Many years ago when I had a big garden, I found growing peas great for everything: the soil, whatever they were growing with, and even the kids when they were young & wouldn't eat anything green (they'd eat peas, pod & all & love them!)
Reading the Roses Love Garlic book (I hope that's what it's called but I'm an old woman so please forgive me!) changed my gardening life.
Here on the patio I find that my roses love herbs, the tomatoes love cilantro, & everything loves chives! I've planted herbs in pretty much every pot & they seem to make everything grow better plus they keep the soil moist, an important attribute here in the hot dry desert of Southern California!
I just found marigolds in the local garden center this week & I've squeezed them in w roses & tomatoes too.