Understanding Ericaceous Compost: All You Need to Know About Acid-Loving Plants and Soil

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Understanding Ericaceous Compost: All You Need to Know About Acid-Loving Plants and Soil

The term “Ericaceous” refers to a family of plants in the Ericaceae family—heathers and other plants that grow primarily in infertile or acidic conditions. But what is ericaceous compost? Read on to learn more.

Ericaceous Compost Info

What is ericaceous compost? In simple terms, compost is suitable for growing acid-loving plants. Plants for acidic compost (ericaceous plants) include:

  • Rhododendron
  • Camellia
  • Cranberry
  • Blueberry
  • Azalea
  • Gardenia
  • Pieris
  • Hydrangea
  • Viburnum
  • Magnolia
  • Bleeding heart
  • Holly
  • Lupine
  • Juniper
  • Pachysandra
  • Fern
  • Aster
  • Japanese maple

How to Make Compost Acidic

While there’s no ‘one size fits all’ ericaceous compost recipe, as it depends on the current pH of each individual pile, making compost for acid-loving plants is much like making regular compost. However, no lime is added. (Lime serves the opposite purpose; it improves soil alkalinity—not acidity). Begin your compost pile with a 6 to 8 inch (15-20 cm.) layer of organic matter. To boost the acid content of your compost, use high-acid organic matter such as oak leaves, pine needles, or coffee grounds. Although compost eventually reverts to a neutral pH, pine needles help acidify the soil until they decompose. Measure the surface area of the compost pile, then sprinkle dry garden fertilizer over the pile at a rate of about 1 cup (237 ml.) per square foot (929 cm.). Use a fertilizer formulated for acid-loving plants. Spread a 1 to 2-inch (2.5-5 cm.) layer of garden soil over the compost pile so the microorganisms in the soil can boost the decomposition process. You can use finished compost if you don’t have enough available garden soil. Continue to alternate layers, watering after each layer until your compost pile reaches a height of about 5 feet (1.5 m.).

Making Ericaceous Potting Mix

To make a simple potting mix for ericaceous plants, begin with a base of half-peat moss. Mix in 20 percent perlite, 10 percent compost, 10 percent garden soil, and 10 percent sand. If you are concerned about the environmental impacts of using peat moss in your garden, you can use a peat substitute such as coir. Unfortunately, there is no suitable substitute for peat when it comes to substances with a high acid content.

Dr Heidi Parkes

By Dr Heidi Parkes

Senior Information Extension Officer QLD Dept of Agriculture & Fisheries.