are you referring to liquid fertilizers? Might I suggest using those slow release fertilizer granules instead. It's available as the plants need them and no dangers of overwatering or root burns.

I second the slow release granules. Same thing I recommended for your petunias.

Ianna, is there a certain brand I should buy? I need to run to Walmart tomorrow so I'll pick some up.

I assume I just sprinkle it around the plants?

Both of these are made by Scott.

Miracle Gro Bloom Booster

Osmocote

Here is a link that might be useful: petunia thread

I don't go for any particular brands. It's just a safer way to use fertlizers. I use them more in my container plantings. For my flower beds, I like using a combination of composted manure and bonemeals and that's all.

Oh and if you do have a chance to fine Myke it's an excellent additive - helps the roots of plants absorb more nutrients.