Since it’s winter, we sometimes light our wood-burning fireplace, but we weren’t sure how to reuse the wood ashes. So, I wondered if our citrus trees would like them as a fertilizer. I did some research to find out if this was a good idea. Here’s what I found.

Citrus trees prefer a soil pH of 6.0-7.0, and since wood ash is extremely alkaline at 9.0-11.0, it’s not ideal to use it as a fertilizer. However, if you find that your citrus tree’s soil is too acidic (below 5.5), then adding some wood ash to raise the pH and make it more alkaline can help.

In this article, we will explore everything you need to know about wood ash and citrus trees, including tips to amend citrus tree soil and caring for the trees. Let’s jump in.

Is Wood Ash Good for Citrus Trees?

wood ash in a fireplace

Wood ash is not a great fertilizer for citrus trees due to its high alkalinity. Better options for citrus trees include more acidic amendments such as sand, coffee grounds, or peat moss. When in doubt, consider testing your soil’s pH and adjust it if needed.

By adding wood ash, your citrus tree’s soil will become much less acidic. However, wood ash also provides calcium, which is good for the tree’s root development.

The minerals that can be found in wood ash include calcium, potassium, phosphorus, manganese, and magnesium.

All these nutrients are great for citrus trees, but a nutrient imbalance can pose a problem. Check that your citrus trees do not have more nutrients than it needs, especially if you’re using wood ash with other fertilizers.

A good fertilizer to get for your citrus tree is one with an NPK (nitrogen, phosphorus, and potassium) ratio of 2:1:1. For more information, and to see which citrus fertilizers I recommend, you can check out my recommended citrus fertilizer page.

Why Wood Ash Isn’t Good for Citrus Trees

Citrus trees cannot grow when their soil is too alkaline because the high pH blocks the nutrient uptake of the citrus trees. So, using wood ash as a primary fertilizer for your citrus trees isn’t ideal. Wood ash should only be used when the pH of the soil is too acidic (below 5.5) and stopped when the pH reaches 6.0.

Wood ash has a pH of 9.0-11.0, and this high alkalinity blocks the uptake of nutrients for the plant. Overall, it’s okay to use wood ash for citrus trees in small amounts. When dissolved in water, wood ash is nearly pure alkaline, which doesn’t work for the 6.0-7.0 pH that citrus trees need. 

So, what soil amendments should you use instead of wood ash?

What To Use Instead of Wood Ash

Considering citrus fruit are acidic themselves, they naturally need slightly acidic soil. So, let’s look at some acidic fertilizers and amendments.

Instead of wood ash, you can use acidic citrus fertilizers or amendments such as sand, peat moss, and coffee grounds.

Compost is also great for citrus trees but can be slightly alkaline, so use it in small amounts. I recently had a vermicompost bin and applied some worm castings to the top of the soil for my potted Meyer lemon tree. In just a week or so, the growth has been dramatic! New growth is shooting up out of nowhere, and tons of buds are emerging.

However, if you’re like me and still want a place to use your wood ash, there are some alkaline-loving plants you can check out.

More Tips To Improve Citrus Tree Soil

If you’d like to further improve your citrus tree soil, check out these tips I’ve come across in my research (and testing) and consider implementing some of them.

  • If you live in a hot and sunny climate (if you have citrus, chances are you do), you can protect the soil from baking in the sun by providing a 1-2 inch layer of mulch. Some mulches you can use are leaves, grass clippings, or bark. This will also keep the moisture in, so you can water your citrus trees less.
  • Use a high-quality, organic citrus fertilizer at the start of every growing season. This will help you citrus trees produce the maximum amount of fruit each season.
  • If you have a potted citrus tree, consider changing the pot’s soil every 3-5 years. When repotting, you also might need to either increase the size of the pot or prune the tree’s roots as it grows.
  • Make sure the soil is well-draining. If you have a planted citrus tree that needs soil with more drainage, consider elevating the tree by planting it on a hill or a garden bed. For potted trees, you can drill more holes in the bottom of the pot (and repot the soil if it’s collapsed).
  • Measuring the pH is most commonly done with either pH strips or a pH meter (I suggest the meter as it can be quicker to use). To see the pH meter, along with a list of other tools I recommended, you can check out my tools page.

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