When I was first helping my parents with their backyard garden in Ventura, California, breaking the clay ground proved to be incredibly difficult. However, they had lemon, lime, orange, and tangerine trees, so something in the soil had to be working for them. I wanted to learn more so we can start planting even more citrus trees. So, can citrus trees grow in clay soil and how can you amend the soil?
Citrus trees can successfully grow in clay soil, but they grow better in sandy or loamy soils. While clay soil won’t kill already established citrus trees, it can make it harder for young citrus trees to grow. The best way to grow citrus in clay soil is by first amending it with sand or compost.
So, while there are some effective ways you can amend your clay soil, what is so bad about clay soil in the first place? What does it do to citrus trees? Let’s take a further look.
Why Is Clay Soil Bad for Citrus Trees?
Clay soil isn’t a good growing medium for citrus trees due to the high density and pH of the soil. Most clay soils are compact which holds water and prevents roots and worms from burrowing. Clay is also alkaline, with a pH that’s too high for citrus trees. This can block nutrients from being absorbed by the tree.
If you have clay soil, it’s super important for worms and roots to break into the ground and spread nutrients throughout the soil. This will revive the beneficial bacteria in the soil and provide a great growing medium for just about every plant in your garden. It will also balance the pH, provide oxygen to the roots, and improve drainage.
To recap, here’s a list of why clay is bad for citrus trees:
- Poor drainage
- Creates water runoff on the surface
- pH is too high
- Lacks nutrients
- Blocks roots and worms from digging
So, if clay soil isn’t great for citrus trees, then what type of soil is?
What Type of Soil Is Best for Citrus Trees?
The best kind of soil for citrus trees is a rich, well-draining, loamy soil that has a pH of 5.5-6.5. The soil should also be loose, but still clump up slightly when wet. A loamy soil that has sand mixed in is even better as sand provides better drainage and a slightly acidic pH.
Clay soils are often dry and form hard clumps, even when wet. By having sandy, loamy soil, the citrus tree will have enough space and water retention to grow strong roots.
The slight acidity of the soil will also help the tree absorb more nutrients, which will help the tree grow faster and healthier. Healthy citrus trees can fend off more pests and diseases than weaker ones.
But how do you turn your clay soil into one that’s loamy and supports citrus trees’ needs?
How to Amend Clay Soil
Before amending your clay soil, you should test it for drainage by digging a hole 1 foot wide and 1 foot deep and filling it with water. If after 6 hours the water is still not drained, you should definitely look at adding organic material and amending the soil. So, how exactly do you amend clay soil?
You can amend clay soil by mixing in sand or compost. Sand and compost both help balance the clay by providing a more balanced pH and adding larger particles to break up the clay. Additionally, you can use cover crops to break into the ground and start building nutrients into it.
There are many other ways to amend clay soil, but I’m going to cover three of the easiest and most effective methods.
- Add sand
- Add compost
- Build worm “towers”
Let’s jump in and see which of these soil amendments you’d be most interested in.
The first way you can amend your clay soil is with sand. Simply put, the smaller particles of clay is what helps it stick together. If you mix in sand, the larger particles will prevent most of the clumping from occurring. This helps the drainage and aeration of your citrus tree’s roots. The downside to this is if you’re trying to amend a lot of soil, you’ll need a lot of sand. A good ratio is 1:1, equal parts sand to the clay soil.
The second way is with compost. Using compost can be easier than sand as you can generate a lot of it yourself. You can also mix in leaves, grass clippings, and branches to break up the clay soil. These materials will compost over time and attract earthworms to further work the clay soil. Similar to sand, a 1:1 ratio is best to work into the ground.
Worm Towers (“Connect the Dots”)
The last way is perhaps the easiest as you will be letting nature do most of the work. The method I’m referring to is building worm “towers” into the ground. If you make just a few, the worms will close the distance between them and work the clay into rich soil for you.
To start, take your planting area for your citrus trees and find its four corners. Next, choose a corner and dig a narrow hole 2-3 feet deep (the deeper the better). Fill it with organic material such as leaves, grass, and food scraps. Place red wriggler worms, or some worms from your garden, on top. Anywhere from 20-50 worms would be a good start. Cover the worms with a few inches of dirt or leaves.
Repeat this 2-4 more times, spacing out these towers by about 5 feet. The worms will feed off of the material you’ve provided and will spread it throughout the soil. It won’t take them long before they start searching for more food, and some will find the other towers. It’s like they’re playing one big game of Connect the Dots! And in the process they’re penetrating the clay soil and leaving behind organic matter will keep the clay broken up and full of nutrients.
This is by far my favorite method of amending clay soil. I currently started a vermicomposting bin/worm farm for this purpose. More updates to come!
If you can’t dig into your clay soil at all, try placing your citrus tree’s root ball on top of the ground and building a large mound of compost and rich soil around it. It should be stable and well-draining enough for the tree to grow. Over time the tree’s roots will penetrate into the hard clay and start working its way down into the ground.
You can also use this same method, but place your tree in a raised bed.
If you’d prefer to dig into the hard dirt still, use a pickaxe to break into it. It will be a lot of work, but it will allow you to plant the root ball in the ground.
Clay can be the hardest to break into when the sun bakes it. To prevent this, provide a mulch of leaves, grass clippings, and compost to protect the ground. Wet clay is much easier to dig into and amend than dry clay. Not only does it make it easier for you, but it also makes it easier for the roots and worms. Additionally, mixing these same mulching ingredients into clay soil are great amendments that will break down and will improve your soil within just a couple months.
A small section of amended soil in my parent’s garden.