root bound container bamboo

Help.
I started bamboo (gold green stripe, I think) in the largest container I could find at Lowe's. It has taken off but I think it may be root bound. The leaves get all shrivelled if we don't get rain once or twice a day. I've added more dirt on top, but it seems to be just a mass of roots. And my theory is that it dries out so fast because there isn't enough dirt. What do I do? I know bamboo is grown in containers all the time, but how do I deal with this problem. Also the leaves seem to be yellowing even though I fertilize with Miracle Gro every couple of weeks. I've also used OsmoCote.
Any suggestions?
Thanks.

I don't know enough about bamboos but in doing some research for myself, came across this informational supplement that may be helpful to you. You can scroll down and click through each section or click to any section from the menu on the left:
http://www.bamboosourcery.com/cat_frame.cfm

Repot it into a larger container, or plant it in the ground. Next rooting pot, make sure you have lots or organic material.
I grow roses in the same large pots and dump approx 2 cups or rich compost on top and try to wash it in. Best not to bury plants deeper than originally grown.

Mahalo for your suggestions.

Hi,
I work with a lot of Bamboo. Generally I try to use a third well broken down compost and then use seasoned manure pretty generously. When you repotting, I think of replanting a tree rather than most any other type of plant. I sometimes have repotted plants into a ground recessed rubbermaid trash can with the base removed. They are busy and need space for root growth(they love slow release nitrogen). I generally use fish emulsion to feed them until the plants are stable and actively growing. Some types will have prolonged dormant periods before visible growth. -The runners are generally establishing a network system for the next growth phase.
They also should not be allowed to dry out completely for the first six to nine months. Most types will show you with the leaves...if they need water or something more. As an overall health indicator look at the growth tips as much as the leaves. Solid fat buds are a really good sign of progressive growth even if the leaves have been distressed and even shed some.
Your gold green stripe may reach 30 ft depending on conditions, variety and how happy it is.
Enjoy...