The Oil and Fibre Plant Seed (Wales) Regulations 2004

8.  In the case of monoecious hemp, the number of plants of the crop species which are recognisable as obviously not being true to the variety shall not exceedE+W

(a)one per 30 square metres for the production of basic seed; and

(b)one per 10 square metres for the production of C1 and C2 seed.