How Lemon Eucalyptus Oil Is Made, From Leaf to Bottle

Lemon eucalyptus oil has no lemon in it and is not pressed from anything. It is the airy, scented part of a leaf, lifted off by steam, cooled back into liquid and skimmed from the water it floats on. Our oil is listed as a steam-distilled leaf oil of Corymbia citriodora, the lemon-scented gum, and what follows is how that process works in general.

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The tree sets the ceiling

A still can only carry out what the leaf holds. The lemon-scented gum is native to Australia (Queensland, in the case of our species) and is now grown in many other parts of the world. In their review of the species, Goodine and Oelgemoeller note that the composition of its oils varies with location, harvesting season and the age of the leaves. In other words, the character of a lemon eucalyptus oil is largely decided before a single leaf goes near the still.

The range is wide. A 2021 review by Southwell tabulates oil yields from 0.5 to 4.2 percent of the leaf for this species, with citronellal, the molecule behind the lemon note, making up roughly 65 to 85 percent of the oil. Our own aroma is "lemony, fresh and green" with a crisp, lightly camphorous base, which is the kind of profile a citronellal-rich oil gives.

What steam actually does

The idea behind steam distillation is neat. Steam passes through the plant material and sweeps the volatile aroma compounds along with it. Those compounds come over at close to 100 °C, well below the temperatures at which they would boil on their own. The compounds do not need to dissolve in water, only to have a meaningful vapor pressure at the steam's temperature. Once the mixed vapor is cooled, oil and water separate into two layers, and the oil is collected.

The Wikipedia entry on steam distillation adds that the conditions are fairly vigorous, around 100 °C for hours, and names supercritical carbon dioxide extraction as a gentler alternative for delicate compounds. We read that as a reminder that distillation is a craft of trade-offs. The heat and time that carry the oil out can also shape it, which is a good reason why two producers working with the same leaf can end up with slightly different oils. That is our reasoning, not something the entry states.

The equipment, in the order the vapor meets it

The charge. Leaves and fine twigs are loaded into the still.
The steam. In true steam distillation, steam from a boiler rises through the plant material. In water distillation, the leaf sits in boiling water. Laboratory studies often use the latter, so their yields describe that method, not a commercial steam still.
The condenser. The vapor is cooled back into liquid.
The separator. The condensate runs into a vessel where the oil and water part ways. The classic design is the Florentine flask: an oil lighter than water forms a layer on top, and the scented water underneath, called herbal distillate, can be returned to the still or kept. Small droplets of oil can leave with the water, so several flasks in series can raise the yield.

A leaf you can smell

If you ever meet a lemon-scented gum in a garden or a park, crush one leaf between your fingers. You get a lemony, green smell right on your skin, and it is an easy way to see why people plant the tree. The oil in a bottle is that moment in concentrated form, which is a nice thing to keep in mind when you read about stills and condensers.

Some arithmetic to put a bottle in perspective

Take Southwell's yield range. At 0.5 percent, a tonne of leaf gives about 5 kg of oil; at 4.2 percent, about 42 kg. That is our arithmetic, and it shows why leaf quality, harvest timing and handling matter so much. A bottle of oil is a concentrate of a lot of leaf, and the spread in how much each tonne yields is part of why oils of the same name can differ.

At a small, clean, modern distillery in Brazil with bright white walls

Why the first sniff deserves a little patience

A distilled oil is strong, and the nose tires quickly. Hold the bottle a little below your nose rather than right under it, and breathe in gently. Let the lemon arrive, then the green, then the dry, lightly camphorous edge underneath. Come back after a minute. You may find the second sniff tells you more than the first.

We like knowing how an oil is made, because it makes us better at explaining it. That is why this page describes distillation in general terms and keeps to what our listing says about our own oil: steam distilled, from the leaf, sold neat.

What this means when you choose an oil

It helps to know what to ask any supplier. Good questions are the botanical name, the plant part, the method, and whether batch documentation such as a Certificate of Analysis or GC-MS report is available. We list our oil as a steam-distilled leaf oil of the lemon-scented gum, sold neat, and if you need batch documentation for your formulation, ask us in writing through the contact page before you order. You may also enjoy our look at citronellal, the molecule that gives lemon eucalyptus its note and the story of the Australian tree itself.

Knowing how the oil gets from a gum tree to a bottle makes the first sniff more interesting. It really is a leaf, a little steam and a lot of patience.