near Nyon and ive already seen about 3 different places that are "selbst bedeinung", as in you go there, pick your pumpkin and theres a box where you put the money, noone is even looking to see you put the correct amount, the swiss people just trust you will. Im sorry I dont know geneva, plus its a city so a little harder to grow pumpkins there than in the country side.
There is a farm just off the Divonne motorway exit that you can buy pumpkins (well you could last year) its down towards Coppet Mies about 700m from the motorway exit as you pass the Founex turn off on the RHS.
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Ferme Courtois
Route de la Branvaude 13
1290 Versoix
022 755 43 16
http://www.fermecourtois.ch/
Pumpkins, apples (15 varieties), flowers, and more.
Open Monday and Tuesday from 9h-12h and 13h30-18h
Friday from 9h-18h, Saturday from 9h-17h
Closed Wednesday and Thursday.