Looks like you need to apply for a license to grow it.
Hemp is the common name for cannabis and the name most used (in English) when this annual herb is grown for non-drug purposes. These include the industrial purposes for which cultivation licences may be issued in the European Union (EU). When grown for industrial purposes hemp is called, often, industrial hemp, and a common product is fibre for use in a variety of different ways. Fuel is often a by-product of hemp cultivation.

Hemp may be grown also for food (the seed) but in the UK at least (and probably in other EU countries) cultivation licences are not available for this purpose. Within Defra (the UK's Department for the Environment, Food and the Rural Affairs) hemp is treated as purely a non-food crop, despite the fact that seed can and does appear on the UK market as a perfectly legal food product.

In the UK, at least, the seed and fibre have been always perfectly legal products. Cultivation for non drug purposes was however completely prohibited from 1928 until circa 1998, when Home Office industrial-purpose licences became available under the Misuse of Drugs Act 1971.
Legal issues of cannabis - Wikipedia, the free encyclopedia