Planting trouble: multiple trees in one hole

[I enjoyed Jeff’s Valentine story so much that I thought I’d stick to the theme of togetherness…for better or worse.]

A week or so ago a reader asked about the practice of planting three or four fruit trees in the same hole.  Having not heard of this before, I checked on the web and found many “how to” pages geared to home gardeners who either want a longer harvest of a particular fruit (early to late) or a mixture of different species.  Doesn’t it sound just great, especially for smaller urban yards?

One of these sites has these written instructions: "Plant each grouping of 3 or 4 trees in one hole at least 12 to 15 inches apart."

Now, I’m sorry, but this is just asking for trouble down the road.  Readers of this blog know that root systems extend far past the drip line, and that roots from different trees are going to compete with one another.  You’ll end up with three unhappy trees, all jostling for space and resources, just like kids in the back seat during those long car rides.

But wait! you might say.  There’s research on high density tree planting, and it’s been shown to increase fruit yield on a per acre basis! 

Yes, in fact there is a lot of planting density research on many different species of fruit trees.  What’s considered by researchers to be “high density” varies, but it rarely exceeds 2698 trees/acre (6666/ha for our international readers).  Optimal and sustainable levels of high density planting are also variable, as they depend on not only species but rootstock and the crown architecture; 1214/acre (3000/ha) might be a mid-range number.  This can be converted to a per-tree requirement of 36 sq. ft. or a 6’x6’ planting area.

How does this compare to the 12-15” recommendation given earlier?  If we’re generous and use the 15” recommendation, this translates to 6.25 sq. ft. per tree or 6970 trees/acre.  The 12” recommendation would lead to a whopping equivalent of 10,890 trees/acre.  (And no, it doesn’t matter if you’re using dwarfing rootstock or not; most of the higher densities in the literature are for dwarfing rootstocks.)

You don’t have to be a math whiz to see that these densities are totally out of line with reality.  Sure, you can probably keep overcrowded trees alive with lots of water and fertilizer, but they’ll be under enough chronic stress so that pests and disease might take hold, and fruit production will likely be poor.  And it’s about as far from a sustainable practice as you can get.

15 thoughts on “Planting trouble: multiple trees in one hole

  1. Great topic and I was going to ask the question myself. The information I was given by TreePeople here in Southern California was to plant four trees one at each corner of a 4′x 4′ square. They also mentioned that the trees should all be of the same root stock. The idea behind this was that the root stocks would not compete but “grow together” and form one large plant. Any truth in this advice?

  2. John, it’s possible that you wouldn’t get so much root competition if they did graft, but you’ll still have 4 trees, each with a quadrant of their canopy directly interfering with its neighbors. And each will be making demands on the entire root system
    for water and nutrients. The high density research I looked into generally deals with monocultural plantings of fruit trees (same rootstock), and you just can’t plant trees that closely together and not have them interfere with one another. The literature is pretty definitive in that respect. (At least the 4′x4′ hole is bigger, but it still works out to a density of 2722 trees/acre, which is significantly higher than what’s recommmended.)

  3. I would never plant multiple trees in one hole, but I’ve noticed nature does it all the time. Self seeding soft maples and mulberries are two examples from my own yard. The trunks seem to morph together making an interesting landscape plant.

  4. Jan, that can happen of course. But over time, most of the time, only the strongest survive and the others die off. It’s probably not a desired outcome for most gardeners.

  5. Brian, unfortunately the distances they recommend are too close for long-term tree health and fruit production. There are hundreds of studies on high-density planting and some of these are long-term. The science is pretty clear that planting trees too closely together will create problems after 5-7 years.

  6. I’m pretty sure the Sacramento County Master Gardeners have done this in their demonstration garden at Fair Oaks Horticultural Center. As far as I remember, it is all the same rootstock. Not that I’m an MG, but it all appears to working well (they’ve even got some neat examples of ladder-type grafting to unite the trees) with no problems. But perhaps that is because they’ve put the trees in large holes … and they are tended by MGs rather than the average homeowner.

  7. I once planted three peach trees in one hole. They stayed pretty balanced with a yearly dormant pruning. What put me off the practice was pest control. The early varieties were relatively pest free, but the late variety was too buggy to use.

  8. I’m glad I stumbled across this post. We were thinking of planting only 2 pear trees in one hole – no more than that. Would that still be too crowded?

  9. Judy, it depends on what you want. If you want small trees, growing them in the same hole will do that for you (since they will be competing for limited space, water and nutrients). Keep in mind that the half of each tree that grows into its neighbor is going to be more shaded and probably not very productive. You won’t double pear production as you would if you planted them apart.

  10. We don’t really care about the production – pears aren’t *that* good (!), but we needed a pollinizer. On the other hand, we really don’t want to do anything that will make the trees more disease/bug prone. hmmm. We’ll just do it the “old fashioned way” – and I’ve learned something to share with my clinic clients (I’m a MG). Thanks!

  11. Each tree would not get 12 inches, instead each group of 3 trees would get a 18 feet or 6 feet each which gives you the usual 1214 trees/acre.

  12. I don’t understand how you can reject an idea like this without first attempting it? Dave Wilson are long time growers and have had success with this method.

  13. Just freakin dig a 4′ diameter hole and toss 4 trees in it. Let us know how it turns out. Then we will have data on the East.

    I added a link that also advises against it without any evidence other than naysaying. Experiment. If it is really so bad you will know in 2-3 years and let us know.

    Remember roots are sluts…they will fuse with every other root and form a cohesive community underground AND competition is good to both control fruit tree size, produce more fruit per area/volume and produce fruit earlier in the life of a tree. Be nasty to your tree.

    Southern CA is different from most of the nation. Dry, hot, alkali and salty soil, low pest and disease, long season, mild winter, … how this effects BYOC needs to be studied in the east and the north.

  14. plant at outward angles, heavy summer pruning clearing out the middle area, keep height manageable. this is not a commercial orchard strategy nor is it designed to give max fruit/sqft, it’s a strategy to extend the growing season and to help with pollination for the backyard gardener. it takes MORE work.

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