CHADAHS
... is the Central Hornsey and District Allotments and Horticultural Society - a society of local allotment holders (Shepherds Hill and Alexandra Palace) and gardeners.
All local gardeners in Haringey are also welcome to join the society.
CHADAHS say: "As a Society of enthusiastic and passionate gardeners we have a huge range of knowledge and skills from beginners to cup-winning experts, and each September we hold an Annual Show. Our Show is one of London’s best and liveliest with hundreds of entries from local allotment growers and gardeners."
Much more at the CHADAHS website.