Do Lilacs Need Ericaceous Compost?

Do Lilacs Need Ericaceous Compost

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Lilacs are a gorgeous addition to any garden. With their plentiful bunches of flowers, sweet aromas, and ability to attract pollinators like bees and butterflies, it’s no wonder you want one or several! The only questions are, what soil should you plant them in, and does ericaceous compost work?

Lilacs don’t need ericaceous compost to survive and thrive. Lilacs prefer between 6.5 and 7.0 on the pH scale, and ericaceous compost can make the soil too acidic. However, compost is useful if lilacs are in too alkaline soil, though commercial fertilizers can work better.

Lilacs are not finicky shrubs to grow, but it is important to know what it wants to get the best results. Keep reading to find out exactly how ericaceous compost would affect Lilacs and the type of soil they prefer.

Do Lilacs Grow in Ericaceous Compost?

To answer this question, we should find out what soil conditions lilacs favor the most. Lilacs are flowering shrubs that aren’t especially picky with the dirt they’re planted in. Nevertheless, they do have their favorite.

Lilacs love soil that is:

  • Loamy
  • Well-drained
  • Nutrient-rich
  • Humus-rich

Loamy soil is soft and crumbly and is composed of equal measures of sand, silt, and clay. It’s wonderfully aerated while also compressing and retaining some water. Since lilacs don’t like their roots flooded, the addition of larger particles (i.e. sand) to improve drainage is good. 

Finally, all plants love having the nutrients they need, but like lilacs, they prefer the nutrients to be “finished.” That’s when compost can’t decompose anymore and is as rich as it can be.

This makes all of the nutrients available at once, but the particles are very small, so you have to be careful not to overwater. 

Does ericaceous compost satisfy a lilac’s wants? It can be nice and loamy with its pine needles, wood chips, and coffee grounds, but it’s better to supplement the soil that is already loamy and well-draining because it doesn’t change the existing consistency.

What pH Level do Lilacs Like?

Lilacs are flowering shrubs that prefer neutral, slightly alkaline, or slightly acidic soil. Soil pH is measured on a scale from 0-14. If you use a pH strip to test your soil, 0-6 is considered acidic, 7 is perfectly neutral, and 8-14 is alkaline.

Lilacs can thrive in soil that is slightly acidic, neutral, or slightly alkaline, but the numbers they seem to love the best on the pH scale are 6.5-7.0.

If you have alkaline soil, the most alkaline we would say you can get away with is an 8.0. If the soil is too alkaline, it severely affects the structure of the soil and especially nutrient availability. It’s the same problem with soil that’s too acidic, too.

While you’re checking the pH level, make sure the soil has the qualities we recommended in the previous section:

  • Nutrient-rich
  • Well-draining
  • Humus-rich

If you’re sure your soil has these qualities, but something isn’t right, check to make sure your soil is properly preparedOpens in a new tab. with enough time before you start planting.

Does Ericaceous Compost Benefit Lilacs?

The purpose of ericaceous compost is to make soil that it’s added to richer in nutrients. It’s often suitably used for flowering plants, shrubs, trees, and succulents that may be lacking those nutrients. It’s also commonly used to raise the acidity (lower the pH) of the soil. 

If your soil is way too alkaline, ericaceous compost is a good mixture to combine with your existing soil. It can improve the acidity of the ground enough to help neutralize the pH.

It will also make the nutrients that can’t break down in alkaline soil more soluble so that the lilac bush can get the nutrients it may have been lacking. 

Alkaline soils make a few important minerals available to plants, such as

  • Magnesium sulfate
  • Calcium carbonate
  • Sodium
  • Phosphorous

However, other essential minerals for lilacs that alkaline soil doesn’t dissolve include:

  • Nitrogen
  • Hydrogen
  • Aluminum
  • Sulfur

Will Ericaceous Compost Hurt Lilacs?

You must have heard at least once in your life, “too much of a good thing is a bad thing.” It’s the same for your lilacs and amending the soil to be more acidic. 

If the compost turns the soil from Alkaline to neutral, it will be okay. The only problem you could face would be if, by adding more ericaceous compost, you take the pH of the soil too far beneath the recommended pH level of 6.5. 

Ericaceous compose usually has a pH of 4 or 5Opens in a new tab., which is very acidic. You want to be careful about adding too much acidity because it can inhibit your lilacs from absorbing waterOpens in a new tab. properly.

Whether it’s too acidic or too alkaline, the same kind of problem happens: the lilacs can’t absorb the nutrients it needs. Lilacs require three nutrients in particular:

  • Phosphorous
  • Potassium
  • Nitrogen

Both Phosphorous and potassium are used to promote root health as well as spur flower production in lilacs. They also assist lilac immunity against diseases and pests.

Potassium will increase the pH in soil, but it can come in two forms. Potassium sulfate has potassium and sulfur, and sulfur can make the soil more acidic. A potassium hydroxide solution, otherwise known as pH Up Concentrate, can be found as a 50% solution in stores.

Meanwhile, nitrogen – which also lowers pH – promotes lush green foliage. This video has more information on what you need to know about lilacs. 

How Much Ericaceous Compost Do I Need?

Taking what we’ve learned so far, we know we don’t want to mix too much compost with your lilac’s current soil. Compost, especially ericaceous compost, is usually very low in phosphorus and potassium while high in nitrogen.  

In other words, while your lilac will have thick foliage, it won’t bloom, may develop poor root health, and may make your shrub vulnerable to getting sick or eaten.

If you use ericaceous compost to make the soil richer in nutrients and help the lilac absorb the food it wouldn’t have otherwise had in the alkaline dirt, you need to amend those two deficiencies. 

If your soil already has a slightly high pH, containers with ⅓ of their volume with compost will sufficiently neutralize the mixture.

If your lilacs are in beds of their own rather than a container, we would recommend putting a 2-4” layer of the compost on top and then thoroughly mixing it in. That last step isn’t necessary if you have worms.

If your soil was neutral, to begin with, and the ericaceous compost turns it a little too acidic, you can add things like

  • Wood ash
  • Kelp meal
  • Bananas & banana peels

To increase the potassium and raise the pH a little. Phosphorus can be found in 

  • Manure
  • Bone meal
  • Fish meal

Can Lilacs Get What They Need with Other Compost Mixes?

What’s important to remember about fertilizing your lilac shrubs is that lilacs absolutely LOVE soil that’s been enriched with organic matter, making compost a generally good idea. However, you don’t necessarily need ericaceous compost to fertilize your lilacs. 

There are viable commercial fertilizers that will work for these resplendent shrubs, namely any fertilizer mix with a nitrogen, phosphorus, and potassium mixture (N-P-K) of 10-10-10. 

That will give them the nitrogen they need to flourish and the potassium and phosphorus they need to stay strong and create a multitude of flowers. Other minerals help lilacs grow, like calcium, but so long as you have the big three for a flowering shrub, that’s the most important thing.


So you can grow lilacs in ericaceous compost, but they don’t usually need ericaceous compost. The compost would only be great to use if the lilacs suffer from a mix that is too alkaline.

Even after adding the compost, you’ll need to watch it to ensure there isn’t stunted growth, indicating a phosphorus or potassium deficiency.


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