How do you graft an avocado tree? Click here
What is the best way to plant an avocado tree?
Give the tree what it needs: Good soil drainage, nearly full sun, ample fertility. If your planting site is a light sandy soil on a slight slope, you can ignore much of what I’m about to say about building mounds. For everybody else with even suspected drainage issues, invest the time and build a mound by mixing washed coarse sand or decomposed granite into the best, lightest surface soil you can scrape-up. If your soil is very heavy clay, use lots of sand! And no, it is not okay to dig a hole in the clay, fill it with sand and put your tree in it. Given a little rain, that results in a small pond with some sand and a dead tree in it. This the opposite of what you want to do. For terrible heavy clay soil, the idea is to create a slight mound of the natural soil, not a depression, then add to that natural mound your light, well draining material. You are importing artificially porous substrate, elevated above your natural grade, upon which to grow your tree. Imagine the root spread of a mature tree, and start building a mound that extends that far now. Regardless of what you think you know about phytophthora resistant root stocks, planting into perfect soil or a robust (18 inch tall, initially six feet across) planting mound is your best insurance against root rot; skimp at your own peril.
Avocados are best planted from March to June, when the nights are no longer frigid, the soil has warmed, but before summer air-temperatures have turned blistering. Prepare your mound and dig a hole in it so that the bottom of the root-ball sits at or above natural grade. Set the potted tree in the bottom of the hole, gently slice the plastic grow-bag in-situ, carefully peel it off and remove. Fill in around the root-ball about half way at first, add water to wet thoroughly, then fill up around the roots and water again. To get the best growth, be gentle, don’t tweak or in any way damage the brittle young roots. Do not break up the root ball (!) as you might with some other type tree. Also the soil in contact with the root-ball should be free of wood chips, leaves, grass, any other uncomposted organic matter, fresh manure, or fertilizer of any kind. The ethylene gas given off in the break-down process is toxic to roots. All those things can and should go on top or on the sides of your mound, but not ever in contact with the actual roots.
Don’t bury the top of the root-ball, but leave a lip raised around it, creating a slight basin (about a foot or two across) to irrigate into. Cover and support the new mound with lots of mulch. Six inches deep is a good start. Before you cover everything in mulch, stand back and take a look at what you’ve built. If your mound is smaller than you’d like, use more gravely sand, go buy some if you don’t have any around, it’s cheap. If you don’t have a truck to haul it, buy it in buckets and put them in the back seat! Continually add wood chips and mulch over the top and around this highly-aerated, super well-draining foundation. Over time, the organic material will break down into the nutrients and moisture holding material your avocado needs.
Does that sound like a contradiction? Lay down an austere, gravel foundation, so it drains perfectly, then cover it with organic material so it holds water? You want the root-zone to drain through the bottom, so the air in the soil is never completely displaced by water, but you need the mound to be protected from evaporation and surface drying. Since the avocado has really shallow roots (90 % of feeder roots are within 6″ of the soil surface), thick surface-insulation is crucial. It keeps the soil/mulch interface continuously moist, cool and hospitable to root growth. If the root-zone dries out, your tree goes into shock.
For fertility, it’s helpful to layer composted horse, cow, or goat manure into the mulch, so it can be watered into the root-zone. Don’t feel like you need to mix a bunch of compost or manure into the dirt, just make sure your mound is porous, so the “tea” leaching from the rotting mulch and manure that you have piled on top of everything, feeds your tree.
A more direct way of perking up yellowing, stalled out trees is to use a tea made of composted chicken (or other) manure. A small shovel full of the shit swished around in a five gallon bucket makes a good drench for the root zones of those problem trees. Once a week during the growing season should turn things around. If you see browning at the leaf edges, back off, that means the salts in the manure are starting to damage your tree.
Five to ten pounds of gypsum scattered (upon planting and annually ever after) over the surface, then watered into your mound takes up salts, and is an effective incantation against (Phytophthora c.) root rot. Water the new tree thoroughly upon planting, and lightly, twice a week (to keep the whole mound damp but not saturated) through the first season.
Sunburn is a common cause of death for young trees, so prevent it by painting exposed trunk bark with white interior latex paint diluted 50/50 with water (a light fabric shade-cloth suspended above the plant on a large tomato cage is also effective). Shades open on one side do a good job of not accumulating too much heat.
It’s also a good idea to bury a three or four foot stick of bamboo, 1/2″ thick, next to the root-ball when you plant your tree (not through the root ball!), then loosely tie the trunk to it in a couple places. I didn’t do this and an unexpected wind storm broke-off the 1″ trunk of my spring-grafted but gorgeous 5′ tall Edranol tree last fall. A stick and two pieces of string would have saved it, and as you can tell, I’m still a bit bitter about it.
Will the cold kill my avocado?
Maybe. Let’s face it: planting avocados is a form of gambling. Here on the central coast, roughly once every ten years come winter low temperatures that would kill any unaided young avocado tree. It thus becomes the growers’ job to cheat the dealer by doing the things necessary to protect the tree.
