There are no plants I can think of that will stand up to the traffic an allotment path carries - even a tough utility grass will turn into mush.

There are ways around this though... What about using paving slabs to make your path, but on top of the ground rather than flush with it, and with wider than usual gaps between them (say 30mm?). Then you could plant camomile or thyme between them, and it would grow to the level of the slabs.

Or, if you can find a cheap source, there are plastic 'hex grids' available for making areas of turf more hard wearing (they use them in some public gardens to keep the lawns looking good despite heavy traffic). You lay the grids flat on the ground and the grass grows inside them. Could work with herbs too maybe?

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Resistance is fertile