Living Mulch

Healthy soil is the basis for beautiful, bountiful gardens. To sustain, protect and build this precious resource, mulch is often used. While familiar organic mulches such as straw or wood chips are often used, some gardeners incorporate a living mulch into their garden space. Cathy Christie re-imagines our vegetable plot in this week’s Ask a Master Gardener.

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Soil is Alive

In 2020, the United Nations Food and Agriculture Organization published “Soil is Alive”, which describes the incredible amount and diversity of life beneath our feet. According to this source:

  • Twenty five percent of the planet’s biodiversity lives in our soils
  • There are more organisms in one gram of healthy soil than there are people on earth
  • Each year, 75 billion tons of soils and their organisms are stripped from the land by wind and water erosion
Image credit: Food and Agriculture Organization of the United Nations

This species richness, so important for healthy soil, supports plant growth. According to the UN FAO, implementation of sustainable soil management, could result in production of 58% more food to support our planet’s human population. 

What is Living Mulch?

Sustainable management practices maintain and build soil health.  One such practice is the use of mulch, with benefits including:

  • Reduced erosion 
  • Fewer weeds
  • Increased water retention
  • Improved soil structure
  • Regulation of soil temperature
  • Habitat for beneficial insects

A living mulch can be achieved by simply interplanting or under sowing a crop with low growing annuals or perennials that will cover the soil. For example, plant sweet alyssum with its shallow roots, among Swiss chard, which has a deeper root system.  Consider calendula, marigolds or nasturtium in between lettuce plants.  

Some living mulches can act as a ground cover where foot traffic is expected – wooly thyme for example handles this well.  Others, such as legumes, add nitrogen back to the soil.

At the end of the growing season, simply “chop and drop” your living mulch, leaving the plants to decompose, returning the nutrients they took up back to the soil.

A New Tradition?

A traditional vegetable garden is usually planted in orderly rows; a bed of tomatoes, another with leafy vegetables and a third with peas or beans.  Flower beds are located elsewhere, perhaps at the front of the house. 

In industrial scale farming, rows make sense – after all, harvesting is mechanized and the goal is cost effectiveness.  But in her home garden, Cathy wonders why flowers and vegetables should be planted separately and suggests order is over-rated!  In her garden she imagines a wandering path with stepping stones through a mingled mixture of vegetables and flowers. A living mulch adds benefits and beauty to her space.

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