Stevia is a natural sweetener that can be grown on the windowsill indoors or on the patio outside. 

Regarding any possible health concerns, in April 2010 Stevia was declared safe for use by The European Food Standards Agency (EFDA). The panel concluded that steviol glycosides covered by the proposed specifications are not carcinogenic or associated with any reproductive/development toxicity.

This product is used abroad as a natural sweetener but at present is not approved as a food in the UK.