What is an arbustum?
In the autumn of 2019, when many wooden support posts in our vineyard were broken by the strong wind, a thought process started in our mind: what if we could make the support of our grapevines with living trees?
Naturally, a project like this raises many questions, more than we could answer. We started our internet search and discovered that the idea of trees as a support for grapevines is an ancient principle already applied by the Romans and known as 'Arbustum', 'Piantata' (Italy) or 'Joualle' (France). At the time, the grape vines were planted next to existing trees and thus grew to great heights via the branches of the trees. This made harvesting the grapes very laborious and sometimes even dangerous, as illustrated here.
The benefits of an arbustum
Enough reason to take a good look at how we could optimize this system. We arrived at the 'ARBUSTUM-Projekt', which was set up in 2005 in the village of Ayl, near Trier in Germany. In this project, a trial vineyard was established by the University of Freiburg and seven local wine estates. The effects of agroforestry on the growth of grapevines and trees (competition) were investigated, but also the quantity and quality of the harvest were analysed. In this vineyard, a fast-growing with a slow-growing tree species was compared, the poplar versus the oak. During the two years of research it was found that the presence of trees in the vineyard had a positive effect on water and nitrogen availability of both trees and grapevines. Therefore, there was no competition, but symbiosis. The different cultivation methods did not result in significant differences in wine quality in these two years. The full study is available here.
Viticulture and climate change
An arbustum proves to be of great value in climate change. After the summers of 2019 and 2020 were very dry and hot, the arbustum in Ayl proved to be much more resistant to crop loss due to sunburn than the surrounding conventional vineyards, as Florian Lauer describes in the video above. Due to shadow effect, but probably also because of the better water availability for the grape in an arbustum.
A few months later, Pius Floris of Plant Health Cure pointed us to a discussion that had been started by means of a newsletter by John Kempf of Advancing Eco Agriculture. John shared a photo (attached here) and wondered how the trees kept the grass below greener than the rest of the lot. Pius had a plausible explanation and showed us a piece of tree root that was porous. The core of the story: trees draw water up from deep soil layers, but release part of the water in superficial soil layers. This benefits the less deeply rooted plants growing near the tree. This can make a huge difference, especially in times of extreme heat and drought.
© John Kempf, johnkempf.com
Planting trees at Domain Aldenborgh
The summers of 2019 and 2020 were also a major challenge for our domain due to the drought and heat. Just like in Germany, we had considerable damage from sunburn. The multiple benefits the arbustum offers convinced us to plant one in the spring of 2020, next to our existing vineyard. We eventually chose the Turkish hazel, because of its climate resistance, its straight, continuous trunk without suckers from the base, fast growth and ability to pollard. Our goal is to prune the trees in the shape of a mop-head acacia, so that it is possible to harvest the grapes with a harvester. We will, as usual, use steel wire to run between the trees. The grapes therefore do not tend in the trees, but grow in the modern way between the wire. The trees will have to be pruned every year, but since this yields organic material that can compost on site, our vineyard will only benefit from it. We have planted 1800 small trees on three hectares and most of the vines are now also in place.
We see the arbustum as a logical next step towards an even more nature-inclusive cultivation, in which biodiversity increases as a result of the wooded environment. In short: a further refinement of our organic wine domain.
And now we hope for rapid growth!