But locals, long spoiled with abundant parks and empty lots, are fighting tooth and nail to preserve their green oases. In 2014, voters blocked the construction of new housing on the giant site of decommissioned airport Tempelhof, which has been reclaimed by Berliners as a park.

The gardeners of Oeynhausen aim to take a lesson from that victory, commissioning expert reports, lobbying politicians and even calling a public referendum last year which saw an overwhelming majority support the preservation of the allotments.

"These kinds of conflicts are going to be more and more common in Berlin," warned Stefan Grundei, of the Federal Association of German Garden Friends (BDG), pointing to Berlin's dismal public finances and the brisk demand for property.

With 67,000 parcels of property, Berlin has more community gardens than any other German city - in part a legacy of the Cold War when a lot of land, particularly near the Wall, was relatively cheap and West Berlin was largely cut off from the East German countryside.

But "it seems that number will drop," Grundei says. An entire colony near the upscale shopping avenue Kurfuerstendamm was razed in 2010 to make way for luxury lofts.

Some regions of Germany have trouble finding enough gardeners for their allotments but in Berlin, years-long waiting lists are the rule.

Among the tiny tracts, usually leased in perpetuity, just over five percent change hands each year. Previous tenants can ask for thousands of euros (dollars) from those who succeed them to cover the cost of sheds, planted trees and garden equipment.

The rent for the plots of land themselves average about one euro a day, according to Thomas Wagner of the BDG.

"Access to green space should not just be for the elite but for everybody," he said.

The average age of a hobby gardener is 60 and the allotments tend to have an image as fusty redoubts for fastidious retirees. But young families who want to teach their children about nature are increasingly getting in on the act.

Holger Jost said he acquired his plot nine years ago for his vegetarian son, a fussy eater. His child is now grown but Jost still enjoys his 300 square metres of nature.

With a hat shielding his eyes from the sun, Alban Becker, president of the Oeynhausen association, says the garden puts him at ease, and his now-retired wife often nipped by to unwind after a stressful day at the office.

Becker says the plots are more than a perk for the lucky tenants but a green lung for "all of Berlin", including the robins, rabbits and foxes who flit through on hot summer evenings.

A crucial part of the battle for the survival of the garden allotments is conveying the message that they "contribute something positive for all of society", Grundei adds.

At Oeynhausen, large pathways are open to joggers and walkers from outside, a cafe serves al fresco lunches and information boards tell children about the secrets of flora and fauna. Leftover fruits and vegetables are placed in baskets, ripe for the taking for any passer-by.