What is Ericaceous Compost: how do I use it?

Ericaceous compost will be your strongest ally when growing acid-loving plants. Gardeners usually struggle to grow these types of plants because if the soil pH is too high, they simply won’t grow or will become extremely weak. . By the end of this article, you’ll know lots about ericaceous compost – why it’s important, how to make it, and how to use it.

Ericaceous compost is acidic compost that can be applied to ericaceous plants. You can buy it from garden centers or make your own to supplement your soil or fill containers

What is ericaceous compost?

Ericaceous compost is just a fancy term for acidic compost with a low pH. Ericaceous compost is designed to be acidic specifically for plants in the Ericaceae plant family. 

Acidic compost is virtually the same as regular compost, only that acidic materials such as pine needles and oak leaves are introduced to lower the pH. To make your own ericaceous compost, check out our explanation below.

Why would I need ericaceous compost?

At this point you might be wondering, why would I need ericaceous compost? What happens if acidic plants find themself in neutral or alkaline soil? 

If ericaceous plants and lime-hating plants are grown in neutral to alkaline soils their growth will be stunted and they might develop chlorosis. Chlorosis is when the plant isn’t able to uptake enough nutrients in the soil.

Pink azaleas bush in a garden
Azaleas love low pH soil and ericaceous compost

For acid-loving plants, this doesn’t mean that the nutrients aren’t there. It means that the plants simply can’t take advantage of them because the soil pH is too high. Ericaceous compost helps you prevent chlorosis by maintaining the soil pH acidic.

Which plants should I use ericaceous compost on?

You can use ericaceous compost on ericaceous plants. As you can probably guess, ericaceous plants are those who enjoy acidic conditions and are lime-hating. Naturally, they can also be called be called ‘acid-loving plants’ or ‘lime-hating plants’.

The most common acid-loving plants are blueberries, azaleas, hydrangeas, rhododendrons, camellias, and callunas. These plants are ideal for growing together because of their preference for acidic soils. If these ericaceous plants aren’t grown in soils with an acidic pH, their leaves will turn yellow, they will grow slowly, won’t flower, and will be very weak. 

Acid-loving plants don’t do well in alkaline soils because they need lots of iron to sustain growth. In neutral and alkaline soils, iron stays insoluble and isn’t available to the plants. Depending on your soil type, you’ll use the ericaceous compost to modify neutral soil or fill containers. But I’ll go more into that in the next section.

There are also some plant varieties that do great in all sorts of soils. However, they do best grown in acidic soils because they will be less vulnerable to diseases. Potatoes are a great example of this since they won’t develop a disease called scab. Other examples of plants that do best in slightly acidic soil include tomatoes, peppers, and beans.

How to use ericaceous compost?

You can use ericaceous compost to slowly modify neutral soil pH, replenish acidic soil, or fill containers for ericaceous plants. Depending on your situation, choose the strategy that works best for you, your soil type, and growing conditions. Do a soil ph test to check what your soil is at first.

blueberry bush
Blueberries thrive in low pH soil

If your soil has a neutral pH, you can slowly push it towards a slightly more acidic pH by incorporating lots of ericaceous compost. It won’t happen overnight, but with time and concentrated efforts, you can be successful. If your soil is already alkaline, ericaceous compost won’t have a big enough impact.

Should your soil already be acidic, you’re in a perfect position to grow ericaceous plants. Just don’t forget that acid-loving plants also need routine applications of compost to feed the microbes and restore soil nutrients. Applying ericaceous compost will ensure that you maintain the acidic pH and are introducing microbiotic life already adapted to an acidic environment.

If your soil is alkaline, you’ll want to grow your ericaceous plants in containers. Trying to amend the soil for them in one season is not very effective so it’s best to fill containers with acidic soil. My favorite way to make a soil mix for lime-hating plants is to combine equal parts of regular potting soil with ericaceous compost.

Watering ericaceous plants?

Most ericaceous plants are shallow-rooted and don’t tolerate dry periods. This means that rain must usually be supplemented with hand watering, especially in the summer.  If hand-watering your acid-loving plants, special attention must be paid attention to the water quality.

Municipal water tends to be treated with additives and has an alkaline pH.  Infrequent watering with hard tap water won’t be a big deal in the short run. However, if your garden relies primarily on hard water for humidity, then make sure to do a pH test. Over time, the alkaline pH of the water will affect your plants.

If watered often with hard water that contains lime, the leaves of your ericaceous plants will turn yellow and begin to weaken. If this is your situation, try harvesting rainwater or neutralizing your water with a diluted liquid fertilizer for ericaceous plants.

Fertilizer for ericaceous plants?

You can pick up fertilizer for your ericaceous plants at your local garden center or you can just apply ericaceous compost. Compost acts as fertilizer as the bacteria in the soil break down the organic matter and release the nutrients. You can learn more about how compost works as fertilizer in our article on soil microbes.

If you choose to apply actual fertilizer, choose one that is specifically designed for acid-loving plants. A slow-release fertilizer works best for perennials which will stay in the ground for many years. On the other hand, a fast-acting liquid fertilizer can be super useful for adjusting the water pH if you need to use tap water in your garden.

How could I make ericaceous compost at home?

To make your own at home follow the same principles as you would for conventional compost. The only difference is that you should make a point to add acidic materials.

blue hydrangea  in acid ericaceous compost
Hydrangeas will produce blue flowers in acid soils and ericaceous compost and produce pink flowers in alkaline soils.

You can add prunings from your ericaceous plants as well as pine needles, oak leaves, and the rinds of your citrus fruit. Others suggest adding coffee grounds, but they aren’t all that acidic so it won’t contribute much other than organic matter (which is also great!).

To go the extra mile or if you can’t source pine needles or oak leaves, add a little bit of garden-grade sulfur to your compost pile. This one ingredient will singlehandedly lower your pH, but you must be extremely careful when measuring out the amounts. Too much sulfur will shift the balance to be far too acidic.

Conclusion

If you’re looking to grow acid-loving plants, ericaceous compost will be your best friend. It will modify the soil pH to be more acidic, act as fertilizer, and prevent chlorosis.

By making your own ericaceous compost, you can have an almost limitless supply of compost specifically designed for your acid-loving plants. Specialized compost like this tends to be much more expensive from gardening centers (in comparison to normal compost).