The Agroforestry Research Trust is the creation of Martin Crawford, a man who seems to possess indefatigable energy and ability. A drive through winding Devon lanes took the course to his Littlehempston site covering eleven acres near Totnes.
 His best known site is the two acre forest garden he has developed at Dartington Hall over a period of twenty five years. I wrote an entry about it recently (February 27th.) with examples of some of the general principles of forest gardening and Permaculture's ethos of creating food forests which generate a "permanent agriculture".

 Littlehempston is a somewhat different proposition and work began in 2011. It contains two new forest gardens, various large scale experimental plantings, nurseries and propagation beds and most intriguingly a sub-tropical forest garden greenhouse (as seen at the far end of the photograph above). It's pretty big as greenhouses go- intended to allow trees that grow as tall as six metres. 

  

 "Futuristic" is a word that doesn't seem entirely out of place here. The temperature is maintained by a 'climate battery'. In so far as I understand it the warm moist air of the daytime is circulated through underground pipes by fans warming the soil by conduction and condensating. The cooler air at night is circulated through the pipes which picks up heat stored in the thermal mass of the soil. The temperature is thereby regulated day and night- the re-circulated air has a cooling effect during the daytime preventing overheating of the glasshouse and a warming effect at night.
 I don't have a science background and I must say this is blowing my mind. The technology and research began in America and one of the leading proponents there describes it as "The magic of phase change from liquid to vapor and back again"!
 Electricity is used to power the fans overhead but the amount used is minimal whereas traditional greenhouses use a considerable amount of energy to maintain optimum temperature.

 Martin is clear that the greenhouse is intended for sub-tropical growing as there simply isn't sufficient daylight in the UK that's strong enough for fully tropical plants. I expect he will push the boundaries to see what is possible but as well as being a polymath he is a very practical pragmatist.
 I will have to make this part one of several entries about the Littlehempston visit because there was a good deal more to see. To be continued...