Ericaceous Compost

When planting acid-loving plants it is important to do so with the correct compost mixture. Ericaceous plants are species that love acidic soil and hate lime soils (acid lovers and lime haters). If you have found yourself drawn to a beautiful plant at the garden centre make sure you first find out which type of soil it likes, if you have chosen an acid-lover you should make sure to then buy some ericaceous compost too. 

This blog will cover everything you need to know about ericaceous compost, which plants need ericaceous compost, the effects and indications of an acid deficiency and, amongst other things, which compost to buy for your favourite ericaceous plants. 

What makes the compost ericaceous?

Ericaceous compost has a pH between 4 and 5.

When going DIY, this acidity can be cultivated from oak leaves, pine needles or coffee grounds. At a commercial scale unfortunately, peat is the main ingredient for acidity as it has a naturally low pH. Luckily many peat-free alternatives have been developed and are continually improving every year meaning your acid loving plants can have full rich blooms without costing the earth and damaging our native peat bogs. 

What does ericaceous mean?

Ericaceous is a word that refers to the family of plants that characterise this soil type- Ericas.

Ericas are heathers but the ericaceous plant group contains many more species than exclusively heathers. Heathers and other ericaceous plants are native to climates where soil conditions are acidic and largely infertile, generally with a pH between 4.4 and 6. Ericaceous acid loving plants are also referred to as calcifuges. This is a word derived from the Latin ‘to flee from chalk’ and of course contains all plants that are lime intolerant, growing only in acidic soils instead.  

Why use ericaceous compost?

Without the ericaceous soil the ericaceous plants may not establish and certainly will not flower. 

People often consider sunlight and water to be the full extent of planting conditions and overlook soil pH. Although this may seem like boring science to us, it is important stuff if you want the plants you love to grow happily (if you are a fan of ericaceous plants). For example if you wish to grow a colourful heather border you will need acidic soils achieved by the addition of ericaceous compost to your soil. Without the ericaceous soil the ericaceous plants may not establish and certainly will not flower. 

Which plants are ericaceous?

Here at Gardenwild we encounter ericaceous plants on a daily basis. The following species are some of our favourites and some we find in almost all the gardens we visit. They will look great in your garden too provided you read on to ensure you chose the right type of compost.  

1- Camellias

Camellia

Camellias are a very early flowering evergreen shrub that bears beautiful simple rosette shaped flowers on glossy leaves. Camellias are part of the theaceae family native to Japan, mainland China and south korea and need ericaceous soils. In a garden setting they can be used for early colour and evergreen structure.

2- Rhododendrons and azaleas

Rhododendron

Azaleas and Rhododendrons are both actually part of the same family but differ in their characteristics. Whilst rhododendrons are evergreen Azaleas shed their leaves in the winter, making them deciduous.  Their flowers are similar but differ in their floral blooms, Rhododendron flowers are generally bigger and bell shaped whilst the Azalea produces smaller more tubular funnel-shaped flowers. 

3- Ericas

Erica

These acid-loving flowering shrubs are, as previously mentioned, the origin of the term ericaceous. Ericas are heathers, the shrub native to the moors and peat-bogs of uplands of the UK but make great ornamental garden plants with their thick low-lying blossoms of rich colours. 

4- Blueberries and raspberries

Blueberry

Blueberries are a tasty and healthy sweet addition to your productive raised beds and are particularly demanding when it comes to soil pH in the garden. Similarly, raspberries can be a fun and delicious acid-loving berry although they are generally more tolerant to alkaline soils, however they will appreciate a feed of ericaceous compost. 

5- Roses

Rose

The star of the gardening world, roses too are a fan of acidic soils and need ericaceous compost. Adding ericaceous compost as well as organic matter will always improve the quality of your blooms. Roses ideally should be growing in soils between 6 and 6.5 pH. 

6- Asters

Aster

Symphyotrichum and asteraceae are acid-loving hardy perennials that love soils full of organic materials and a low pH. The flowers are colourful and daisy shaped that provide late colour towards the end of the summer.  

Will ericaceous compost turn hydrangeas blue? 

Simply, yes! Unlike almost all other plants the hydrangea flower can change its colour depending on the current soil pH. Hydrangeas growing in acidic soil will flower blue whilst alkaline soils will give pink hydrangea flowers. 

Hydrangea

You may have already heard of this amazing colour changing phenomenon in hydrangeas but how does it work? Pink flowered hydrangeas can change to blue easily with the addition of acidic materials such as iron salts or aluminium sulphate dissolved into water. This occurs because of the abundance of aluminium in the soil allowing for the blue flowers to bloom, a deficit of aluminium results in the formation of pink flowers. 

Despite the common belief amongst gardeners, it seems the rusty nail myth will result in a minimal pH change too negligible to change the colour of your hydrangeas flowers. If you don't feel up for a little garden chemistry experiment or a tetanus lucky dip in your beds, simply dig in ericaceous compost and top up with coffee grounds, oak leaves and pine needles if pH is still basic. 

Failing this, your best bet is a large bag of ericaceous compost, the following are our recommended selections:

Find out more gardening tip With our Beginners Guide to Gardening