Texas Seasonal Poisoning Calendar: Year-Round Toxic Plant Awareness

Know When the Danger Is Coming

Knowing when toxic plants pose the greatest threat to your livestock is key to staying ahead of problems. This seasonal calendar lays out the primary poisoning risks throughout the year in Texas, so you can anticipate dangers and take action before you're dealing with a dead cow.

Texas's diverse climate zones — from the humid East Texas Piney Woods to the arid Trans-Pecos region — create varying risk periods, but general patterns apply statewide. Use this calendar as a practical reference tool for day-to-day ranch management.

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Quick Reference: Monthly Poisoning Risk Overview

January: Winter Vigilance

Risk Level: LOW to MODERATE

• Oak browse consumption during feed scarcity
• Nitrate accumulation in stored forages

• [ ] Inspect hay for mold and contamination
• [ ] Limit access to oak browse areas
• [ ] Ensure adequate quality feed to prevent hunger-driven toxicity
• [ ] Check water sources for ice damage and quality
• Freeze-thaw cycles can damage stored feeds
• Monitor for drought conditions affecting spring forage outlook

February: Early Spring Emergence

Risk Level: MODERATE

• Oak bud development
• Transitional feeding challenges

• [ ] Note oak catkin development stages
• [ ] Plan herbicide applications for early-emerging weeds
• [ ] Continue hay quality monitoring
• [ ] Begin planning for spring pasture management
• Panhandle: Still primarily hay-fed; focus on stored feed quality
• Hill Country: Watch for early larkspur and bitterweed

March: Spring Emergence Peak

Risk Level: HIGH

• Oak toxicity peak period begins
• Young, palatable toxic plants most dangerous

• [ ] Mark oak areas and consider temporary fencing
• [ ] Remove cattle from fields with dense cocklebur seedlings
• [ ] Apply herbicides to target locoweed and bitterweed
• [ ] Monitor hay fields for toxic weed emergence
• [ ] Begin supplemental feeding to reduce hunger grazing

April: Maximum Risk Period

Risk Level: VERY HIGH

• Oak poisoning peak
• Prussic acid in new sorghum-sudan grass growth
• Multiple toxic species actively growing

• [ ] Consider complete pasture rotation away from high-risk areas
• [ ] Do NOT graze new sorghum/sudan until 18-24 inches tall
• [ ] Conduct weekly toxic plant surveys
• [ ] Have activated charcoal and vet contacts ready
• [ ] Ensure adequate water to flush toxins
• [ ] Document any plant consumption incidents
• Activated charcoal (2 lb per adult cow)
• Veterinarian emergency contact
• Plant samples for identification
• Treatment protocols

May: Continued High Risk

Risk Level: HIGH

• Bitterweed peak in affected areas
• Transition to summer stress patterns
• Pre-drought toxin accumulation may begin

• [ ] Continue herbicide programs as needed
• [ ] Monitor bitterweed areas closely
• [ ] Begin hay field inspections for summer cutting
• [ ] Scout for developing weed populations
• [ ] Reduce locoweed access before seed set

June: Early Summer Stress

Risk Level: MODERATE to HIGH

• Nitrate accumulation in stressed forages
• Pigweed and amaranth establishment
• First hay cutting quality concerns

• [ ] Monitor pigweed populations in pastures and hay fields
• [ ] Don't graze stressed Johnson grass
• [ ] Ensure adequate water availability
• [ ] Plan hay cutting to avoid weed contamination
• [ ] Consider early weed removal in hay fields

July: Peak Summer Stress

Risk Level: HIGH

• Drought-induced toxin concentration
• Blister beetles in alfalfa and hay
• Overgrazing leading to toxic plant consumption

• [ ] Test all hay—especially alfalfa—for blister beetles
• [ ] Provide supplemental feed to prevent desperation grazing
• [ ] Ensure multiple clean water sources
• [ ] Avoid working cattle during extreme heat
• [ ] Scout for pigweed in hay fields before cutting

August: Late Summer Dangers

Risk Level: HIGH

• Perilla mint approaching peak toxicity
• Pigweed seed production
• Poor quality hay being fed due to scarcity

• [ ] Begin perilla mint awareness in shaded pastures
• [ ] Mow or spray pigweed before seed maturation
• [ ] Inspect all purchased hay thoroughly
• [ ] Prepare for fall acorn season
• [ ] Plan pasture rotations for September

