Even though I’ve planted many avocado trees, I was nervous putting in this little Jan Boyce, or JB for short (pictured on left). It is a particularly fine-tasting variety that I’d been trying to get my hands on for years.
But I needn’t be too nervous. I’ve already made most every mistake there is when planting an avocado tree; I know what not to do anymore. So here I write about how to plant an avocado tree with an eye toward avoiding common errors.
Testing soil drainage
How fast water drains through the soil in your yard is a vital piece of information to know because avocado trees are unlike any other in that they have a very low tolerance for their roots remaining soggy.
So what you should do before planting in a spot is test the drainage. You simply dig a hole about a foot deep and a foot wide, fill it with water and wait for it to disappear. Then fill it again and see how long it takes for the water to disappear this second time.
A rule of thumb that many avocado experts have used over the years is that it must disappear in less than a day, 24 hours. But really, if it takes more than about eight hours I think you’re in the danger zone and you’re going to have to be careful not to water too much too often. You’ll also need to make sure that winter rainfall doesn’t puddle around the tree. Otherwise, your tree’s roots will rot, its leaves will turn yellow and droopy, and you’ll have wasted your time. It probably won’t be apparent right away. It might not reveal itself until the end of summer or until the tree’s first winter.
Mounds can help. If your spot’s drainage is on the slow side, then build a mound of soil from 1-3 feet high and 4-7 feet wide (depending on how big the tree is) and plant the tree in the top of it. You’ve essentially created an area of soil with better drainage for your tree.
An avocado farmer in Ventura County lost a few trees to root rot (caused by Phytophthora cinnamomi) in his clay loam soil, so when he replanted the area he put the new trees on mounds:
(See more on this topic in my post, “Planting avocados in poor soil.”)
On the other hand, if you have fast-draining soil like me, where water drains out of the hole in less than an hour, then don’t bother planting on a high mound. If you did, you’d make it necessary to water even more frequently. In our case, plant level or only raised a few inches — unless your soil is shallow. If you hit rock or gritty subsoil only a foot down, do plant on a slight mound just to give the tree more good soil to root into.
Digging the planting hole
Dig a hole that is a few inches wider than the container. Do this so you can get your hands in the hole as you lower the tree and settle it in. There’s no need and no benefit of making the hole much wider. (One exception might be if you find many roots from other plants in the hole you dig, for example if there’s a mature tree nearby. In that case, you might dig wider in order to give the young avocado some space to itself before those plants begin re-rooting where you’ve planted the avocado.)
Also, dig the hole only as deep as the soil is in the container, no deeper — or even shallower if you’re planting on a slight mound. If you dig deeper, you’re likely wasting energy at best. You’re going to have put some dirt back into the hole, and later that dirt will compact and sink the tree somewhat.
Experiments have been done planting avocados in small versus large holes. No advantage has come from digging large planting holes. See “Avocado Planting Systems” by Ben Faber and G.T.A. Barnett.
Removing the avocado tree from the container
To get the tree out of the container there are different techniques according to the size and type of container. A little one-gallon like my Jan Boyce is easy. You just squeeze or slap the sides to separate the plastic from the roots, then tip the container and slide the rootball out.
Do this right next to the planting hole so you don’t have to carry it. Usually, the container mix is a loose mix and the avocado roots don’t hold it together well. The rootball tends to fall apart in your hands. So be prepared to embrace it and lower it into the hole immediately.
Avocado roots are brittle. They’re unlike other fruit tree roots. If you grab any while lowering the tree into the hole, they’re likely to snap off.
The most common size of avocado tree that we home gardeners buy in nurseries is sold in what’s called a five-gallon container. The process of removing the tree from a five-gallon container is the same as for my little Jan Boyce in the one-gallon container, but everything is heavier and more awkward. It can help to have a partner when sliding the container off the tree’s rootball.
The largest size that most nurseries sell is in a 15-gallon container. These trees are so big and heavy that they require a different procedure unless you’re The Hulk. What I do with a 15-gallon is cut the container off the tree’s rootball rather than slide it off. I lay the tree on its side next to the planting hole and, with a utility knife, slice down one side of the container and across the bottom. Then I roll the tree and slice up the other side. You can then pull the container off and slide the rootball into the hole. (It’s crucial to have made the hole the proper depth before sliding the tree in.)
Finally, there are also avocado trees sold in plastic sleeves. These are the easiest trees to remove from their containers because you can just use scissors to cut the sleeve, and the small rootball is easy to handle.
(You might like to read my post, “Should you buy a big or small avocado tree?”)
Filling the hole and watering in
At this point, put some of the dirt from the hole back in around the sides of the tree’s rootball, but only about half way. Then fill the moat with water. After it drains, tamp it down with your fingers to get air pockets out and settle the soil around the roots. Then fill the hole with dirt up to the level of the tree’s container mix, but don’t cover the container mix with dirt. If you do, it will be hard to get water through the dirt and into the container mix where the tree’s roots are.
