Do poison arrow clouds stack?

Quick and simple question: Does the damage from Poison Arrow poison clouds stack?

I was thinking I simply needed to reapply the poison arrow every few seconds to keep the target draining life.

If I shoot PA as fast as possible and get many clouds at the same place do they all deal damage to the enemies in their radius?

I hope they stack, but assume they do not. If they do then I certainly was playing my now dead 31HC ranger wrong...

they do not, using it again refreshes the effect

I could have sworn the poison effect stacks up to 5 times...

Short answer: No.

Long answer: No, but Poison Arrow does have the highest base damage out of the elemental arrow powers per shot (tied with fire Arrow), so spamming poison Arrow does cause great single target damage with an AoE suppression that will stay up and follow the victims around. Besides, it's fun seeing a room full of toxic gas. =P

nvm