Planting is traditionally done with 2 metre spacing, providing each tree with a tube shelter and stake. This is the method advocated by the forestry commission and is based on the desire to create straight stemmed crops to harvest. The tubes protect the trees from animal browsing, and act as a vertical greenhouse, creating optimum conditions for trees to grow into straight specimens.
We are planting for carbon sequestration, flood mitigation and biodiversity. Trees that are not straight specimens is the desired outcome; we want them to look as natural as possible. Damage from predators, so long as it does not kill the tree, adds to the naturalness of the final woodland. Many species naturally coppice after being browsed or barked and grow back multi-stemmed, often more resilient.
We don’t use tubes or stakes; we plant larger numbers of trees in dense clusters. The reason we don’t use tubes is:
- It’s an exposed, windy site and the tubes would increase the wind resistance of the trees and make it more likely they would be blown over.
- Trees grown in tubes in windy locations tend to snap easily once they out-grow the tubes.
- There is a large amount of embodied carbon in the plastic and stakes; we plant trees for carbon capture, so they set off at a deficit if planted with tubes.
- Access is difficult; it would be hard to get tubes and stakes on site and even harder to remove them once the trees had grown.
- We plant into bracken and other tall vegetation, and tubes would increase the light deprivation of the trees.
- They cost more money and time, and for the same cost we can plant five times as many trees.
- They are unsightly, and we are planting in a visually sensitive landscape in the Lake District National Park which is a World Heritage site.
There are, of course, some disadvantages to not using tubes and stakes. We plant into bracken, without controlling it first. The bracken provides high quality humus soil, and in the summer protects saplings from dehydration. However, the bracken grows bigger than the saplings and overshadows them, depriving them of light. If the trees are in a tube this can be a problem, but without a tube the sapling puts out more lateral branches and these enable it to take maximum advantage of the restricted light. We have also noticed that the leaves turn much darker green, so the plant creates higher levels of chlorophyll to combat the low light levels. The leaves stay green longer than the bracken, giving the trees an opportunity to put on another growth spurt in the autumn. The trees produce leaves and start growing earlier in the spring than the bracken. Within a couple of years the trees outgrow the bracken, by which time they in turn deprive the bracken of light and eventually the bracken dies back, giving way to the woodland plants that have been waiting for the woodland to return.
There is a concern that bracken will crush the saplings when it dies back in the autumn. However, by planting in dense clusters of mixed tree species, the saplings support each other against the weight of the fallen foliage and protect themselves from being squashed.
Cluster planting replicates the way trees naturally re-colonise in the wild. The trees compete with one another but protect each other too, sharing nutrients and sheltering one another from predators. We plant in random shaped blobs a few metres in diameter (not wall to wall trees, that would be extravagant indeed!). Woodland edges tend to be where biodiversity is greatest, so planting in clusters creates a lot of edges.
The main disadvantage for us of not using guards is damage from voles. However, voles can get under regular tree guards. We do sometimes use vole guards, but on the whole we do what we can to encourage natural predation, such as erecting owl boxes and raptor perches.
We are lucky enough not to have had any rabbit damage at any of our sites. A great many of the trees are snipped off by hares (they don’t even eat the trees, just snip them in half as though irritated by their presence!). What we have observed is that the trees actually grow back more vigorously after the hare-snip so we stopped being concerned about that. And deer, well, they can be annoying. Again, a bit of browsing doesn’t matter at all, the trees will produce more leaves. The barking by the bucks can be very damaging but the advantage of planting in dense clusters is that the bucks don’t get through to the trees in the centre of the cluster. The edges that are barked sometimes coppice themselves, depending on the species of tree. And again, if the trees are planted in dense bracken, the bracken protects the trees in July when it’s the roe-deer rut. It’s a different matter with other species of deer, or other locations, but on our sites cluster planting without tubes or stakes has been successful.
Just as trees compete and collaborate in the wild, our densely planted saplings do too. There’s an element of attrition built in to this way of growing trees.
