Building living tunnel greenhouses for rural people in the drylands
Originally published at:
https://wordpress.com/post/desertification.wordpress.com/28530
By Prof. Dr. Willem VAN COTTHEM
University of Ghent, Belgium
One of the biggest problems for sustainably constructing greenhouses in the drylands is that of the strong winds. Most of the existing greenhouse constructions in developing countries do not resist these winds and the recurrent need to invest in reparations discourages those who see greenhouses as a valuable tool for sustainable economic development of the local people.
It is my sincere conviction that a good solution for this problem can be found in switching from man-made constructions with greenhouse frames (metal or bamboo) to “living greenhouses” with poles (stems) of growing trees.
In every single region on earth one can find (or introduce) easily rooting tree species. For some of them it suffices to directly planting cuttings in the local soil to get these cuttings rooting and developing after a while. One of these trees species is the Chinese willow (Salix matsudana) of which a number of varieties are grown all over the world, even in the desert, e.g. the Navajo willow (Salix matsudana var. Navajo), growing in Arizona.
Having in my garden in Belgium a couple of these willows, I developed the idea that with some cuttings I could “construct” a long living, sustainable “teepee”. Within a very short period such a shady little tent (a greenhouse) was grown:
The 3 meter long branches, used as teepee poles, soon developed numerous lateral branches, some of which were cut off and planted nearby to produce new poles for a second, a third, a fourth, … teepee in the future.
It goes without saying that cuttings of this Chinese willow can also be planted in two lines, e.g. over a distance of 50 meter with a cutting every 50 cm, to form a tunnel greenhouse. One can easily let these willow cuttings quickly grow into a young tree, pruning them into vertical poles.
Once these poles in the two parallel lines are high enough, one can bend them towards each other and bind their tops to form a “living tunnel”. Lateral branches, reaching a length of e.g. 30 cm, are pruned, except those in the plane of the tunnel walls. One can even “weave” these lateral branches into a strong network.
The canopy of the tunnel is filtering the heavy sunlight and air humidity inside the tunnel is higher, due to the transpiration of the leaves. These natural conditions (shade and humidity) are most profitable for growing plants, e.g. vegetables and/or herbs inside the tunnel.
Living tunnels can be used as a nursery for the production of hundreds (if not thousands) of saplings from cuttings. But they can also be used as a shady kitchen garden in which numerous food crops can be grown in containers, e.g. in bottle towers (see<http://youtu.be/-uDbjZ9roEQ>) with less water than the volume of irrigation water normally used on open fields, with irrigation in the morning and the evening.
Once a single living tunnel greenhouse exists in a location the construction of new tunnels is unlimited. It suffices to make the right choice of a tree species that is adapted to the local environmental conditions, easily rooting and developing relatively quickly.
The Chinese willow (Salix matsudana) is one of those species easily adapting to different types of climate. I got mine from the drylands in Arizona and it is growing remarkably well in Belgium. My 2 cuttings (30 cm in 2003) are now in 2016 12-14 meter high ! I would recommend to use the Navajo variety of this Chinese willow (Salix matsudana var. Navajo), a drought-tolerant variety growing in desert-like circumstances, only needing a minimum of water.
Anyway, whatever the tree species chosen (preferably an easily rooting local one), I am quite sure that it must be feasible for all the rural people on earth, to set up their own “living teepee” or their “living tunnel greenhouse”. The choice is theirs.
It would be a fantastic tool to combat malnutrition or hunger.
Please have a look at my video: https://youtu.be/DV23c6neIGg
“No more plastic greenhouses or tunnels needed : grow your own live greenhouse (a tipi/teepee or a tunnel) with branches of the drought-tolerant Navajo willow, also globe willow, or the Chinese willow (Salix matsudana). One can grow these willows with a minimum of water in the drylands, even in the desert.
Such a live greenhouse offers remarkable advantages : natural shade and higher air humidity inside because of the transpiration by the leaves.
In drylands or deserts people can easily grow plants, e.g. young fruit trees and vegetables, inside the greenhouse, which can also offer shelter against the sun heat.
Outgrowing branches of the willow can be pruned to construct progressively new greenhouses.”
DESERTIFICATION 
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