High density tree planting, where two or more trees can be planted in the same hole to form a single canopy with multiple trunks, is drawn from the system of Backyard Orchard Culture, developed by the Dave Wilson Nursery of Central California.
In this system, fruit trees are kept small in size by planting them closer together, and by summer pruning them. This creates a high-density planting which provides many benefits, such as:
- Optimum use of limited space – many small fruit trees can fit in the space that one large fruit tree would normally occupy.
- Greater variety – when space is used more efficiently, more types of fruit trees can be grown, or more varieties of the same fruit which can serve as pollinators to maximise yields.
- Sensible production – smaller trees can produce a large enough crop to provide for a family’s needs, without the excess and waste.
- Extended harvest season – in the same space as a single large tree, a high density planting of early, mid and late varieties of one type of fruit can be planted, or various different kinds of fruit with consecutive harvest periods throughout the year.
- Easier fruit harvesting – when trees are kept as high as our arms can reach or a little higher, fruit picking is much more convenient.
- Easier orchard maintenance – low fruit trees are much easier to spray, prune and net, and they requiring far less effort and materials to maintain, and eliminate the need for specialised equipment such as ladders, pole pruners and long-reach fruit picking equipment.
How Many Trees Can Be Planted Together in a Single Hole?
It’s possible to plant two, three or even four trees into a single hole using this many-in-a hole Backyard Orchard Culture planting system.
When selecting trees to plant together in a high-density planting, it’s essential to select trees of similar vigour, to make pruning more manageable and prevent one tree from crowding out its companions.
Pictured below are two young fruit trees, planted two-to-a hole, and spaced 45cm (18”) apart. They will eventually grow into a single canopy, but with two separate trunks, which is far more resilient than a dual-grafted tree, because there are two whole root systems supporting tree-sized canopy.
How Far Apart Should Trees Be Planted in a Many-to-a-Hole Trees Planting?
In high-density plantings, the closest that trees should be planted is 45cm (18”) from each other, and no closer. The furthest they should be planted apart is 90cm (36”), as any further, and they will simply grow as separate trees, each with their own small canopy, if they’re summer pruned to dwarf their growth.
The same distances are used whether there are two, three or four trees planted in the same hole, and also if trees are planted together in a line to form a hedgerow, or if each tree is pruned into a columnar cordon form.
Can Trees Be Planted Closer Than 45cm (18”) in High Density Plantings?
In high-density planting used in Backyard Orchard Culture, the recommended planting distance is 45cm – 90cm (18” – 36”).
Why not plant trees closer than 45cm (18”) from each other?
I’ve seen a few instances where it’s been recommended to plant trees very close together, which is a very bad idea for two reasons:
As trees grow, their trunks progressively thicken. If the trunks touch, the bark will scrape as the trees sway in the wind, or they will fuse together in a form of graft. If bark is damaged, it creates an entry point for diseases and pests. If trees fuse together, any disease in one will spread to the other. Furthermore, if there is a narrow crevice between two closely-growing tree trunks, debris can gather there, and wet organic material can rot and cause the bark to rot away also.
The second reason is structural, as shown by the diagram below. When trees have a bit more space between them, there is more space between the two trunks for the canopy of each tree to grow into, moving more of the weight of the canopy a bit closer to the middle.
If trees are planted very close together, there is very little space between trunks for the canopy to grow into, so most of the canopy will hang off to one side, making each tree extremely lop-sided, with very uneven load distribution. A tree canopy heavily weighted to one side is prone to being blown over by heavy winds, or collapsing under increased canopy weight due to a heavy crop load. A wet canopy is heavier than a dry one, and the combination of rain and wind can have a similar detrimental outcome.
As additional reference, I’ve included a copy of the original document “Backyard Orchard culture (Summer Pruning Fruit Trees For Size Control)” by Dave Wilson Nursery, which, in case it ever becomes unavailable, can be viewed or downloaded here.