Oh, I forgot, even with a coleus, you'll need to change the water frequently to keep it from getting yucky.

Yeah i know its more easy in other mediums but want to try growing them roots in water.. I wonder if chloor will affect plant grow. Tap water is treated with chloor and borehole water is also available

The only way to prevent the water from going 'orrible, is to change the water regularly. It is the plant itself that is making the water go off.

Thanx why is the plant doing that to the water?

It's rotting.

What kinds of plants are you wanting to grow? Some wouldn't be good candidates for water rooting.

My suggestions are that you dip your freshly collected cuttings in a 10% bleach solution before placing in the water. You may also add a few drops of hydrogen peroxide to the water, too. Cover the jar in order to keep the water dark....less opportunity for algae to proliferate. And change the water frequently.

While the plant takes time to make the roots, you can change the water. Just don't let it sit so long that it becomes bad. It will look and smelly yucky and you'll be tempted to throw the whole thing away.

Discussing the particular plant in question would probably yield helpful info more readily than a theoretical, general discussion, especially if you're also interested in trying something other than the jar of water.