Hey Wolf,
Go ahead and put your plants in, they'll do quite well for some time with just plain water being fed to them as is proven by raising plants in a jar with nothing but water.
If you have any old filter material that you can remove from a working fish tank, throw that into your over flow tank and that will help get the bacteria growing. Go to Pet Smart or wherever you can buy about 10 inexpensive gold fish and throw them in your fish tank, feed them sparingly at first and don't worry about the temperature and you're off and running.
Good luck