September: Fall Transition Dangers

Risk Level: MODERATE to HIGH

• Perilla mint peak toxicity
• First frost risks for prussic acid
• Hay contamination from fall weeds

• [ ] Fence cattle out of perilla mint areas
• [ ] Don't graze sorghum/sudan after frost for 7-10 days
• [ ] Monitor first frost dates closely
• [ ] Scout hay fields before final cutting
• [ ] Consider acorn dilution strategies
• Do NOT graze sorghum/sudan/Johnson grass for 7-10 days
• Wait until plants are completely dry
• Test for prussic acid if concerned
• Hay from frosted fields should be tested or aged 6+ weeks

October: Acorn Toxicity Peak

Risk Level: HIGH

• Post-frost prussic acid risks
• Fall hay quality concerns
• Transition to winter feed programs

• [ ] Provide alternative feeds to reduce acorn consumption
• [ ] Don't let cattle fill up on acorns
• [ ] Continue frost protocols for susceptible forages
• [ ] Inspect fall hay cuttings carefully
• [ ] Remove cattle from areas with dense cocklebur seed

November: Post-Frost Management

Risk Level: MODERATE

• Frost-damaged plant cleanup
• Hay quality as primary feed begins
• Late fall toxic plant persistence

• [ ] Test winter hay supplies for nitrates and quality
• [ ] Clean up frost-damaged forage areas
• [ ] Plan winter feeding programs
• [ ] Scout for oak areas to avoid in spring
• [ ] Document this year's problem areas for next season

December: Winter Preparation

Risk Level: LOW to MODERATE

• Stored feed management
• Browse consumption during shortages
• Planning for spring prevention

• [ ] Establish hay feeding rotation plan
• [ ] Check all stored feeds for mold/contamination
• [ ] Plan spring pasture management
• [ ] Order herbicides for spring applications
• [ ] Review and update emergency protocols
• [ ] Schedule pre-calving nutrition programs

Downloadable Calendar Resources

Monthly Reminder Cards

Full-year visual calendar with risk levels and primary concerns:

Consider setting up calendar reminders:

• Monthly "toxic plant patrol" dates
• Frost alert responses
• Acorn season start/end
• Hay testing reminders

Regional Adjustments

East Texas (Piney Woods)

• Perilla mint risk: August-October (primary concern)
• Oak species: Multiple; extended toxicity periods
• Add: Pine needle toxicity for pregnant cattle

Central Texas (Hill Country)

• Oak toxicity: March-April peak
• Bitterweed: February-May primary risk
• Bladderpod: April-May

West Texas (Trans-Pecos)

• Locoweed: March-June primary season
• Broom snakeweed: Drought-dependent
• Rayless goldenrod: September-October

South Texas (Rio Grande Plains)

• Extended growing season = longer toxicity periods
• Lantana: Year-round concern
• Earlier spring emergence (adjust dates 2-4 weeks earlier)

Panhandle (High Plains)

• Shorter growing season
• Locoweed: Primary spring concern
• Stronger frost effects on sorghum
• Later spring emergence (adjust dates 2-4 weeks later)

Emergency Quick Reference

Poisoning Suspected - Immediate Actions:

• REMOVE animals from pasture/feed source
• CALL veterinarian immediately
• IDENTIFY suspected plant/feed
• SAVE samples (paper bag, refrigerate)
• DOCUMENT symptoms, timeline, affected animals
• ISOLATE remaining feed source

Emergency Contacts:

• Your veterinarian: _______________
• Texas A&M Veterinary Diagnostic Lab: (979) 845-3414
• USDA Veterinary Services: (844) 820-2234
• Poison Control (human exposure): (800) 222-1222

The Bottom Line on Seasonal Awareness

Seasonal awareness is your first line of defense against toxic plant poisoning. When you know the yearly cycle of risks and put preventive measures in place before problems hit, you can protect your livestock from losses that didn't have to happen.

Use this calendar as a working document — mark it up, add local observations, and adjust for your specific operation and region. The best ranchers anticipate problems rather than react to them.

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Related Resources

• 4.2.1 Spring Poisoning Risks
• 4.2.2 Summer Toxicity Watch
• 4.2.3 Fall Acorn and Frost Dangers
• 4.2.4 Winter Hay Contamination Risks
• 4.1 Complete Texas Toxic Plants Guide