Stevia can be quite temperamental. It can die in what seems like perfect conditions for no reason at all except to spite you. Its saving grace is that sometimes it only pretends to die and will resurrect - sometimes taking up to a year to make up its mind to do it - so if that happens to you, don't give up on it, but keep giving the occasional drink to an apparently dead plant! Certainly, it will die (or die right back) if you allow it to flower.

It's not a particularly fast grower, is very slow to get going in fact, and it doesn't spread. I've never, ever had any luck propagating from my plant, though I've tried many times, using seed I've collected and cuttings.

The plant is climatically suited to climates from temperate to sub-tropical where temperatures range between 21-43C, with an average of 24°C, but it will also grow in the tropics, where it prefers shade and will also grow in cold climates with winter protection. Plants in the ground have been noted to take minimal frosts. It's dormant in winter and often loses its leaves, even here in the subtropics, which shows that it's really happiest in warmer climates.

It likes regular water, but won't tolerate water-logged conditions.

It can be a gangly plant, so it's a good idea to stake it to begin with, or to plant several plants close together. Once it's older, it can stand up quite nicely.

In short - theoretically it should be an easy plant to grow, but in practice it presents quite a challenge.

More detail (the theory part of it!):

Propagate by seeds or by tip cuttings taken in summer, or root division in spring. Seeds are notoriously infertile and slow to germinate. Flowering usually occurs 54-104 days after transplanting. Plants in the ground have been noted to take minimal frosts. It is a somewhat temperamental plant and may be slow to grow at first. Even in ideal conditions, it is not uncommon for plants to die suddenly or to lose their leaves. As long as the roots are alive, the plant may regrow. Poor, loose, well drained soil is recommended. The plants need to be well-mulched so that surface feeder roots do not dry out. For gardeners in cold climates, it is recommended that plants be started in large pots so that the pot can be moved to a warm verandah in winter. In cold climates, the plant may go dormant to the ground. As stevia does not over-winter outdoors in freezing conditions, the roots are lifted in autumn and stored indoors in perlite or sand and then set outside again in spring. Stevia requires regular watering in dry periods but has poor tolerance to long waterlogging or to saline water or soils. In its natural habitat, the plant occurs naturally on acid soils of 4-5 pH but will grow well on soils up to 9 pH. Leaf yields can be increased with a moderate application of nitrogen, phosphorus and potassium fertilisers. Plants also respond well to liquid seaweed as a foliage spray applied fortnightly. As soon as the plant flowers, the leaf production slows down, so it is an advantage to nip off flower buds, to encourage further leaf development. If the plant is left to flower, the tip leaves take on a slightly bitter overtone. Plant will die if left go to flower, so it should be cut back repeatedly to prevent flowering.

oh,thanks for the detailed message.

i got a cutting, and i planted it in a pot, it was growing a little, then i overwatered it, it just died.

so i am thinking about buying a whole plant from the store. from what i read here, it seems that it is not that easy to take care of?

i was hoping that it will grow like mints, so it can save me the money of buying sugar. ;)

Here are many threads about Stevia and how its grown. Its done by simply typing in the word 'STEVIA' in the search window at the top or bottom of every thread subject page.

It is fairly easy to grow stevia. Daisy provided a lot of good info on it.
I planted some for the first time this year and they are doing fine. mine got to about 2 ft tall, branching out.
I learned that you have to stake them, wather more often when it is hot.
I have not seen them flower and grow seeds yet, but you can get more plants by cutting and rooting them.
I will find out if they will overwinter in my area (zone 8).
I will cover them with leaves and mulch to protect from occasional freezing temps.

But all in all, stevia is easy to grow. A planted them along side basils and other herbs.

I've found them to be very easy. No chance of them overwintering here, though.