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Fall is Time for Garden Cleanup

Powdery mildew on a tomato plant. When cleaning out a vegetable garden, it is important to remove as much diseased plant material as possible. Tomatoes are notorious for getting late season fungal diseases, so as you remove tomato plants and cages, pick up as many fallen tomatoes and leaves as you can find. Photo courtesy of Cornell University.

Now that we’ve had a few frosts and the last carrots, Brussels sprouts, and spinach leaves are mostly harvested, it is important to shift focus from the growing season to garden cleanup.

Cleaning up the garden has many benefits ranging from keeping tomato cages rust-free, removing overwintering sites for plant pathogens and insects, making it easier to prepare the garden in the spring, and it just makes things look nice and tidy.

Different practices are used for different types of garden areas. In herbaceous flower beds, most foliage can be pulled out or cut back to ground level after the vegetation is dead. Some plants provide winter interest, so unless plants are diseased, these can remain standing. Come spring, just make sure to remove it before the plants start growing.

For woody perennials, leaf litter can be a major source of plant pathogens. Fungal pathogens overwinter on plant material so the more leaves/fruit that are left in the garden, the higher the potential fungal pathogen population the following season. Diseased tree leaves, for example apple leaves (and fruit) that had apple scab, should be gathered as thoroughly as possible and destroyed.

For most woody perennials, it is best to wait to prune until late winter, except broken branches can be removed at any time. Spring-flowering shrubs, like lilac bushes, set buds in the summer. Those bushes should not be pruned in the winter, but rather right after they are done flowering. To minimize some of the winter burn we saw on conifer trees this year, make sure trees get about one inch of water from either rain or irrigation per week until the ground freezes.

When cleaning out a vegetable garden, similar to other areas, it is important to remove as much diseased plant material as possible. Tomatoes are notorious for getting late season fungal diseases, so as you remove tomato plants and cages, pick up as many fallen tomatoes and leaves as you can find. The same concept holds true for squash or other plants that have powdery mildew.

Plant material pulled out from garden beds can be disposed of by composting at either a municipal site or in a private bin, burying it, or burning it (when allowed). When composting plant material, it is essential that the compost pile is properly managed so the pile heats up to temperatures above approximately 130°F to kill most weed seeds and pathogens. Ensuring that the pile is turned regularly to allow for sufficient airflow, it stays moist, and that there is a balanced diet of “greens” (vegetable scraps, living plant material, etc.) and “browns” (dead leaves, twigs, etc.) to feed the microbes that decompose the pile, will help it reach those high temperatures.

Leaving garden beds completely bare can lead to potential erosion and soil loss, especially in the spring when the snow starts to melt. A great alternative to bare soil is to plant a cover crop. Cover crops are plants that are specifically grown to protect and improve the soil, but not intended for harvest. Ideal cover crop mixes will vary in each situation and there is significant research going into determining recommendations. Some common species used for cover crops include different grasses (rye, wheat, barley, oats, triticale), brassicas (forage radishes, turnips), and legumes (clovers, vetch), to name a few. Each species can have substantial positives and negatives.

For gardeners who just want to try it out, annual rye grass is a good option for this time of year. It can be successfully planted until the snow flies. Rye grass will survive the winter and begin growing again in the spring, protecting the soil when it is most vulnerable to erosion. If rototilled before it is four inches tall, rye grass should be killed in time for you to plant vegetables or flowers without it becoming a weed. If you are skeptical, try planting a cover crop in just one garden bed and see how it goes!   

With proper diligence and a little hard work, these sunny, cold fall days can be used to help set you up for a great garden next year.

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