General gardening topics

When to use ericaceous compost on Hydrangeas

Last updated on April 7th, 2022

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Hydrangeas are a pretty flexible shrub in that they will tolerate most soils, as long as it is well-draining and rich in nutrients. But there are times when ericaceous soil is best. 

But what is it?

Ericaceous Compost

Ericaceous compost is a type of acidic compost that is lime-free. It is not suitable for all plants, only those which prefer highly acidic soil such as Hydrangeas, Pieris, Rhododendrons and Azaleas. You can also find ericaceous compost that functions the same and is meant for plants that can only tolerate acidic conditions and you want to grow them in pots and containers or add a little boost when planting them in the ground. 

Hydrangeas and Ericaceous Mixes

Hydrangeas can be acid-loving plants and this means they can thrive in acidic conditions and do well in acidic soil. If you already have them in acidic soil, then you can help their nutrient content by adding ericaceous compost the same as you would mix compost in with your soil in all other situations. This can be at the start of spring as the plants are growing the most, or when you prepare a pot ready for a Hydrangea to be planted. If you have lighter soil, then ericaceous compost can prove most beneficial. 

Scotts Miracle-Gro Levington Ericaceous Compost 50 Litres
  • NPK 3.2-3.4-3.6
  • For use with seed trays, houseplants, hanging baskets and containers Precisely balanced to allow germination of seeds, yet strong enough for vigorously growing plants
  • Makes 100 litres of compost
  • Contains trace elements and wetting agent

You can change the colour of a Hydrangea’s flowers

How to change the colour of hydrangeas - Changing the bloom colours from pink to blue or blue to pink is based on the soil pH. The pH level of the soil will only change the colour of the mop head or lacecap hydrangeas.

Big Leaf Hydrangeas, the most common variety with pink and blue flowers, are of particular interest here because you can control the colour of the flowers by making the soil highly acidic. If you have pink or purple flowers and you want blue ones, it is time to add some ericaceous compost. 

If you want to change the colour of your blooms and you are certain you have a Big Leaf variety, you can change the soil and compost to one that is more ericaceous and watch as the colours change from one season to the next.

Learn more about changing the colour of the flowers on your Hydrangea in this guide

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Before you do this it is recommended that you invest in an at-home pH test kit. These soil test kits are relatively inexpensive and are very easy to use. You can test the soil in multiple areas of your garden where you plan to grow Hydrangeas to see what the current pH level is. With the results, you can determine whether your conditions are highly acidic, meaning they would need very little alterations to the compost if any, or if they are highly alkaline in which case they would need a lot of ericaceous compost, and ericaceous fertiliser.

You can invest in multiple kits and use them on a regular basis because getting this type of change won’t happen instantly so you’ll want to test the soil regularly as you integrate ericaceous compost or soil so that you can see how good the results are, and make any further amendments or stop adding the compost, depending on your needs.

With this, it is important to note that if your soil is heavily alkaline and you use ericaceous compost to change the acidity, you will need to do that every year to keep the colour of the flower you have because the soil will naturally revert back to its original condition.

Vitax Hydrangea Colourant Enthusiast Range,250g
  • Pale pink varieties tend to blue best
  • Darker pink varieties turn to mauve/blue
  • Treat as per pack instructions

Related articles you may be interested in

Pests and diseases that affect Hydrangeas

The best Hydrangeas for planting in a shady spot

Are your Hydrangea leaves wilting and turning brown?

How to prune Hydrangeas correctly to avoid non-flowering

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Last update on 2024-07-05 / Affiliate links / Images from Amazon Product Advertising API

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