1. Choose varieties wisely. Sadly it’s like this: the more delicious the avocado, the less hardy it will be. So plant something tough (Mexicola, Zutano, Bacon) for insurance, and then gamble for flavor: Tender varieties like Queen, Sharwil, Greengold, Edranol, Nabal, Nimlioh and Malama lie a little on the risky side of the spectrum, while Hass, Lamb, Pinkerton, Gwen, Reed, Bonny Doon, Palo d’Oro (also all delicious), are in the middle somewhere . Read the blog piece about what variety to plant in you yard.
2. Plant wisely: Give the tender varieties the most favorable locations.
3. Grow the trees hard. Size matters when it comes to cold tolerance. The bigger the trunk diameter, the more cold a tree can take. This means even moisture levels, copious mulching, manure tea, and horse manure!
4. Protect the graft union! When a cold spell hits, the most important thing to do is insulate the graft union (the point at the base of the tree where the root-stock was joined to the scion variety that grew into your tree). Use straw, sawdust, coffee hulls, burlap sacks or rags, etc. Insulate thickly to 10” above the graft. This way, if your tree melts down in the cold, the graft will survive and will grow back quickly. It may be ugly for a few months, but it will blast back into growth when the weather warms, and look great by Fall. Don’t forget to remove the insulation after the cold snap has passed.
5. Cover your tree to hold in ground heat. Floating row-crop cover works well, but so do old sheets, shower curtains, plastic bags, etc. And if you want extra insurance, run a short string of large bulb (5 watt) Christmas tree lights up the trunk. That small increase in temperature in-close may be all the tree needs to survive.
Can I plant an avocado tree from seed?
The answer to the question is yes, but you probably don’t want to. All avocado varieties grown commercially like Hass, Bacon, and Fuerte originally came from a tree that was grown from a seed. That seedling was discovered, recognized as a variety worth cultivating, then reproduced through grafting to make millions of trees that are all copies of that original seedling tree. Your avocado tree grown from seed may in fact produce a bounty of delicious avocados. Unfortunately, the odds are against you, and you’re likely to end up with a tree that produces inferior fruit, if it ever produces at all (50% odds of being an unproductive B type), and you’ll typically wait ten to twenty years to taste the first one. The varieties grown commercially have characteristics selected from an enormous gene pool that contains many negative characteristics: stringiness, large seed, uneven ripening, intolerance to Phytophthora (a fungus that causes root rot), poor flavor, a tendency to not flower or produce fruit until years after planting, poor bearing characteristics, etc. With this said, your beloved seedling could still grow into a tree that produces exceptional fruit at a young age, but that would be bucking odds. You’ll likely find yourself wishing you had planted a recognized variety that would be lovely and ornamental as well as delivering a delicious harvest. If you end-up with an unproductive avocado tree, seedling or otherwise, don’t despair: Saw it down no matter how big it is, and use it as a root-stock and have someone graft it over to something you want. You could be eating great avocados in a few short years.
Can I plant an avocado tree in a container?
Maybe. Some varieties like GEM, Reed and Palo d’Oro are somewhat self-dwarfing, and can in theory be kept in a container. But it is a little like asking if you can keep an eagle in a cage; it is going to take a lot of work and it may not be very happy. I don’t think I had ever seen a bearing avocado tree in a pot (outside of a nursery), until recently.
The problem with potted avocados are several:
Avocado trees love to grow and spread out their feeder roots wide along the soil surface under a layer of mulch. Pots are inherently limited in surface area, by definition confining the roots.
Soil in pots fluctuate in temperature and moisture more than an equivalent natural situation.
Potting soil often contains fir bark or wood particles which decompose and cause several problems:
The break-down results in a denser, mushier, sludgier mix that holds onto water too effectively, leading to overly wet roots.
Microbial activity competes with your avocados roots for the oxygen present in the soil, and the denser structure of old mix provides less space to hold oxygen. Anaerobic soil is tolerated well by some plants, but not by avocados. Their roots exhibit high rates of respiration, and suffer from a lack of the air they need. And yes, roots of plants breathe in oxygen, even though the leaves take in CO2 and exhale oxygen.
Composting organic matter also produces ethylene gas, which is toxic to roots. The finicky roots of avocados are especially sensitive to everything, including this.
So we have strongly discouraged the idea that you could keep avocados long-term in pots, until recently.
Several of our customers have forced us to reverse this position.
Sometimes its empowering, eating a little crow.
We were shown that if you use a very porous soil mix with no organic material incorporated besides maybe a little portion of peat moss (which is stable and slow to decompose), the soil will not compact over time, and will maintain a well-drained oxygen permeable substrate for the roots to thrive in. We hope to have a new page on our website providing a recipe adapted from the various potted-avocado pioneers who have been informing and advising us. On that page, we’ll include a photo series of our components and mixing process, plus an actual pictorial progress report of our trial trees over time.
