Central leader vs. open centre

I note that the Brits consistently train their semi-dwarf and full-size apple trees to an open centre, while the gospel in North America is that they should be central leader. (High-density supported plantings are a completely different beast, with techniques specific to them.) Just reasoning from the concept that we want maximal light exposure to all parts of the tree, plus keeping the bearing area within reach of the ground, it seems to me that a "flattened" saucer shape should be preferrable to something in which growth above inevitably shades the parts below, while growing progressively farther out of reach. What is wrong with this reasoning?

I am coming at this from the perspective of someone who has managed to do pretty much everything wrong in the early years of establishing my orchard. While I was aiming at establishing a modified central leader shape, many of my older trees have taken matters into their own hands and bent their leaders over to gentle arcs headed back down towards the ground, ending up as very lop-sided open centres.

Just in passing, I have a hazy recollection from 50 years ago of an account of apple culture in some very far northern country in which the trees are trained to a continuous low carpet a couple of feet high, wherein they are protected from winter damage by the snow cover. But this may be a figment of a dotty old man's imagination...

Broomholm Orchard
Zone 5b in Nova Scotia

Great point David. I too have ended up with rather exotic shaping of my trees and find that a somewhat open center is a very appropriate way to have a lot of production without losing sunlight on the various limbs. Plus it's very fun to climb on these jumbo jungle gyms during pruning time--great acrobatic exercise.

Having an open center without question allows for maximum light penetration and highest fruiting within this scaffold area. The issue as I see it is that this space becomes your cropping limit. A true central leader tree, particularly on the more vigorous stock, allows many scaffolds, and thus a considerable higher cropping potential. Certainly there is greater shading within each scaffold than you would find compared with open center, but you get more of them. Many growers in Europe and in North America traditionally went for these forms for ease of management (like spray coverage efficiency). But for highest yield, per tree, a larger central leader with multiple scaffolds wins out, especially for cider production.

The other issue is tree strength. A branch obtains some strength from the overlapping sheets of cells when both trunk and branch lay down their secondary growth each year. When trunk is absent above a branch, as in open center management, the branch stability is compromised. This doesn't necessarily spell disaster, but it certainly increases the possibility. Cropload, snow, etc, can tear these branches like a peeling banana in my experience. So, if folks are experimenting with this method, a subdued central leader without additional scaffold branches should be allowed to grow to strengthen the sidebranches below.

The bent leader is usually the result of leader cropping. Most suggestions are for the leader to be stripped of fruit to disallow this. It does, however, subdue the vigor, keeping the tree lower without cutting that leader. If allowed to grow too large, it of course shades the tree, but we are not supposed to allow this to happen.

A point I like to offer to folks these days is that the tree is a pretty nice vehicle to effectively increase food and organic matter production in the landscape. It beats all other forms of vegetation simply due to its aerial space occupation. By letting a productions system like the tree explore a maximum area, we increase production. This includes the crop of course, but it also mines nutrients from air and soil and deposits them as litter and prunings, thus increasing topsoil, mulch, and btu's for the farm. A plant, be it an herbaceous species, or tree, is quite limited in these possibilities when it is forced to maintain a particular height.

So, with proper management, there are probably hundreds of systems, the open center included (look at what the Japanese were doing in the 1800s with their high density opencenter production if you want to see something really cool), that can be done in a satisfactory way. If an orchardist is willing to take the extra time to monitor for potential breakage, because they want ease of spraying and harvesting it makes sense in the same way farmers engage in the upfront costs and management particulars of high density trellis growing. But, for maximum production of organic matter, carbon sequestration, wildlife habitat, minimum ammendment input, and yield per tree in the ground, the larger sized central leader tree is the best option.

Walden Heights Nursery & Orchard
Zone 3 in Vermont