My Take on Cover crops

Cover crops (AKA green manures, AKA living manures) seem to be all the rage these days. But what are cover crops, how do they work, and are they practical for the home gardener?

There is a lot of talk about cover crops in the gardening world. It is certainly the case that their use is well established in the agricultural world, and has been for hundreds of years - but how practical are they for the home gardener?

What are cover crops?

Cover crops are typically grown in the off-season, or during fallow periods, and as the name suggests, are grown to cover and protect soil. The practice of planting cover crops goes back hundreds of years and evidence of their use can be found in ancient Rome and China. Today they are sometimes referred to as a “green manure” or a “living mulch” - but those are all just catchy new terms for cover crops. Typical cover crops are legumes, grasses or buckwheat¹.

This winter rye was planted in late September. It germinated quickly and stayed green all winter long.

What are the benefits of cover crops?

Cover crops generally enhance soil health in a number of ways. Some sources on the internet list dozens of benefits - but I think most are over-hyped, and marginal at best. For me, the main benefits of cover crops are the following:

1. Nitrogen Fixers: Legumes like vetch, clover, beans and peas, have the ability to fix nitrogen from the atmosphere into the soil. Most plants must pull nitrogen out of the soil to grow, but legumes are unique because they have a symbiotic relationship with bacteria that live in the soil. The bacteria attach themselves to the roots of the legumes to steal sugars from the plants. While they are doing this, the bacteria also pull nitrogen out of the air (the air in the soil) and make it available to the plants. When done properly, this results in a net increase of nitrogen in the soil.