The straight poop: Horse manure passes toxicology test

Lee pruning in the snow (Lee Reich)

Lee pruning in the snow (Lee Reich)

A dark cloud no longer hangs over my horse manure – that is, the horse manure that I occasionally truck over here to add to my compost piles. I wrote a few weeks ago about the possibility of herbicide that, when applied to hay, retains its toxic effect when an animal eats the hay and even for a long time after that animal’s manure has been composted or spread on the ground.

My herbicide residue concerns were soothed with a simple assay that showed satisfactory growth from bean seeds in both hay that was suspect and hay of known integrity. Also, the bedding in the horse manure is mostly wood shavings, rather than hay.

But another ugly dragon kept raising its head above the manure: another chemical, this time Ivermectin, a deworming medication given to horses (and other animals). Ivermectin or its metabolites might pass through the animal and injure soil-dwelling creatures such as beneficial nematodes and earthworms. Past studies have shown negative effects on, for example, “dung fauna and degradation of faeces” (to quote a research paper from 2006).

Ivermectin is, admittedly, a very useful material – even useful in humans to combat lice, bedbugs and some more frightening tropical afflictions such as river blindness and elephantiasis. Agriculture is always a balancing act, but I like to keep my soil-dwelling partners happy.

So I was gladdened when a veterinarian recently directed me to a Stanford University publication that summarized research findings on the environmental effects of Ivermectin. To wit: Ivermectin is excreted, and it can affect earthworms, springtails and other fauna. But it degrades quickly at summer temperatures (one to two weeks, but much longer in winter) and within a day or two of exposure to bright sunlight. With temperatures within my compost bins reaching 150 degrees Fahrenheit or more, with the compost sitting many months before use and with the compost being spread on top of the ground, little Ivermectin would end up in the soil. And soil naturally has low levels of this compound, anyway.

Let’s look aboveground, at stems; there’s pruning to be started. With well over a foot of snow on the ground, I turn my attention to taller plants. The snow is actually an advantage, because with snowshoes on, I can reach more than a foot higher into the branches without a ladder.

For now, I’m going to start with the easiest pruning, mostly with plants that don’t need regular pruning beyond removing dead, diseased, broken and grossly misplaced branches. Right here, such plants include pawpaws, plums, cornelian cherries and a teenage honey locust tree. Light is important for fruit production from the fruit trees and, generally, to keep diseases and insects at bay, so I also prune away enough branches to let remaining branches bathe in sunlight.

I go at the pawpaws with one more goal in mind: to keep fruit from forming either too high in the tree or too far out on the limbs. Pawpaw trees will grow 15 to 25 feet high, but I harvest fallen fruit from the ground. By my estimation, fruit can make a soft landing, undamaged, from a height of about ten feet onto mulched ground. So I lop back the tops to weak side branches at about that height.

Each pawpaw flower is a multiple ovary, potentially spawning up to nine fruits, each of which can weigh more than half a pound. That’s a lot of weight perched onto the end of a branch, so I shorten long branches to decrease leverage of that fruit load. (More about all types of pruning of all kinds of plants in my book, The Pruning Book.)

I actually did begin pruning a few weeks ago, before the first snowfall. The plant was hydrangea – no, not the common bigleaf hydrangea, which has many people scratching their heads about how to prune, but climbing hydrangea (Hydrangea anomala subsp. petiolaris).

Climbing hydrangea is one of the most beautiful vines, even right now as the peeling pale-cinnamon bark is in focus among the leafless stems. All summer long, the stems are clothed in lustrous green foliage, and in early summer, clusters of white flowers twinkle against that backdrop like stars in the dark sky.

As expected, the vine took a few years to get firmly established. Now it threatens to engulf my brick home – except that I want to restrict it to only the north wall. Every year now, I prune back stems creeping like groping fingers around the east and west walls. And each year the flower stems reach further directly out from the wall, so I also shortened them.

The present pruning doesn’t permanently subdue the plant. This summer, I’ll again shorten the wandering stems, and I’ll be back at it again next winter and for winters to come.

Join Cornell Cooperative Extension of Ulster County (CCEUC)’s master gardeners for their annual bus trip to the best flower show in the east – the Philadelphia Flower Show – on Thursday, March 5. For more information and full details on the 2015 Philadelphia Flower Show, visit it online at Buses will load at 6:45 a.m. and leave from the MAC Fitness parking lot, located in the Kingston Plaza, at 7 a.m. and will return at approximately 9:30 p.m. The New Paltz bus will load at 7:15 a.m. at the New York State Thruway Park and Ride, located at Exit 18 in New Paltz.

The cost is $70 per person, which includes transportation and show admission. Completed registration forms, available at, with payment must be received by mail no later than Friday, February 27 and can also be dropped off at the CCEUC Education Center, located at 232 Plaza Road in Kingston. For more information or help registering, call Carrie at (845) 340-3990, extension 311, or e-mail [email protected].


Any gardening questions? E-mail Lee at [email protected] and he’ll try answering them directly or in his Almanac Weekly column. To read Lee’s previous “Gardener’s Notebook” columns, visit our website at



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