10 Toxic Plants Hiding in Texas Hill Country Pastures

Overgrazed pastures are the biggest risk factor for plant poisoning — hungry animals eat things they'd normally walk past. A slow walk of your fence lines and any bare or overgrazed corners once a season catches most problems before they catch your livestock.

Bracken fern and horsetail cause thiamine deficiency in horses over time with sustained grazing. Cherry and oak (especially budding oak leaves and acorns in a wet spring) are two of the more common culprits we see in both horses and cattle in this region.

Sorghum-sudangrass hybrids and Johnsongrass carry a real risk of prussic acid (cyanide) poisoning after a frost or drought stress — if you graze these forages, know the danger window and hold animals off for the recommended period after any stress event.

Nightshade species and pigweed (redroot pigweed especially, linked to kidney failure in cattle) tend to show up in disturbed soil around gates, feeders, and overgrazed loafing areas rather than in healthy stands of grass — another reason good pasture management doubles as poisoning prevention.

If you're not sure what's growing in a problem spot, take a photo or bring in a cutting on your next visit. It's a much easier conversation before an animal gets sick than after.