Going green...with manure?

During these seemingly endless, frigid days it is easy to pass by the Victory Garden outside of the museum’s Stars & Stripes Cafe and think that nothing’s happening. There are no bright colors, no vegetables, nothing to take notice of. To the contrary—the garden is in full swing!

When you look out the cafe window, it looks as if our lawn mower has broken and the grass has grown to almost a foot in areas. The overgrown “grass” is actually winter rye, a cover crop that we planted in October and will be using as a green manure. Okay, so what is a green manure? It may sound like a Dr. Seuss meal gone bad, but it’s actually an environmentally friendly and sustainable product that incorporates the benefits of one season’s crop into the needs of the next. In short, green manure is a natural fertilizer.

Green manure Green manure

Here’s how green manure works: The winter rye cover crop in the Victory Garden helps protect against erosion, retain nutrients that might otherwise be leached from the soil, suppress the germination and growth of weeds, cycle nutrients from the lower to the upper layers of the soil, and—in the case of legumes—leave to the following crop a considerable quantity of nitrogen. There are still more contributions of green manure: improved soil structure, additional organic matter, enhanced drought tolerance, and increased nutrient availability for plants. 

Wow! Sounds like a great deal (and it is), but don’t go into the shed tomorrow and throw out all of your fertilizers. Green manure is just one way of contributing to the health of your soil.

Although there are many cover crops to pick from, winter rye is a good choice because of its resistance to the cold temperatures. It also creates a lot of biomass, which increases the organic matter. Sow winter rye in September or October, depending on what growing zone you’re in, and leave it alone. It practically does all of the work on its own. In late March, the winter rye in the Victory Garden will be incorporated into the soil to start the decomposition dance. When the soil warms up enough, all of the millions of micro-organisms will awaken to begin breaking down the cover crop, forming a rich, dark, and spongy soil that the plants will be itching to sink their roots into. It will become green manure!

So, next fall, instead of leaving the soil bare after the vegetable plants are pulled, try planting a cover crop and make next year’s harvest even better. To learn more about cover crops, their time of planting, and their benefits, visit the USDA Alternative Farming Systems Information Center. Happy gardening!

Joe Brunetti is a Smithsonian horticulturalist for the National Museum of American History.