I'm finding an awful lot of English texts and glossaries about wine that use the French term for this, and although some of them give an English translation there doesn't seem to be one generally accepted English equivalent: you get "literally 'in a crowd'", "huddled together", "randomly positioned", and various other things. But if the French term is well established in the English-speaking wine world, as many French terms are, and the context defines it, why bother with a translation at all? There's also a certain ambiguity about whether the main idea is randomly positioned or close together, and it would be convenient to avoid having to commit yourself on that.

A token English reference:

"Work was made more difficult by the system of planting en foule. Regional vigerons, like their counterparts in Burgundy and the Jura, continued to plant en foule until after the turn of the century. The term en foule derives from the disordered arrangement of the vines, likened to a "crowd" (foule) of people, but it eventually came to signify a "large number", because in this type of growing, the density of vines and shoots is much higher than with vines planted in rows"
https://books.google.es/books?id=Hu-mOnd9UqUC&pg=PT126&lpg=P...


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Note added at 4 days (2018-07-18 06:57:58 GMT) Post-grading
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Thank you, Victoria!