, Brooks, Starr, Hidalgo, Cameron, Willacy, Kenedy, Kleberg, Nueces, Jim Wells, Duval, La Salle, McMullen, Live Oak, Bee, San Patricio, Refugio, Aransas, Calhoun, Victoria, Goliad, Karnes, Wilson, Atascosa, Frio, Zavala, Dimmit, Maverick |
| Climate | Semi-arid to subtropical |
| Annual rainfall | 16-30 inches |
| Terrain | Brush (mesquite, huisache, prickly pear), coastal prairie |
| Primary land use | Cattle ranching, hunting |
Priority Toxic Plants
#### High Threat
- Toxicity: Hepatogenic photosensitization
- Peak risk: Year-round, berry production
- Local notes: MAJOR regional concern
- Toxicity: Limberleg in goats, some cattle effects
- Risk factors: Heavy consumption when other forage limited
- Local notes: Important browse, problematic in excess
- Toxicity: Progressive paralysis (ascending)
- Affected species: All livestock
- Local notes: Fruit most toxic; recovery if caught early
- Causes "trembles" similar to white snakeroot
- Fall flowering peak
- Nitrate and oxalate concerns
- Excessive consumption can cause problems
- Often fed during drought (properly prepared)
- Pods can cause impaction
- Generally not major concern
Regional Unique Concerns
- Hair loss, poor condition
- Adaptation occurs over time
- Cardiac glycosides (like regular oleander)
- Extreme toxicity
Seasonal Risk Calendar - South Texas
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Limited forage → unusual plant consumption |
| Mar-Apr | New growth generally safer |
| May-Jun | Lantana berries, drought stress beginning |
| Jul-Aug | Drought stress, nitrate plants |
| Sep-Oct | Rayless goldenrod, continued drought |
| Nov-Dec | Coyotillo fruit, guajillo excess |
Region 7: Trans-Pecos (Far West Texas)
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | El Paso, Hudspeth, Culberson, Jeff Davis, Presidio, Brewster, Terrell, Pecos, Reeves, Ward, Loving, Winkler, Ector, Crane |
| Elevation | 2,500-8,000 ft |
| Annual rainfall | 8-16 inches |
| Terrain | Desert mountains, Chihuahuan desert |
| Primary land use | Extensive cattle ranching |
Priority Toxic Plants
#### High Threat
- Specific species: Woolly locoweed, other Astragalus
- Peak risk: Spring green-up
- Local notes: Major concern in this region
- Sheep/goat primary concern
- Year-round risk
- Abortion risk
- Winter consumption
- Photosensitization
- Sheep/goat concern
- Some toxicity reports
- Generally avoided
- Cumulative liver damage
Regional Unique Concerns
- Not typically grazed
- More curiosity than practical concern
- Chronic selenium toxicity possible
- Monitor in known high-selenium areas
Seasonal Risk Calendar - Trans-Pecos
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Snakeweed consumption |
| Mar-Apr | Locoweed emergence and peak |
| May-Jun | Locoweed, drought conditions |
| Jul-Aug | Monsoon can bring new growth risks |
| Sep-Oct | Lechuguilla year-round |
| Nov-Dec | Limited forage → consumption of marginal plants |
Region 8: Gulf Coast Prairies and Marshes
Regional Characteristics
| Factor | Description |
|---|---|
| Counties | Chambers, Galveston, Brazoria, Matagorda, Jackson, Wharton, Fort Bend, Harris, Liberty, Jefferson, Orange, Colorado, Lavaca, De Witt |
| Annual rainfall | 40-55 inches |
| Terrain | Coastal prairies, wetlands, rice country |
| Primary land use | Cattle ranching, rice farming, mixed |
| Climate | Humid subtropical |
Priority Toxic Plants
#### High Threat
- Peak risk: Spring seedling emergence after flooding
- Local notes: Major regional concern due to wet conditions
- Hurricane debris can spread
- Year-round danger
- Peak risk: Spring emergence
- Local notes: Check wet pasture edges, pond margins
- Nitrate/oxalate concerns
- Common in coastal areas
- Seeds in hay concern
- Very common
- Also drought stress risk
- Muscle damage, weakness
- Common weed
Regional Unique Concerns
- Hot summer months
- Rapid death possible
- Seeds toxic
- Common in rice country
Seasonal Risk Calendar - Gulf Coast
| Month | Primary Concerns |
|---|---|
| Jan-Feb | Flooding → future cocklebur risk |
| Mar-Apr | Cocklebur seedlings, spring flooding |
| May-Jun | Continued seedling risk, algae beginning |
| Jul-Aug | Blue-green algae peak, hot wet conditions |
| Sep-Oct | Hurricane debris (oleander), post-storm flooding |
| Nov-Dec | First frost risks (sorghum), hay quality |
Interactive Regional Features
Website Implementation
- Automatic content filtering based on selection
- Location-based mobile app functionality
- Regional alerts for seasonal risks
- Local extension office links
Regional Quiz Variations
- Quiz questions weighted by regional relevance
- Regional-specific photo sets
- Localized seasonal timing
Cross-Regional Summary Table
Plant Presence by Region
| Plant | High Plains | Rolling Plains | Cross Timbers | Piney Woods | Hill Country | South Texas | Trans-Pecos | Gulf Coast |
|---|---|---|---|---|---|---|---|---|
| Locoweed | ●●● | ●●● | ●● | ● | ●● | ● | ●●● | ● |
| Oak | ● | ●● | ●●● | ●●● | ●●● | ●● | ● | ●● |
| Oleander | ● | ●● | ●● | ●● | ●● | ●●● | ● | ●●● |
| Cocklebur | ●● | ●● | ●●● | ●●● | ●● | ●● | ● | ●●● |
| Perilla Mint | - | ● | ●● | ●●● | ● | - | - | ● |
| Lantana | ● | ●● | ●● | ●● | ●● | ●●● | ● | ●●● |
| Bitterweed | ●● | ●●● | ●● | ● | ●●● | ●● | ●● | ● |
| Water Hemlock | ● | ● | ●● | ●● | ●● | ● | ● | ●●● |
---
