Don't overdo the fertiliser, especially while the plants are babies. Overfeeding can kill any baby plant - even adults!

Either choose a slow-release general fertiliser according to manufactuer's instructions, or apply a liquid seaweed as a foliage spray once fortnightly.

For heaven's sake, don't allow the soil to become waterlogged - nor let it ever dry out completely. Watch the watering - it can be quite a thirsty plant, but doesn't like constantly wet feet.

Mine is at least 10 years old, maybe more. I remove flowers as they appear - I've found that if I leave the flowers on, the plant dies back to nothing. It always comes back, however.

It's a temperamental little beast and will sometimes die just to spite you. Don't give up on it, however - if you continue keeping the soil just barely moist, it might just resurrect - even up to a year later!

Oh! and don't fertilise plants in winter! Most plants go into dormancy or partial dormancy then.

As an alternative to commercial fertilisers, you can fertilise your plants with a handful or two of compost. It works really well with the stevia. Mine's in a pot, and I just do it whenever the soil level gets a bit low.