Note that I said “need.” While all the plants listed below are attractive, the reason they made this list is that they provide something extremely useful for your balcony or patio…
Scientists have determined that an essential oil in catnip attracts green lacewings. And green lacewings eat aphids like they are the tastiest thing on the planet. This makes catnip an awesome companion for roses and other aphid prone plants, not to mention folks growing many kinds of edibles that aphids love.
Another aphid eater, ladybugs, love dill. I know this from my own experience, because my dill plants were covered in ladybugs last year. Luckily science back me up. As that article explains, attracting native ladybugs is much better than buying them at the store because native ones tend to eat more than the varieties imported from various Californian mountain ranges (the collection/shipping process apparently disrupts their eating schedule).
Lemon balm in a natural mosquito repellant. Some varieties are up to 38% citronellal an essential oil that the pesky biting little suckers don’t like. Try Lemon Balm ‘Quedlinburger Niederliegende’ from Johnny’s Seeds, as it is full of the good stuff.
If you’re not too squeamish, comfrey is a great home to spiders, which in turn will eat a whole bunch of bugs that are unpleasant to have around, like flies. According to Organic Gardening Magazine, a square yard of comfrey can house 240 spiders! Granted you probably don’t need or have space for a square yard, but even one or two plants is bound to attract more than enough of the eight-legged fellows.