We’ve seen some busting, productive trees in containers, hope our little experiment doesn’t disappoint.
I only have a small space. Should I consider planting an avocado tree?
If your small space has full sun and the possibility of good drainage, then go ahead and plant an avocado tree. You’ll need a least 6’ square. There are several varieties that are either naturally dwarfing or are columnar and can be kept small. The Gwen, Gem and Reed are three are particularly suitable types, since they partition their energy into fruiting instead of growing. All avocado trees can be pruned to keep their size manageable, but this can impede productivity. Pruning is done anytime, but best just after a bumper crop comes off the tree.
Do I need to plant more than one tree for pollination?
Nope. All of the older literature insists the necessity of having two trees, but it’s now been shown that in many places the avocado is self fertile, and doesn’t need a pollination partner. It does depend on where you live, as temperature and humidity play a role. To read the whole story, see our Pollination blog from Feb. 2019.
How should I feed my Avocado tree?
To grow an avocado tree so it really kicks in, follow the planting instructions, then fertilize monthly with a slow release type organic fertilizer. No bat or seabird guano, no fresh chicken manure, or anything else that will dump a load of nitrogen and salts into your tree’s root zone. Alfalfa meal, chicken feather meal, horse manure are great. Composted goat, cow, chicken or rabbit manure can be used with discretion. Horse manure, perhaps the perfect avocado food, can be lavished: a wheelbarrow full for each three feet of tree height isn’t too much.
If you aren’t that handy with a wheelbarrow, use a slow-release bagged/boxed fertilizer blend like True 4-4-2, Sustane 4-6-4, or a similarly numbered blend from someone else. Spread the fertilizer evenly on the surface, around the perimeter of the tree, away from the trunk, out in the drip-line. Renew the “manure” and mulch in your mound often (once every couple months) all through the growing season. Avocados take-up nitrogen most efficiently in the summer, so this is the time to push it, but having your tree well fed into the fall seems like exactly what we’ve always heard one should not do: “Generating a flush of tender growth in the fall will only provide more fresh wood to be slaughtered in the first hard freeze.” Leaves of avocados with high nitrogen levels have been shown to tolerate lower temps with less damage than leaves with low levels of N. I have seen what happens in my yard. Avocado trees I’m really babying (feeding into the fall) continue growing right through all but the coldest spells, and when the hard freezes come, the tenderest tips burn back on even a protected tree, but resume growth as soon as the weather warms. The unfertilized tree gets burned also, but doesn’t recover as readily. I’ve never quantified the difference, and too disorganized to ever even think of testing for nitrogen levels, but the net effect is clear: a fertilized tree comes into spring bigger, in better color, and more ready to grow than the one skimped out on the previous fall.
My avocado tree is not growing, and the leaves are yellow, how can I help it?
People send us a lot of pictures of sick avocado trees. They can go wrong in so many ways, it’s hard to know where to begin.
If the tree was planted into soggy or clay soil, or over-watered, or under watered, or manhandled before planting so as to damage the roots, or sunburned horribly through insufficient protection, it might be time to try again. These kind of terminal cases can be identified by near total loss of leaves, necrotic, blackened stems, and progressive die-back.
If the tree has simply stalled-out and looks tired, there is more reason for hope.
If the mound looks nice and big, and the tree has been watered judiciously, and it still looks weak, the first thing to try is to give it some fresh nitrogen. Slow release blends like True 4-4-2 are ideal. A quart, evenly distributed around the drip line is a good amount for a newly planted tree. If the N number on your blend is higher, reduce the quantity proportionately.
If after a few weeks, that produces no positive effect, it indicates the roots are damaged, and aren’t strong enough to support the canopy. Cutting back the top of the tree might help.
This is the most counter-intuitive measure, the exact opposite of what you hope for when growing a tree, but anytime your avocado looks bad, and does not respond to even water and steadily renewed fertilization, reducing the ratio of top to roots can be part of the solution. Even if the tree is dying of root-rot, cutting it back can keep it alive a little longer. If it’s gopher damage or heat or drought that’s dragging your tree down, reducing the top can turn it around and get it growing again.
If feeding and watering and cutting it back produce no change in the tree’s condition, the planting mound should be eyed with suspicion. There is no remedy for bad soil. The price of a dead tree is often a reasonable tuition to pay on the avocado learning curve. In my yard if a tree dies in a specific location, planting another one in the same place usually gives the same result. I attribute this to accursed ground, and try to appease the fairies by digging the soil and laying stuff from around the root-ball way out on the periphery, away from contact with the new tree, and being generous with a new load of fresh material for the replanting mound.
I find that regardless of what I know about avocado root requirements, I have tended to underestimate the drainage needs of my trees, and when I dig up a dead one, it has invariably been underlain with thick spongy, gummier-than-I-thought-possible soil. Its then that I can hear that voice in the back of my head saying “Duhhhh, no wonder this thing died!”
