Nightshade Species on Texas Ranches

The Nightshade Family: Common, Widespread, and Dangerous

The nightshade family (Solanaceae) includes some of the most common toxic plants found on Texas ranches. While the family also includes useful plants like tomatoes and potatoes, several wild species pose serious threats to cattle. Nightshades show up throughout Texas in all kinds of habitats, from disturbed soils to well-established pastures.

This article covers identification of the major nightshade species in Texas, their toxic properties, and management strategies to protect your herd.

---

Understanding Nightshade Toxicity

The Toxins: Glycoalkaloids

Nightshades contain solanine and related glycoalkaloids—compounds that affect the nervous system and gastrointestinal tract.

• Disrupt nerve impulse transmission
• Can cause respiratory paralysis
• Affect heart rhythm at high doses

Toxicity Characteristics

Lethal Doses

Estimated lethal doses vary by species and animal condition:

• Silverleaf nightshade: 0.1-0.3% of body weight (1-3 lbs for 1,000 lb cow)
• Buffalo bur: Similar toxicity
• Black nightshade: Slightly less toxic, but still dangerous

Major Nightshade Species in Texas

Silverleaf Nightshade (Solanum elaeagnifolium)

• Silvery-green leaves covered with star-shaped hairs
• Wavy leaf margins (not smooth)
• Purple to lavender star-shaped flowers with yellow centers
• Yellow to orange berries when ripe (start green)
• Thorny stems in some populations
• Deep root system (very hard to eliminate)
• Overgrazed pastures
• Field margins
• Urban fence lines
• Sandy to clay soils
• Deep roots make control difficult
• Spreads by both seed and root fragments
• Persistent in improved pastures

Buffalo Bur (Solanum rostratum)

• Covered with yellow prickles/spines on stems and leaves
• Deeply lobed leaves (almost fern-like)
• Bright yellow flowers (unlike most nightshades)
• Spiny bur-like fruit
• Very unpleasant to handle
• Waste ground
• Corrals and high-traffic areas
• Roadsides
• Sandy soils
• Cattle usually avoid due to spines, but consumption occurs in hay

Black Nightshade (Solanum americanum/nigrum complex)

• Oval leaves with wavy margins
• Small white flowers in clusters
• Berries that ripen from green to shiny black
• Smooth stems (no thorns)
• Crushed leaves have distinctive odor
• Moist, rich soils
• Shaded areas
• Near water sources
• Disturbed ground
• Ripe black berries are less toxic but still harmful in quantity

Horse Nettle (Solanum carolinense)

• Thorns on stems and leaf midribs
• Lobed leaves
• White to pale purple flowers
• Yellow berries when ripe
• Pastures with history of cultivation
• Sandy soils

Comparison Chart

Signs of Nightshade Poisoning

Clinical Progression

• Loss of appetite
• Depression
• Dilated pupils
• Weakness
• Staggering
• Muscle tremors
• Labored breathing
• Collapse
• Rapid, weak pulse
• Convulsions
• Coma

Post-Mortem Findings

Veterinary examination may reveal:

• Inflammation of digestive tract
• Hemorrhaging in intestines
• Congested organs
• Often limited specific findings

When Nightshades Become Dangerous

High-Risk Scenarios

• Wilted plants retain toxicity
• Cattle that ignored plants before may consume after frost
• Hay from weedy fields is risky
• Buffalo bur particularly common in hay
• Cattle forced to eat available plants
• Stress may increase plant toxicity
• Nightshades often thrive where grass is weakened
• Cattle have fewer options
• Local cattle may have learned to avoid

Prevention Strategies

Pasture Management

• Healthy grass competes with nightshades
• Proper stocking rates reduce nightshade density
• Minimize tillage in pastures
• Manage traffic patterns

Herbicide Control

|-----------|------|-------| | Picloram + 2,4-D | Per label | Most effective on silverleaf | | Dicamba | 0.5-1 lb/acre | Good on annuals | | 2,4-D | 1-2 lb/acre | Suppression only | | Aminopyralid | Per label | Selective | | Metsulfuron | Per label | Add surfactant |

