Under the Cover of Green Manure

We’re all familiar with that wonderful brown substance we call manure, or, as I prefer to call it, “fruit of the butt.” Manure is a rich source of nitrogen for our growing plants, and it can also serve as a mulch. Yes, without manure, life would be pretty sh…, well, you get the idea.

Now, I’d like to introduce you to a different kind of manure. This kind does not come from a bovine or equine backside, but it grows right out of the soil. These are various plants known collectively as cover crops or green manure. Green manure plants are grown for the sole purpose of being killed by cold weather, chopped up, and worked into the soil. Like the other kind of manure, it provides nitrogen, but it does a whole lot more. Green manure crops can crowd out weeds, reduce soil erosion, and improve the overall condition of the soil.

Green manure crops are generally planted in late summer or early fall, then chopped up and worked into the soil in the early spring. Alternatively, they can also be planted in spring or summer, and then tilled into the soil before planting a vegetable crop. They can also be planted in place of a vegetable crop and then worked into the soil to condition it for the following year’s crops.

Green manure crops consist of both legume and non-legume plants. Legumes such as field peas or vetch are planted for their nitrogen-fixing ability while non-legumes – grain crops like rye or wheat are planted for their ability to crowd out weeds. A wide variety of plants can be used as green manure crops. The table below lists some common ones.

The University of Wisconsin Horticulture, Division of Extension gives these instructions for planting. To plant a cover crop or green manure, first clear the planting area of any large stones and other debris.  Rake the area smooth and broadcast seed according to the seeding rate given in Table 1 or as recommended by the seed provider.  Rake the area again to incorporate the seeds into the soil, and lightly water the area. To prevent the cover crop from self-seeding in other areas of your garden, and to utilize the cover crop to its fullest potential, cut down plants when, or just before, they start to flower.  You can cut plants by hand, or by using a trimmer, brush cutter, or mower.  Cutting before flowering not only prevents the cover crop from going to seed, but also stops the plant from taking up nutrients from the soil to store in its seed.  Once plants have been cut, incorporate the plants into the soil (using a shovel, pitch fork or rototiller) where they can more readily decompose.  Allow approximately two to three weeks for the cover crop to decompose before planting your vegetables into the soil. (Source: University of Wisconsin Horticulture, Division of Extension)

So if you are looking for a way to improve the condition of your soil, and the brown manure isn’t doing the job, then why not try the green?

How Do I Know Which Mushrooms to Grow?

So you’ve decided to grow your own mushrooms. Congratulations! Mushroom growing is a wonderful hobby, and like gardening, there is a certain feeling of pride that comes with producing your own fungal treasures.

But now comes an important question – where do I begin? Just like when you were a beginning gardener, you should start with something easy. Once you’ve mastered coaxing a decent yield out of the substrate of an easy-to-grow species, then you can move onto something more challenging. But which species are easiest to grow? And what other factors are there to consider?

Some species require a great deal of maintenance, and thus should be avoided by the beginner. Maitake or hen of the woods, for example, requires a cold shock, 10-20oF (5.6-11oC), followed by a period of initiation under high carbon dioxide and humidity, and then followed by a high dose of oxygen. It can be tricky to create all of those conditions, not to mention the expense required to procure all the right equipment to make it all happen. So maitake mushrooms should probably be avoided by the beginning grower. On the other hand, oyster mushrooms are very easy to grow – indeed you can purchase specialized kits that require you to put in no more effort than slitting the side of a box and keeping it moist for a week or so, resulting in a quick yield of some tasty mushrooms.

Here are some other factors to consider.

Ease of identification – how easily you can tell your cultivated mushrooms apart from “weed” fungi. This is more of a factor with mushrooms grown outdoors on wood chips.

Substrate specificity – what kind of medium is required to grow a particular mushroom. Oyster mushrooms, for example, will grow on a wide variety of substrates — wheat straw, coffee grounds, hardwood conifers, agriculture waste, etc., all things that are fairly easy to obtain. Your local bakery would probably more than happy to give you all of their food waste that you can handle, and your oyster mushrooms will be perfectly happy growing on it. Maitake, on the other hand, will grow only on oak logs or oak wood chips. To be sure, you can get wood chips from a nursery, but they probably won’t be oak.

Temperature range and sensitivity – Just as you would not attempt to grow a plant from USDA Hardiness Zone 10 (average annual low 40oF-30oF) in Zone 6 (average annual low 0oF-minus 10oF), you would want to make sure that the mushroom species you wish to grow can survive the climate in your area. So if you live in the Chicago area, with that Zone 6 average annual low, then a hairy panus mushroom, which grows at tropical temperatures of 86-100+oF, would not be a good species to start with. Instead, try a shiitake or an oyster.

Time to maturation and yield – Some mushroom species are slow to produce, while others will fruit quickly. If you’re the impatient type, then you probably don’t want to start with truffles (10 years) or even king stropharia (4-6 months). Oysters take only about 10 days to produce.

Infrastructure – If you choose to start from scratch instead of growing from a kit, your choice of what to grow will be limited by the amount of physical space you have and substrates available to you. If logs and tree debris are all that you can get, then you will be limited to shiitake and whatever else grows on logs. If you can obtain wood chips from your local arborist, then you can grow king stropharia. If you can spare an extra room, such as a bathroom or closet, then you can have an indoor growing operation, using those extra rooms for colonization and fruiting.

So start with easy to grow species right for your climate on whatever substrate you can easily obtain, and will have improved the odds that you will get a bountiful harvest of delicious and nutritious mushrooms.