Poison Hemlock

As I drive down the freeway, I am seeing Poison Hemlock everywhere. What’s a gardener to do?

Poison hemlock is currently in the growth stages in southern Ohio that are susceptible to early-season management options. Seeds have germinated and last season's rosettes are beginning to "bolt."  Eliminating these plants now can significantly reduce infestations.

Poison hemlock (Conium maculatum) is in full flower in much of Ohio with some plants showing signs of senescence in the southern part of the state meaning flowers are mature and seeds will soon follow. This means it’s too late to reduce the seed bank by targeting flowering plants with herbicides or mowing.

Poison hemlock and wild parsnip are currently in a growth stage that makes them susceptible to early-season management options. Targeting these dangerous plants now will prevent flowering and seed production.

Poison hemlock (Conium maculatum) is one of the deadliest plants in North America. Wild parsnip (Pastinaca sativa) sap can produce severe, painful skin blistering. Both are commonly found growing together in Ohio and both are beginning to bloom meaning the clock is quickly winding down for controlling these non-native nasties.

Poison hemlock and wild parsnip are currently in a growth stage that makes them susceptible to several management options. Targeting this stage for control will prevent flowering and seed production.

Poison hemlock (Conium maculatum) and wild parsnip (Pastinaca sativa) are two of our nastiest non-native weeds found in Ohio. Poison hemlock is one of the deadliest plants in North America. Wild parsnip can produce severe, painful blistering. Both are commonly found growing together.

Poison hemlock is a non-native biennial weed that spends its first year as a low-growing basal rosette; the stage that is currently very apparent. Targeting this stage for control will eliminate the first-year rosettes and prevent the development of the towering flowering stage.

Poison hemlock and wild parsnip are two of our nastiest non-native weeds found in Ohio. Poison hemlock can kill you while wild parsnip may make you wish you were dead. Both are commonly found growing together and continuously wet conditions caused both to flourish this growing season. The size of some infestations has been remarkable. Poison hemlock produces white flowers on stalks that create a more rounded look; perhaps a bit more like an umbrella.  Wild parsnip has intense yellow flowers with the stalks producing a more flat-topped appearance.

Second-year wild parsnip plants are producing deeply grooved flower stalks topped by characteristic bright yellow blooms in southern Ohio. Landscape managers and gardeners should exercise extreme caution around this non-native invasive biennial plant.