Q: Is the citrosa plant effective against mosquitoes? Is it an annual or a perennial?
A: The citrosa is actually a scented geranium. Many plant oils are somewhat repellent to insects – lemon balm actually contains more citronellal oil than the citrosa does.
If you rub the plant leaves on your skin, insects will be kept away for a short time. One experimenter estimated plant oils to be 40 – 60 percent as effective as DEET (click for sources), the active ingredient in many mosquito repellents.
Personally, I use a different repellent: picaridin (click for sources). It does not have the oily feel of DEET products.
If you depend on the citrosa plant to keep mosquitoes away from your patio, you’ll be disappointed.
On the other hand, a pedestal-mounted oscillating fan works very well in my experience.
The citrosa is grown as an annual in Atlanta. It may be perennial in places where frost is rare.