IN DEFENSE OF TOPPED TREES
A Permacultural Perspective
Most arbourists these days will tell you that tree topping (the practice of pollarding large trunks and branches on mature trees) is an excessively destructive process: it’s largely been replaced in the trade with spiral thinning.
There are a variety of reasons for this advice against tree topping: all having to do with the long-term health and integrity of the tree. The caution against topping trees is relevant for gardeners, landscapers, horticulturalists, arbourists, and city planners, but not neccessarily a hard and fast rule for permaculturalists.
The reasons for this have to do with differing ideas about the function of a tree:
- In a heavily-landscaped garden or city street, there may be a few trees that constitute a significant investment, and the aesthetics and maintenance of those trees tie in to property values. Topping compromises the health and durability of the tree, which is fundamentally an economic concern.
- In the permacultural ‘food forest’-style garden I’ve built, I currently have 50+ fruiting trees, and I am planting and grafting new trees every day, so it’s not a big deal if one dies. I use pruned lumber for a variety of purposes, and sometimes I deliberately do things that impair the health of a tree – such as planting parasitic mistletoe – in order to create wildlife habitats.
Last year, I topped one apple tree, and did some drastic ‘spiral thinning’ on another. Both survived, with the topped tree sending up much-maligned water sprouts, and the spiral-thinned tree leafing out as usual (albeit with a little sun scorch on the leaves).
I’ve noticed that on the topped tree, fungus has begun to be established on the two stumps. Far from being dismayed by this, I am actually overjoyed! If you want to understand why fungus on my apple tree is welcome, look no further than the first picture accompanying this piece of writing.
Topping can stimulate the development of tree hollows, which are vital habitats for bees, beetles, birds, and tree-dwelling rodents like squirrels.
Tree hollows in living trees are cavities where the heartwood has been degraded by fungi or bacteria. Trees compartmentalise decay, and the only actively growing or vascular tissues of a tree are concentrated towards the bark. This means a tree can potentially be almost completely hollowed out, but still continue living.
Topping provides an opening for fungi and bacteria to create a cavity in the tree, and thus creates habitat. The excessive growth of water shoots is also a benefit, as timber is a valuable resource for mulch, hügelkultur, and carbon-sequestering soil building.
I’m doing my best to preserve these cavities in trees in the forest garden, even in trees that otherwise seem doomed. In the case of my European Ash tree with developing fungal lesions, instead of getting rid of the tree, I’ve done a bridge graft around the lesion. The hollow will continue to form, but the vascular pathways will remain intact.
Topping trees, like sheet mulching, can essentially be an accelerated way of promoting ecological succession in a forest garden. Fungi and bacteria also have a place in the ecosystem, and naturalistic garden maintenance means embracing those forces, rather than trying to control or eliminate them. We can always plant new trees, but bringing species back from the brink habitat loss-induced extinction is a little harder.
To me, local wildlife is included in the permacultural ethic of ‘fair share,’ as in, they too deserve a fair share of the space and harvest from this garden. You may be surprised at who moves in, when you make them welcome!