Note that you’re only using your native soil to fill the hole. There’s never been any benefit shown in adding compost or fertilizer to an avocado tree’s planting hole. (This was studied and reported on in the same paper mentioned above, “Avocado Planting Systems.”)
That being said, I have seen avocado trees that have been planted in large holes and with compost added to the planting holes that have grown very well in their first couple years. It’s not that large planting holes and adding amendments are bad. It’s just that they haven’t been shown to give a tree any benefit when compared to avocado trees planted without those extras.
I like to build up a berm a few inches high around the new tree now. I make it a foot or two wider than the container was, and I add mulch. The berm isn’t necessary, but it makes it really easy to water in the tree right here after planting, which is necessary.
You want to water a lot on planting day. Along with testing the drainage, watering lavishly on planting day is the second very important thing you can do for your new avocado tree.
Not only do you want to water the tree’s rootball, which has been shocked by having its home removed and being placed in new surroundings, but you also must thoroughly soak the surrounding native soil because otherwise it will literally suck the moisture out of the container mix. Real dirt is able to grab and hold onto water better than any container mix. This is also the reason that you don’t want dirt covering the top of the container mix. (See photos of water’s movement, or non-movement, between native soil and container mix in this excellent article by Dani Lightle of the University of California’s Cooperative Extension.)
I fill up the basin, let it drain, and fill it up another couple times in order to soak and settle the planting area. You could also accomplish this watering with a sprinkler.
Staking the avocado tree
My little Jan Boyce didn’t come with a stake and it doesn’t need a stake. But if you bought a five- or 15-gallon tree, there will be a stake tied to it.
You cannot remove this stake and expect your tree to stand up on its own, nor can you leave the stake as is and expect the tree to grow a strong and healthy trunk. I’ll call this the third key to getting an avocado tree off to the best possible start to life in your yard.
Some years back, I broke my ankle. I was in a cast for some months, and then I visited my doctor and he took it off and told me to stand up. I was afraid. But he explained, “As soon as possible, you need to start using these muscles again so they will strengthen.”
The stake that is tied to your new avocado tree is a cast. It is tightly tied to the tree’s trunk, and it supports the trunk, but it also prevents the trunk from strengthening. The trunk can only strengthen if it is able to flex.
There are a couple of effective ways to restake your newly planted avocado tree. Most avocado farmers replace the nursery stake with a thicker, taller single stake (2″ x 2″ wood or 1/2″ metal pole), and the tree is tied to that — not more tightly than is necessary. I stake some of my trees like that.
Or sometimes I replace the nursery stake with two stakes inserted just outside the rootball on either side of the trunk. The stakes can be made of bamboo, 1″ x 1″ wood, metal, it doesn’t matter. Using one-inch nursery tape or something similar in size, I tie the trunk to each stake. (The tape can’t be too narrow or inflexible or else it will cut into the trunk as the trunk grows and moves in the wind.)
You want to tie the trunk to the stakes as low as you can without the trunk flopping over. If the trunk is already fairly strong, you’ll be able to tie relatively low. But if the trunk is weak, you’ll have to tie higher or even possibly tie at two levels.
With either staking method, you should frequently check up on the stake ties to see that they’re still holding the tree up correctly. Often they need adjusting.
In addition to staking, you may need to do a little training and pruning over the first year or two in order to balance the tree’s growth and help it stand alone and hold its first crop. A poorly staked and trained young avocado tree could end up leaning like my Lamb:
To avoid this, please see the suggestions and examples in my post, “Training young avocado trees.”
(Here is a video I made about staking avocado trees.)
After being watered in and staked, your baby avocado tree is ready to run. Just be aware going forward of a couple of important issues. One is sunburn. Exposed branches on avocado trees, including the trunk, are more sensitive to sunburn than any tree I know. Please read my post, “Avocado trees get sunburned — what to do?”
Also, if you’re planting in the summer, consider shading the new tree on hot afternoons for the first few weeks. By hot afternoons, I mean over 90 degrees. The reason this might be helpful is that often at nurseries trees are bunched together and shading one another, but you might buy and plant yours alone in full sun. This can add to the shock of transplanting. I’ve found that giving such a tree relief on a hot afternoon while it’s acclimating can avoid sunburned leaves during those first weeks. (See photos of shade structures in the above linked sunburn post.)
Secondly, even as watering avocados appropriately is important generally, watering avocado trees during their first one to two months requires extra attention. Once you get through this initial phase, your tree is resilient because it will have grown roots into the surrounding native soil. In the meantime, don’t slack. And for details, please read my post, “How to water a newly planted avocado tree.”
Finally, if your yard ever gets frost, be prepared to protect your young tree from any particularly strong cold spells in its first winter or two. This can be as simple as posting a beach umbrella over it for the night. For more on that see my post, “Protecting avocado trees from cold.”
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