"Does it work?" - Not really :-)

Pelargonium 'citrosum' is marketed as "mosquito plant" or "citrosa geranium" in stores in the United States and Canada, even though research indicates the plant is ineffective against Aedes aegypti mosquitos."Not only was the plant ineffective at protecting humans against Aedes
mosquito bites, the mosquitoes were seen landing and resting on the
citrosa plant on a regular basis."

It is also NOT the source of citronella, which is derived from a type of lemongrass, Cymbopogon spp.

^ I don't trust everything Wikipedia say.

I don't know if it actually drive away mosquito, I think you need to grow one every square meter to keep them away.

I do put one of these plant next to a garden plants to help ward off pests, and so far my sunflower doesn't get attacked by leaf miners like it used to. I also put a lemongrass right next to my michelia alba, so far it seem pests leave the tree alone.

Uhhhmmmm.......if you were commenting about my post, Wikipedia actually took that info from another website. There are any number of pelargonium websites that state the same thing.