How to Make Ericaceous Compost
A step by step guide to making compost for acid-loving plants
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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 closer to neutral.
If your soil isn’t naturally acidic, you’ll need to add Ericaceous compost several times 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.
I’ve seen first-hand what happens to such plants:
- Stunted growth
- Deformed stems
- Yellow colour
- Fewer flowers
What You’ll Need
I have experience in making ericaceous compost, as I had a large self-made hot compost bin at my previous property.
Below you’ll find my guide, follow these tips if you want to make your own compost.
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, you buy a plastic one online. I previously owned a hot composter, and they p[roduced compost in a fraction of the time.
Soil pH Testing Strips/Devices
I used to regularly test the compost pile to make sure the material was decomposing into compost with the required acidity. I found the cheapest way to do this was with pH testing strips.
Explore our list of preferred soil testing kits and off-site services here.
The Basics of Creating an Ericaceous Compost Pile
I’ve found the best place to locate the compost pile is on free-draining soil, or at least, a place where water doesn’t pool.
In my garden, I found a shady spot that was perfect, but somewhere in partial shade is also acceptable.
I suggest you start by placing twigs, leaves and other bulkier materials at the base of the pile in the composter.
Rather than just chucking everything in randomly, I always tried to create layers of “green” material and “brown” material.
“Green” items are:
- Fruits, including citrus.
- Grass cuttings.
- Green pine needles.
- Stems, flowers and other green garden items.
“Brown” items are:
When I created my own compost, I found my first attempt led to soggy, slimy compost, but by carefully layering the materials, I got perfect, usable material.
I suggest you 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.
Too many leaves, and it won’t degrade at all and will be too crunchy.
I always built the pile up to about 5 feet and kept the content moist but not waterlogged and never soggy.
I also got better results when I aerated the soil every week or so by turning it with a fork.
If you can put a lid or sheet over the top of the pile, I’m sure you’ll get better results as it keeps out rain and traps heat, which speeds up the composting process.
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.
- Green 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 into 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:
- Iron sulphate
- Aluminium sulphate
They also warn that excessive applications of aluminium sulphate can have adverse effects.
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.
Items You Shouldn’t Put in Your Ericaceous Compost Pile
I never put these in my ericaceous compost pile as they would lower the acidic content or compromise the content:
- Tap water as it’s slightly alkaline; I always used rainwater from my barrel instead as it’s naturally acidic.
- Hydrated lime, I’ve seen gardeners use this 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.
My Experience With Homemade Ericaceous Compost
I’ve previously tried to make my own compost for azaleas and a few other acid-loving plants I had growing at my previous property.
By regularly testing with pH strips I could see that the existing soil was gradually turning neutral so I tried to make my own compost to correct this.
The main issues I encountered were:
- The pile was too soggy (I didn’t layer it correctly, too many grass clippings).
- The composter didn’t do much in the winter (too cold, so I built a hot composter which was better).
- I also found the entire process very time-consuming for what was only a small amount of compost that I needed.
- I still had to buy additives for the compost.
- It was easier to just buy compost for my acid-loving plants.
If I had a huge area with dozens or even hundreds of acid-loving plants then it might have been worth my while creating my own ericaceous compost but for my few shrubs, the reward wasn’t worth the grind and I now buy the compost from a garden centre.
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. This is why I stopped making my own and now buy directly from garden centres.
What Type of Plants Require Ericaceous Soil?
There are thousands of plants that thrive in ericaceous soil, some of the more well-known and popular ones are: Bilberry, Heather, Gardenia, Trillium, Lily of the Valley, Rhododendron, Japanese Iris, Hydrangea and Begonia.
Pine trees thrive in acidic soil, and if you want to grow plants under pine trees, you’ll need to choose ones that prefer slightly acidic soil. I’ve previously tried to grow regular plants under pine trees, and they never reached their true potential.
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.
What is the Best Composter?
You can create ericaceous compost in any garden composter. We recently reviewed the HotBin compost bin in our guide to the best hot composters, go check it out.
Meet The Author: Hannah Miller
Hannah is a former NHS administrator, mother of two and keen gardener with a horticulture qualification who loves growing new plants and experimenting in the garden.
She enjoys gardening as much as she cares about the environment and likes to share her knowledge with others.
This year is all about pollinators, and Hannah has set herself the goal of only buying new plants that attract pollinators; she aims to make the garden as bee and butterfly friendly as possible.
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