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Winterizing, Seed Collecting, and Compost Contamination

bare tree branches in the woods as a small gray and white bird flies
Winter will be here soon. (Photo by: Ilze Long)

December in the garden is one of the slower months of the gardening year. This is the month to finish planting the spring-blooming bulbs and to quickly plant organic garlic cloves in the vegetable garden. I have a few woody plants to move around, which I will do before the end of the month.

With the patience of a seasoned gardener, I am waiting for the leaves to drop from two small Japanese maples (Acer palmatum) before I move them to new locations. I am moving the two apple trees I demonstrated fruit tree pruning on to my son-in-law and daughter’s house, replacing them with Asian Persimmon (Diospyros kaki) trees at my house. I am undertaking this swap out because I have decided to forego fighting Cedar Apple Rust, a fungal disease with a life cycle requiring two hosts Juniperus spp. (includes Eastern Red Cedars),  and Malus spp. (includes apple, crabapple, or hawthorn trees). The last plant move of the 2022 season will involve the small tart cherry tree, which is still green. I guess it missed the memo that fall will soon be slipping into winter.

I took advantage of a recent rainy day to sow my meadow with seeds collected from a friend’s native plant garden, a few from the wild and some I purchased from a native plant seed supplier. I am quite pleased with the mix of seeds I gathered over the past months, and I am looking forward to watching them grow and bloom. Starting from seed, this may take a few years but that’s the fun of it!

While I have finished winterizing the water spigots and have put away the water hoses, I still need to clean each tool of soil and debris. Before storing them in the shed, I wipe each tool down with a thin coat of oil to protect the metal against rust. I do not store my pruning shears in the shed — they belong in the house, and I always keep them sharp and clean. For power tool winterization, I am of the school to run the chainsaw, leaf blower, and any two-cycle engine dry to reduce corrosion from the moisture that condensates from the mixed gas. I take a few extra minutes to clean my outdoor power tools and to change the air filter before placing them in the shed. When the growing season starts up, I will use ethanol-free gas in these small engines to prevent the carburetor from gumming up.

After tending to the tools, I take time to review the garden and landscape photos I have taken over the past few months to assess the past growing season, and mentally establish a starting point for next year. Two fellow gardeners discovered the hard way their choice in compost products may have introduced a commonly-used broadleaf herbicide into their vegetable garden. While banned from use in residential applications, clopyralid is labeled for use in agriculture applications. This broadleaf herbicide is an auxin-mimic, which means it causes the plant to grow itself to death. This auxin mimic herbicide group is used by farmers to control pasture weeds that may harm their livestock.

Plant damage from clopyralid or similar herbicides may look like cupping or curling. Not all plants are affected, but many vegetables are. (Photo by: Oregon Department of Agriculture)

Per the National Pesticide Information Center, the residue of clopyralid and other pyridines, do not harm the livestock; however the herbicide passes through the digestive track and is excreted in the animal’s urine and manure. If the tainted manure or hay, which can be coated with the long-lasting residue, from a treated pasture is taken away, the herbicide residues go with it. The herbicide residues from this group do not break down during the composting process. This is referred to as "herbicide carryover." Depending on soil conditions, clopyralid may last for months to years in the soil. The healthier the soil, the faster the herbicide will be broken down by soil microbes like bacteria and fungi. However, here is the “But” — it takes time.

Both vegetable gardeners noted the areas where the purchased compost was incorporated into their garden. In both situations, the vegetable plants were either killed, distorted, or did not grow at all. While not toxic to humans, this Pyridine carboxylic acids group of broadleaf herbicides is toxic to many vegetables. In 2013, Virginia Tech wrote a paper on the herbicide group and the impacts on compost, if you are interested in going a little deeper into this topic.

To avoid the entire situation, purchase compost products with the USDA Organic Certification label on the package. This label proves the product has been reviewed and approved by a USDA-accredited certifying agent. This is the classic situation in which an ounce of prevention is worth a pound of cure.

I am looking forward to the slower months of the gardening year, but it truly never ends. Next month I will share tips on how to reduce insects and disease in your garden in the middle of winter.

Happy Gardening!
- Peggy Singlemann,  Landscape Consultant and Gardening Speaker