Poisonous Hemlock: A Growing Problem

The association of poison hemlock with the death of Socrates in ancient Greece in 399 B.C. provides a glimpse of the toxic history of this plant. Two decades ago an aggressive search was required before a specimen could be found in Arkansas, but now poison hemlock grows abundantly within a stones throw of anywhere.

A close relative of carrot, celery, dill, and Queen Anne's lace, hemlock has found a seat in the front row due to its association. Unlike most of its relatives, however, all parts of the hemlock plant are considered toxic to people, as noted in Greek history, and to livestock.

Fortunately, animals seem to be smart enough to avoid hemlock, at least while pastures are supplying other desirable forage. Producers are yet to report that animals have grazed hemlock, and area veterinarians report minimal, if any livestock health issues. Overgrazing is a pattern that will force animals to eat what they know not to consume.

It appears logical that hemlock, due to its abundance in fields, could be caught up in the haying process after which livestock would eat parts of the plant, even if by accident.

The lethal dose for cattle, which is less than for horses, is reported to be from 2 - 5 pounds per 1,000 pounds of body weight. That may be one reason for the lack of death losses since a lethal dose would require a fair amount of intake and hemlock doesn’t appear to be a forage plant to whet the appetite.

Hidden losses may be the major concern, similar to those caused by nitrate poisoning. Low levels of many toxins cause weight, milk, birth defects and other livestock production losses before death enters the picture, if ever. As in the case of nitrate issues, hemlock problems are possibly being blamed on other causes.

Hemlock may take the place of thistle as the primary weed of concern. Unlike thistle, hemlock seeds aren’t carried by the wind to infest neighboring fields. Water, birds and equipment are possible carriers, but most hemlock seed drop near the parent plant and emerge on site. Like thistle, hemlock continues to reproduce abundantly on the increasing acreage of non-farm land.

You can't help but notice new hemlock seedlings since they are fairly cold tolerant and, beginning in February, provide the first green, fern-like foliage to dress road right-of-ways, fence rows and creek bottoms. The 6- to 8-foot mature plants continue to remind us all summer.

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