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Biomass: Your Homegrown Resource for Rich Soil

Amelia has been an avid gardener since childhood and enjoys experimenting with natural and sustainable gardening methods.

Horseradish is a deep-rooted, easy-to-grow mineral accumulator.

Horseradish is a deep-rooted, easy-to-grow mineral accumulator.

Biomass in Permaculture

Soil is the basis for permaculture. It is where life begins. The most important activities in permaculture revolve around the soil. So, what is the key? Biomass. Biomass is the organic matter that becomes soil. It is the nourishment for the soil life that creates the soil.

Any heathy plant can be used. This sage is out of hand and about to become mulch for the almond tree.

Any heathy plant can be used. This sage is out of hand and about to become mulch for the almond tree.

What Is Biomass?

In permaculture, biomass is organic matter harvested for the purpose of creating soil. Green material and brown material are both beneficial for soil building and serve different purposes. Green matter is important for adding nitrogen to the soil, whereas brown matter is higher in carbon. Both are important for soil health, and a balance of the two encourages the breakdown of both.

How to Create Biomass

Once established, your forest garden will likely create huge amounts of biomass. You may be astounded at the quantity. It’s really remarkable what can happen when leaves photosynthesize carbon dioxide and water into the building blocks of new stems and leaves. My edible front yard is now in its third season and already producing armloads of biomass. The key to creating large amounts of biomass is growing perennials. Once established, perennials produce biomass constantly. Take comfrey, for example. Probably few other plants can beat comfrey for producing biomass. In its second year, comfrey will shoot up to three feet tall in the first few weeks of spring. Pollinators love it, so don’t chop it down right away, but when it starts to fall over is a great time to chop and drop. This same plant can be chopped down at least three (and up to seven) more times in the same season!

When you chop and drop plants, you actually prune not only what you see, but also what is hidden within the soil. Each time part of the plant is pruned, part of the root dies, creating humus and air pockets. The humus later feeds other plants, while the air pockets allow great permeation of water. This is important when biomass crops are planted among other crops: chopping and dropping these regularly reduces root competition and further nourishes the other crops.

Planning Your Garden

When planning your forest garden, biomass crops should make up at least a quarter of your garden. This can be done in one of two ways, or in a combination of both. An area can be set aside for biomass crops, or they can be distributed around the garden. I do both. I have an area that is dedicated to comfrey in front of my patio, but I also have comfrey, herbs, and nitrogen fixers distributed throughout the garden. I also have three mature trees on the property.

For a great idea for a dedicated biomass crop, see Biomass Belt. This is great if you want to create biomass for your annual garden. However, if you want to incorporate biomass crops into your forest garden, simply make space for them in your plan. Comfrey and horseradish grow well around a tree (just make sure to chop and drop them in place for the sake of the tree). Mints make an easy ground cover, as do clovers. The benefit of this method is reducing energy used to move biomass to the desired location.

Sources of Biomass

Trees produce massive amounts of biomass. Think about the leaves that fall in the autumn. A large oak or maple drops hundreds of pounds each year. Pruning to maintain your trees will provide you with even more in the form of logs and branches for your hugalcultures and limbs and leaves for chipping, should you have a chipper (a good investment, in my opinion). The drier your climate, the more important it is to break down limbs for mulching. In very humid climates, logs can break down fairly quickly, but in a climate like mine, it is worthwhile to break down sticks and branches to speed up decomposition.

Weeds are another source of biomass. Whatever grows of its own accord can be chopped down or, if desired, pulled up for soil development as you make space for more desirable plants. There is no need to get rid of all native or well-adapted species (weeds). In fact, their vigor can be used for the benefit of other species when you chop them down for biomass.

Nitrogen-fixers are excellent choices for biomass creation as they nourish the soil directly by nodules on the roots, and the biomass created above ground is also high in nitrogen. Alfalfa (lucerne) is a terrific choice for this, especially if you have open areas. Under good conditions, alfalfa can tolerate two or three mowings a season.

