I used to grow the plant and it was quite easy to do so - although, over here, it needed to be grown as an annual. The leaves can be used to sweeten drinks or in cooking but apart from just growing it for interest it's easier to buy the extract.
The extract (steviol glycoside) is used in many forms and some of them can leave a slight bitter aftertaste. Rebaudioside A (one of the extract versions) has the least aftertaste and most people find it doesn't have any aftertaste at all.
Some of the commercial Stevia based sweeteners contain artificial sweeteners as well so you need to read the labels if you intend buying it. It is now recommended for use by diabetics but you still need to read the labels.
Some countries had banned it because of spurious research results but most countries have, now, approved it's use as a sweetener. I think the U.S. approved it in 2008. Here in the UK it was banned (through the European Community Commission) in the early 2000's but has since been approved after it was shown that the research results (lodged by an 'artificial sweetener' company) did not conform to research directives. Some sceptical people accused the company that had lodged the results of doing so deliberately to get the product banned. I was involved, very much on the periphery, with looking into the allegations.
The report that I received said their results were not spurious (as some had alleged) but had, apparently, used a much stronger dosage than the acceptable amount, and on too small a range of rats (one breed instead of at least three). That breed was known to be particularly susceptible to reproductive ailments!
I have been using Stevia for decades, but import mine from the U.S. as virtually all the myriad of Stevia products available here now have other additives.
So, by all means grow the plant/herb and use the leaves, but it's easier to buy the product. Read the ingredients if you have a particular dislike of or allergy to an artificial sweetener.