• Early treatment (before seed set) reduces spread
• Silverleaf may require repeated treatments due to deep roots
• Fall applications can be effective

Mechanical Control

• Does not eliminate perennials
• Best combined with herbicide
• Must remove roots of perennials
• Labor-intensive
• May help control annuals if repeated
• Generally not recommended in established pastures

Hay Management

• Treat problem areas before hay cutting
• Avoid baling heavily infested areas
• Reject suspicious bales
• Know your hay source

Treatment for Poisoning

Immediate Actions

• Remove from pasture - Prevent further consumption
• Call veterinarian - No specific antidote; supportive care needed
• Provide fresh water - Critical for diarrhea cases
• Keep cattle calm - Stress worsens outcome

Veterinary Treatment

May include:

• Activated charcoal (if caught early)
• IV fluids for dehydration
• Respiratory support
• Symptomatic treatment
• Close monitoring

Prognosis

• Mild cases: Good with supportive care
• Moderate cases: Fair, depends on amount consumed
• Severe cases: Poor, especially once paralysis develops

Buffalo Bur in Hay: Special Concern

Buffalo bur is commonly found contaminating hay, particularly from weedy fields or drought years.

Why It's a Problem in Hay

• Spines become brittle when dry—less protective for plant
• Cattle may consume when mixed with hay
• Toxicity is retained
• Difficult to see mixed with other material

Inspection Tips

• Look for distinctive spiny burs
• Check for yellow-brown dried plants
• Break apart suspicious bales
• Reject bales with significant contamination

What to Do If Found

• Don't feed contaminated hay
• Inform supplier
• Consider returning shipment
• Monitor any cattle that may have consumed

Regional Considerations

South Texas

• Silverleaf nightshade abundant year-round
• Mild winters allow early growth
• Watch for consumption during late winter dry periods

Central Texas

• Black nightshade common in valleys and creek bottoms
• Silverleaf in uplands
• Fall frost triggers risk period

Panhandle/West Texas

• Buffalo bur common in disturbed areas
• Silverleaf widespread
• Drought conditions increase risk

East Texas

• Black nightshade in moist areas
• Horse nettle in sandy soils
• Hay contamination concern

Integration with RanchGuard Monitoring

Future monitoring technology could help with nightshade management:

• Alerts when cattle concentrate near known nightshade areas
• Tracking consumption patterns that might indicate poisoning risk
• Documentation of plant locations for treatment planning

Bottom Line

• Silverleaf nightshade is ubiquitous - Learn to recognize it; it's probably on your ranch
• Green berries are most toxic - But all parts are dangerous
• Frost increases palatability - Watch consumption after first frost
• Hay can kill - Buffalo bur and other nightshades in hay are serious risks
• Control is ongoing - Silverleaf's deep roots make eradication nearly impossible; manage the population
• Good grass management is prevention - Healthy pastures resist nightshade invasion
• No antidote exists - Focus on prevention; treatment is supportive only
• Watch for symptoms - Drooling, diarrhea, and weakness warrant immediate investigation

Related Resources

• Complete Guide to Texas Toxic Plants
• Drought and Increased Toxicity
• Hay Quality Inspection Checklist
• Pasture Walk Inspection Guide

References

• Texas A&M AgriLife Extension. (2024). "Nightshade Poisoning in Cattle."
• Burrows, G.E. & Tyrl, R.J. (2013). Toxic Plants of North America. Wiley-Blackwell.
• Knight, A.P. (2001). A Guide to Plant Poisoning of Animals in North America. Teton NewMedia.
• USDA NRCS Plants Database. (2024). Solanum species profiles.
• Reagor, J.C. (1995). "Solanine Poisoning in Texas Cattle." Texas Veterinary Medical Diagnostic Laboratory.
• McGinty, A. & Ueckert, D.N. (2001). "Brush Busters: How to Control Silverleaf Nightshade." Texas A&M Publication L-5468.

"The nightshade that grows by the fence can kill what grazes behind it"