Mineral accumulators, such as comfrey and horseradish, also offer valuable biomass rich in minerals from deep within the soil. When these are mulched and incorporated into the top layer of soil, shallower roots can then access these minerals.

Perennial Herbs are terrific sources of biomass for mulching around plants for three reasons.

  1. They grow prolifically. This is especially true of sage, oregano, and any mint.
  2. They each have aromatic properties that repel some pests. I use the excess from these plants copiously in the shade where pests are more of a problem.
  3. These perennial herbs tend to thrive where other plants don’t. They can be a boon for those difficult places like along the sidewalk.

How to Use Biomass From Your Forest Garden

Once established, using biomass to enhance soil health is easy. Just go out with hedge sheers or preferably a hand sickle and cut down your biomass crops, usually to the ground. Also, prune anything that is crowding other desirable plants. You can leave them where they fall or move them to a plant that you want to encourage. Cutting the material into small pieces aids the decomposition. Burn or throw away any diseased plant material.

Timing is important but flexible. I try to allow biomass crops to bloom briefly to encourage pollinators, but after they have begun to bloom, I cut them down before they go to seed, unless I want to encourage propagation. Also, don’t cut biomass crops before they have a chance to become established. For plants such as jerusalem artichoke, which also produce a crop, you may want to wait until the crop is ready to harvest. However, I have grown huge crops of jerusalem artichokes even after chopping and dropping twice. In this case, I cut them to about three feet tall. Also, the biomass will decompose fastest in wet conditions, so if you have a wet season, this is an ideal time to chop and drop.

Nitrogen Fixing Biomass Crops

Biomass CropTypeNotes

Clover

Groundcover

Many varieties. Bee fodder.

Alfalfa

Herbaceous

Combines well with buckwheat.

Alder

Tree

 

Siberian Peashrub

Shrub or small tree

Edible pods, fodder

Autumn Olive

Shrub or small tree

Invasive. If you don't want the berries, you can harvest the biomass before fruit sets to prevent invasiveness.

Desert Indigo

Shrub

One of many valuable legumous shrubs.

This is one wheelbarrow load, pulverized with hedge shears and applied around the almond tree. It is a mixture of sage, comfrey, oregano, bindweed, and rhubarb.

This is one wheelbarrow load, pulverized with hedge shears and applied around the almond tree. It is a mixture of sage, comfrey, oregano, bindweed, and rhubarb.

I chop and drop this goldenrod whenever it encroaches on this red currant or other desirable plants.

I chop and drop this goldenrod whenever it encroaches on this red currant or other desirable plants.

Mineral Accumulating Biomass Crops

Biomass CropTypeNotes

Comfrey

Herbaceous

Once established (after growing season), comfrey can withstand up to 7 harvests a year.

Horseradish

Herbaceous

Cullinary uses. Can plant root from grocery store, but it may take a year before you see growth.

Perennial Herb Biomass Crops

Biomass CropTypeNotes

Sage

Woody/Herbaceous

Prune at the end of winter, before new leaves form. Prune after flowering, if desired. Prune to prevent crowding other plants. Grows quickly.

Mint Family

Herbaceous/ground cover

Wherever it becomes a nuisance, pull up to harvest biomass. Otherwise, chopping down works well. Many varieties. Most (other than oregano) tolerate shade.

Bee balm

Mint, see above.

Said to be mineral accumulator, bee fodder.

Peppermint

Mint, see above

Cullinary uses, repels some pests.

Lemon Balm

Mint, see above.

Salad vegetable, repels mosquitoes.

Oregano

Mint, see above.

Culinary uses. Repels some insects.

Adapting to Your Situation

Wherever you live, you can use biomass grown in your own garden for the fertility of your soil. I've listed species that grow well in a temperate climate, but the concept will work anywhere. Find what works where you are. Start with the pioneer plants that are already creating biomass on your property, if possible. Even the best garden soil will benefit from growing and mulching with biomass crops.