Citronella oil takes months — and a distillation setup

Probably never, if you’re hoping to DIY it.

A citronella plant (the grassy kind, Cymbopogon — not the scented geranium sold at garden centers) needs about 3–4 months of growth before the leaves are mature enough to contain usable oil. But “usable” is doing a lot of work here.

The oil is locked inside the leaf cells, and you can’t just squeeze or chop it out. You need steam distillation — a real setup. Crushing the leaves gives you a faint smell, not an oil you can use in a spray or candle. The yield is tiny, too: about 1–2% of the leaf weight. So a full plant might give you a few milliliters of oil after hours of work.

If you just want the plant to repel mosquitoes by existing near your patio, it works fine (though the effect is mild). If you want actual citronella oil for making products, buy it from a supplier. Growing your own for oil extraction is a hobby project, not a practical source.