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Be on the lookout for water hemlock

About 1-1/2 pounds of leaves or a bite of a bulb is enough to kill a cow

This Water Hemlock (above) looks similar to the harmless Water Parsnip, but it doesn’t take much of the leaves and only one tuber to kill a grazing animal.

You are typically hearing from me with an Australian story but for a change I am reporting to you from our 4-Clover Ranch south east of Rocky Mountain House, Alberta. Since coming back in late May we have endured a very dry spring and summer. While a good 125 mm of rain has fallen since mid-June many pastures have had a tough time catching up from a very poor start.

We decided to graze our semi-open woodlot and rely more on some lower ground not previously grazed much. So far it has turned out well. Our 2015 grazing data, which puts grazing days into a spreadsheet and calculates animal unit days per acre, will on some of our pastures, not look a whole lot different than 2014. This is especially true of the lower pastures which were skim-grazed early in June and have since banked a lot of reasonably good-quality forage for grazing late summer on the second rotation.

It hasn’t been without challenges and one of them, the grazing of the semi-open woodlot on the home place for the first time in about 10 years. We enjoy monitoring the cattle and the grass as they move through our 25 pastures and observing how the plants respond to the grazing management. It is gratifying seeing the species diversity expanding as some species thrive under different rest regimes. It is also pleasing to see weed species such as tall buttercup declining and our relying less and less on herbicides for control.

Hemlock concern

One species that caused some angst this year in grazing the woodlot was not your typical noxious weed but rather the native plant, Western Water Hemlock. As a native plant it is not regulated under the Weed Control Act but it is certainly an equally undesirable plant to that of tall buttercup and capable of causing significant and rather instant losses in the form of cattle deaths.

I just came in from a pasture check of the woodlot pasture and shuddered to find more than my liking of the extremely poisonous Western Water Hemlock. We previously haven’t seen many plants, but perhaps the dry year brought them on, especially seeing their preference for lower areas which this year have had better growing conditions overall. Exactly the areas we are relying more on grazing this year, not a good combination.

While herbicide control is an option in the early stages of growth with 2,4-D or glyphosate, the plants we found were mature. The soft ground where they grew made it relatively easy to pull them, which is the cause for concern as cattle will do that as well.

Western Water Hemlock has a unique and characteristic double-compound leaf. This means that aside from the main leaf stem’s leaflets, the lower part of the stem has additional compound leaves on each side of the main leaf stem. Once you train your eyes to this identifying characteristic you don’t have to physically touch the poisonous plant to look for the more common characteristic, the root tubers, which is where the bulk of the toxin is stored. There is another species called Water Parsnip that looks similar but it lacks the double compound leaf feature as well as the root tubers.

A lethal plant

While the poison is throughout the plant it is more concentrated in the tubers and the lower stalk, which is chambered near the base of the plant. When cutting the stem base and tubers in half lengthwise, a clear oily substance oozes out containing the cicutoxin poison. This quickly turns yellow upon exposure to the air. One tuber is enough to kill a 1,600-lb. cow. Green leaf material is fatal as well if consumed at a dose of 0.1 per cent of body weight (1.6 lbs. by the same cow). Other livestock and humans are affected as well and the most well-known connection would be that of Socrates sentenced to death by drinking hemlock juice in 399 BC.

We discovered with some concern that some of the plant had been slightly grazed prior to our discovery but not enough to see signs on the cattle such as trembling, salivation or worse yet, four legs pointing up to the sky. Two further checks of the woodlot tell me that we’ve got them and we shouldn’t have any cattle going the Socrates way.

Kim Nielsen provides an Australian perspective from time to time. He grows grass during the Australian summer at Alcheringa Pastoral in the South West of the state of Victoria, Australia and during the Canadian summer up on 4-Clover Ranch, Rocky Mountain House, Alberta.

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