My family in Orlando, Florida has a few avocado trees, some of which are pretty close to their house. They were wondering if they planted them too close to the house’s foundation, so they asked if I knew anything about it. To learn more, I did some research. Here’s what I found out about avocado tree roots.
According to California Polytechnic State University, avocado tree roots have a moderate to high potential for root damage. This risk can be reduced by choosing less invasive rootstocks and planting the trees at least 25 feet away from structures such as foundations and driveways. Root barriers and pots also help.
|Avocado Tree Variety||Root Damage Potential|
So, while avocado tree roots can have potentially damaging roots, exactly how long and deep do they grow, and what else should we know about their roots when choosing a planting site? Let’s take a closer look.
How Long Do Avocado Tree Roots Grow?
Generally, avocado tree roots grow up to 25 feet long, or about the length of the tree’s drip line. On the other hand, dwarf avocado trees have roots about 15 feet long. Because of this, it’s best to keep avocado trees at least 25 feet from structures such as fences, walls, and foundations to avoid damage.
The roots of avocado trees are responsible for gathering primary resources from the surrounding environment, such as:
Ideally, the best soil for avocado trees is one that’s loose, rich, moist, and has a slightly acidic pH of 5.0-7.0 (source). Soil that meets all three of these qualities will promote the best root growth.
The reason why avocado trees grow long roots is that the topsoil is where much of the nutrients and water is located. Additionally, by spreading their roots out, avocado trees anchor themselves from the wind and large herbivores.
However, avocado tree roots can have their growth limited by:
- Cold weather
- Compacted soil
- Lack of water
- Lack of nutrients
Compacted soil is common in suburban areas or construction sites and will give avocado trees a hard time growing their roots.
And this issue is made worse with heavy clay soils.
Compact clay soil not only makes it difficult for the tree’s roots to grow but creates poor drainage and high alkalinity, leading to poor nutrient uptake. Some acidity is needed to dissolve the solid nutrients and make them accessible to the tree’s finer roots.
This is why the ideal soil for avocado trees is loose, well-draining, and has a slightly acidic pH.
Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.Donald Bickelhaupt, SUNY College of Environmental Science and Forestry
If you’d like to learn more about planting in or amending clay soil, check out my recent post: Can Fruit Trees Grow in Clay Soil (& How Do You Plant Them)?.
If all of these ideal growing conditions are met, avocado tree roots can grow up to 25 feet long. But just how deep can they grow?
How Deep Do Avocado Tree Roots Grow?
Avocado trees have shallow roots, with 90% of the roots found in the first 2′ of soil and the rest reaching up to 3′ deep. While many factors contribute to the depth of avocado tree roots, the main ones are water, nutrients, and space. Avocado trees are unlikely to damage pipes but should be placed away to be safe.
Avocado tree roots grow to different depths depending on environmental conditions such as:
- Soil packing and quality
- Water content
Most roots are found close to the surface, with 90% or more of all roots located in the upper 60cm [24 inches].Martin Dobson, Arboricultural Advisory and Information Service
Generally, avocado trees have two types of roots: vertical and horizontal.
While the tree’s shallow, horizontal roots are effective at growing through the topsoil and gathering fresher nutrients, the deeper, vertical roots specialize in accessing deeper water tables (along with stored nutrients). These deeper roots commonly reach 2-3 feet deep, depending on their size.
Dwarf rootstocks feature an effective feeding root depth of 1-2’, while full-size trees probe 2-3’ deep.University of California, Santa Cruz, Center for Agroecology & Sustainable Food Systems
The deepest root is the taproot, which has the main function of establishing a foundation for the rest of the roots. The taproot is one of the first roots to grow and can assess the nutrient and water potency of the soil. It commonly grows to a depth of around 3 feet. If the taproot is damaged or broken, it’s unlikely to grow back and the rest of the tree can become stunted.
Since avocado tree roots are more invasive than other fruiting trees and can grow fairly deep and long, some gardeners are concerned that they’ll damage property. So, is there any truth to this?
Can Avocado Tree Roots Damage Property or Structures?
The roots of avocado trees are rarely the cause of foundation damage but can displace walls or fences as they grow. This is due to the shallow root systems that spread horizontally just under the surface. Avocado tree root systems are more likely to destabilize the ground than directly cause any damage.
While unlikely, avocado tree roots can cause potential damage to:
- Fire Hydrants
While most avocado tree varieties are listed with a “moderate” root damage potential, Hass avocados in particular are labeled as having a “high” root damage potential.
So, if you’re planting Hass avocados near structures or concrete, it’s a good idea to keep them 25 feet away, if not further.
However, avocado tree roots are not as strong as other, larger trees, such as oaks. For this reason, their roots are not likely to pose an issue compared to other trees.
The most likely scenario is the avocado tree’s roots displacing a light fence or wall as the tree is growing.
But what about water pipes? Don’t tree roots commonly grow toward them, and eventually break them?
In the book The Hidden Life of Trees, forest manager Peter Wohlleben busts the myth that a tree’s roots are attracted to water from water pipes. He writes that the more likely case why they’re attracted to the pipes is that they generally have looser ground, which allows for more air and space for root growth. Any water leaking from a pipe is more of a bonus.
However, if there is water under the foundation, roots can absorb this water and dry out shrinkable clay soils.
This indirectly causes damage by contributing to the depletion of soil moisture which can cause the foundation to recede into the ground. But this situation is uncommon and a foundation’s age is a more likely culprit in its damage.
Still, it’s better to be safe than sorry. Because of this, plant avocado trees away from structures if possible (especially the Hass variety).
How Far Away Should You Plant Avocado Trees From Structures?
As a general rule, plant avocado trees at least 25 feet away from structures such as foundations and walls. This will avoid any potential damage from the tree’s roots or branches. It will also ensure that the plant has enough space to grow and find sufficient nutrients in the soil.
When you’re planting your avocado tree, keep it at least 25 feet away from structures, but no more than 50 feet away from the rest of your garden. This is because other plants, such as flowering companion plants, can’t benefit avocado trees when they’re out of range.
Simply put, it’s not likely that pollinators, such as bees, butterflies, and hummingbirds, will visit both the companion plants and the avocado tree.
Speaking of companion plants, if you’re interested in checking out the 10 best companion plants for avocado trees, visit my recent post: The Top 10 Companion Plants for Avocado Trees.
Planting your avocado tree away from structures is the best way to prevent any potential root damage. However, what are some other methods of control?
How To Control Avocado Tree Roots
The best way to control an avocado tree’s roots is with a root barrier. You can also keep the tree in a raised bed or pot, or prune its roots. However, pruning an avocado tree’s roots can stunt the tree and is more upkeep than simply planting in a root barrier or pot. For these reasons, pruning is best avoided.
Generally, the best ways to control an avocado tree’s roots are with the following four methods:
- Root Barrier
- Root Pruning
- A Pot or Container
- Raised Beds
Root barriers are used to redirect the tree’s roots deeper into the soil and away from fences or foundations. This physical blocker protects your property as well as the avocado tree. On the other hand, planting the avocado tree in a pot naturally binds its roots.
Raised beds are often the most expensive item in the garden, but a little secret is there are some nice affordable ones on Amazon.
Keep in mind that avocado trees grow an average of 36 inches per year (source), so they can quickly outgrow their pot.
Because of this, it’s best to provide potted avocado trees with a new, larger container and fresh potting soil every 3-5 years. If you feel comfortable, you can also prune the roots during this time to slow the tree’s growth.
If you’d like to get an idea of a good root barrier you can use for your avocado tree, this root barrier on Amazon is a popular choice.