That is a very good link Unrulyevil posted, I came across it some time ago and I've learned from it.
Shadowcat0789, it is possible to have a lush planted tank without CO2. There simply has to be a balance between the light (intensity and duration) and nutrients for the type of plants. If you have a look at the photos of both my aquaria, you will see what is possible with minimal lighting (1 watt per gallon, but it is full spectrum), no CO2, plain gravel substrate, and liquid fertilizer twice a week. Both these tanks have been running 9 months, and I have previously had similar-looking tanks for 10 years.
Once you've digested the info in that linked article, we are here to offer specific answers if you have questions.