You shouldn't have to fertilize. It's a weed! We use round-up regularly.

Sorry for that. Evidently you love the weed. It needs full sun all day, every day. No fertilizer will help it, if it doesn't have sun.
Suzi

I agree with desertdance, although it's not as bad a spreading weed as self-sowing ones. It can be managed though, but very hard to get rid of. So most problems with growing it come from over watering (poor drainage), or too much shade. Fertilisers don't make a lot of difference if those two aspects are okay. I was always told they do best if there's bare ground around the base of the plant baked in hot sun each day, even if the soil is a bit poor. So I don't think you'd notice much difference between those two.

look at this page for lots of good information:www.centraltexasgardening.info/bouginfo.htm