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How to Make Ericaceous Compost

A step by step guide to making compost for acid-loving plants

Compost Making – Made Easy

Created by the team at DIY Gardening

If you’re new to gardening, you may find it difficult to choose the best compost for your plants. Each plant, whether it’s a bush, an ornamental plant or a vegetable, will thrive in a specific type of soil.

One way of measuring the content of the soil or compost is to test its pH level (see how to test soil here).

pH is a measure of the soil’s acidity and alkaline levels. 7 is neutral while any number below this indicates more acidic soil while above 7 indicates more alkaline in the soil.

Choosing the right plants for your soil or changing your soil’s pH is a crucial step if you want your plants to thrive.

Blueberries and Heathers, for example, thrive in acidic soil with a pH of between 4.5 – 5 while Lavender prefers alkaline soil between 7 and 7.5.

What is Ericaceous Compost?

The Ericaceae is a family of over 4000 plants that are commonly found in either acidic or infertile conditions.

Ericaceous compost is organic matter with a pH level well below 7. Most Ericaceous composts sold in garden centres contain organic matter with a reading of around pH 5.

You can buy Ericaceous compost from most garden centres but as compost gradually breaks down into the soil, the pH gradually increases until it’s neutral.

If your soil isn’t naturally acidic, you’ll need to add Ericaceous compost each year to maintain a pH level well below 7.

What Happens if You Plant Acidic-Loving Plants in Alkaline Soil?

If your plants require acidic soil -7 and you plant them in alkaline soil 7+, the plants will not be able to absorb enough iron and other key nutrients.

You can expect the plants to then turn a sickly yellow colour, they may not flower fully, root growth will be stunted and the stems deformed. 

What You’ll Need 

A Compost Heap or Bin

You can make your own compost bin from old wooden pallets, it’s easy and takes less than half an hour and is the most eco-friendly option.

Alternatively, buy a plastic one online or, if space is limited in your garden, buy a tumbler.

Soil pH Testing Strips/Devices

You’ll need to regularly test your pile to make sure the material is decomposing into compost with the required acidity.

Explore our list of preferred soil testing kits and off-site services here.

The Basics of Creating an Ericaceous Compost Pile

You should locate the compost pile on soil that’s free-draining, or at least, a place where water doesn’t pool.

A shady spot is best, but partial shade is acceptable.

Start by placing twigs, leaves and other bulkier material at the base of the pile.

As you add material to the pile, try to create layers of “green” material and “brown” material.

“Green” items are:

  • Fruits including citrus.
  • Vegetables.
  • Grass cuttings.
  • Stems, flowers and other green garden items.

“Brown” items are:

  • Leaves.
  • Twigs.
  • Straw.
  • Sawdust.
  • Cardboard.
  • Paper.

Don’t let any one item dominate the pile as it will disrupt the composting process. For example, too thick a layer of grass cuttings and you’ll get slimy sludge instead of soft fluffy compost.

Build the pile up to about 5 feet and keep the content moist but not waterlogged and soggy.

You’ll need to aerate the material by turning it occasionally with a fork. 

In general, compost heaps perform best when they have a lid or cover to keep out excess rainwater, when some warmth is retained, excess moisture is allowed to drain out, and the material is well-aerated. 

How to Make Ericaceous Compost

To ensure your compost is ericaceous and suitable for acid-loving plants, you’ll need to add some of the following items:

  • Leaves – most have high acidic content, esp leaves from Beech and Oak.
  • Pine needles, these also have high acidic content.
  • Coffee grounds and used tea bags as most are now plastic-free.
  • Citrus fruits, including the peels, just chop them int0 smaller pieces so they decompose more easily.
  • Onions, finely chopped, not whole.
  • Sawdust from freshly cut wood.
  • Fine bark or wood chips, for example, from a shredder.

The Royal Horticultural Society Recommends:

To acidify soil for acid-loving plants, the RHS recommends adding the following:

  • Sulphur
  • Iron sulphate
  • Aluminium sulphate 

They also warn that excessive applications aluminium sulphate can have adverse effects. 

The full article from the RHS can be found here.

Sulphur Pellets

These sulphur pellets help to acidify the soil and last up to two years.

Add them to the compost as you use it in the garden or in containers.

Iron of Sulphate

These granules should be applied every 6-8 weeks and are perfect for pots, borders and veg patches.

You can find iron of sulphate in most garden centres, it can also be used on lawns where it turns the grass bright green.

Items You Shouldn’t Put in Your Ericaceous Compost Pile

Don’t put these in your ericaceous compost pile as they lower the acidic content or compromise the content:

  • Tap water as it’s slightly alkaline, use rainwater instead.
  • Hydrated lime, this is often used to speed up the process but it has a high alkaline content.
  • Items that are rich in calcium which is alkaline.
  • Meat, human or pet faeces, bones, glossy paper, plastics, glues etc.

FAQs For How to Make Ericaceous Compost

What is the Best pH Level for Soil?

Different plants all require different pH levels so you’ll need to research each plant you intend to use in your garden. Most plants, including grasses, will thrive in soil that has a pH score of between 6 and 7 – sightly acidic. Some plants, however, prefer more acidic or slightly more alkaline soil.

Does Ericaceous Compost Stay Acidic Forever?

Ericaceous compost will breakdown and decay into a neutral soil over time so you’ll need to top up your soil with fresh ericaceous compost and/or additives such as sulphur and iron of sulphate.

What Type of Plants Require Ericaceous Soil?

There are thousands of plants that thrive in ericaceous, some of the more well-known and popular ones are: Bilberry, Heather, Gardenia, Trillium, Lily of the Valley, Rhododendron, Japanese Iris, Hydrangea and Begonia.

What Happens if I Grow Ericaceous Plants in Soil That's Too Alkaline?

The plant won’t be able to absorb enough iron and other key nutrients, this will result in the plant not flowering, turning yellow and possibly dying.

Can I use Peat to Make Ericaceous Soil?

Peat moss is acidic so is a popular additive to compost and soils, unfortunately, it’s also very bad for the environment as the mining process destroys animal habitats and releases harmful gases into the atmosphere.

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This guide to making ericaceous compost was created by the team here at DIY Gardening

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