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Don’t take water hemlock for granted

One of the challenges is to identify if the weed growing in your pasture or hayland is poisonous water hemlock (shown here) or harmless water parsnip (shown below). These plates show one difference, in the bracts found below the seed head. If still in doubt, it may be wise to consult a weed or forage specialist.

Water hemlock is popping up all over this summer. The fact that this weed is spreading on high ground had us hopeful any new growth we saw might be the harmless cow parsnips. However, the weed specialist confirmed the new growth as water hemlock on all our hayfields, now there is more than a little cause for concern.

Control is now the focus. During the 1940s, farmers were told as long as the cattle didn’t eat the root of the highly poisonous water hemlock there wasn’t a problem. Since then it has been proven that the toxin is in all parts of the plant, and grazing young plants can cause birth defects, miscarriages, open cows and death.

The birth defects in unborn calves that can result from the cow ingesting poison hemlock may include crooked legs (crooked calf disease, arthrogryposis), cleft palate, and kinked tails. Arthrogryposis means the permanent fixation of a joint in a contracted position. This is a congenital disorder, not due to a nutritional issue, and is marked by generalized stiffness of the joints, often accompanied by muscle and nerve degeneration, resulting in severely impaired mobility of the limbs. Arthrogrypotic skeletal malformations occur in calves when pregnant cows between 40 to 70 days of gestation ingest water hemlock.

Considering a cow can die from ingesting one water hemlock root, the assumption is that it wouldn’t need to eat much to cause these birth defects. The plant is poisonous to all livestock and the oils from the plant are very toxic to humans as well. This plant needs to be handled properly and with respect given to its ability to harm, as we found out last fall.

Respect the weed

My son was haying a field where at first there were just a few plants here and there. He just kept getting off the tractor and hand-roguing them. By the end of the day he would feel unwell but it would go away.

We have been told in the fall the poison goes to the root and the plants dry quickly, which is what they appear to be doing. The third day he found a fairly heavy infestation and started pulling those plants. He soon started feeling unwell again and this time his heart developed an irregular beat. Then he realized what the problem was. He wasn’t wearing gloves and he was feeling the effects of hemlock poisoning. Thankfully it wasn’t enough to be deadly but it was enough to scare us into respecting this plant. Although hand-roguing was an effective way of eradicating small outbreaks, it must be done safely.

Proper handling practices

Safe handling procedures for water hemlock would be similar to the safety protocols for handling other toxic substances such as pesticides. Since we had a scare we recommend following these step stringently. These guidelines were provided by a weed specialist for us to use.

1. Coveralls — preferably disposable water-repellent ones like Tyvek so that they can just be packed into a garbage bag and thrown away. If using fabric coveralls, wash them separately from other clothing. Use hot water and detergent, repeat wash once. Dry coveralls on a clothesline so as not to contaminate the dryer and allowing the sun to further decontaminate them. Clean the washing machine by running it through another wash cycle with only hot water and detergent.

2. Impervious gloves, either neoprene or nitrile material — long enough to cover your wrist and extend over the sleeve of your coveralls. Wash gloves with hot, soapy water, or dispose of gloves in a garbage bag once finished handling the hemlock.

3. Rubber boots — wash down with hot, soapy water after leaving the infestation site.

4. Protective eyewear — Safety glasses or goggles give protection against flying debris and help prevent the inadvertent rubbing of the eye while wearing contaminated gloves. These should also be washed with hot, soapy water once handling is complete.

5. Have a supply of clean water and soap available for immediate washing if there is any skin contact with the hemlock.

6. Do not eat, drink, smoke, or use the washroom until after you have thoroughly washed with soap and water. The oils from this plant are very toxic, and readily absorb through the skin.

7. In Ontario the crews that are involved in eradication programs are also cleaning their equipment so as to not contaminate fresh fields. This practice could be considered if cutting down big patches of water hemlock with haying equipment. The oils stick to the cutters and can then be spread over good feed.

8. Carefully gather all plant pieces and dispose of them in the garbage. If plants and roots are grubbed out of areas with standing water, animals should be excluded from the area to prevent them from drinking the contaminated water.

How to control

Our pastures have not been contaminated, but hay can be, and has. We are confused about how to manage the weed since one plant can produce 30,000 seeds that remain viable for three to six years, but at the same time it can reproduce by both root pieces and seed.

The recommendation from specialists is to plow the weed under this fall so the plants rot and you bury the seed. At this time of year it is clearly visible due to the white flowers/seed heads and it is quite tall. Then in the spring, once the area greens up, we are supposed to disc it lightly. The idea is to kill what might have grown without disturbing seeds, which should be far enough underground as to not germinate. Then they said to reseed the area to grass hay. There are chemicals that can be used against water hemlock with grass hay, but spraying is ineffective and costly.

So, for now, our plan is to do mechanical control along with increasing fertility of the land. We have to decide what forage species to plant so it will compete with the water hemlock. To be honest, we are very open to ideas so please send an email with suggestions.


30. Parsnip with bracts .jpg


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