How much essential oil do you actually get from lavender? We spent 48 hours at Rabbit Mountain Lavender Farm in Boulder, Colorado, harvesting and steam distilling an entire crop on professional equipment to find out. The short answer is that you can expect 30-70 milliliters of oil and 1-2 quarts of hydrosol for every 7-8 pounds of steam distilled lavender. In other words, more than 6-7 ml per pound of lavender on average. However, this number can vary widely based on a number of factors we discuss below.

Lavender Variety Matters More Than Anything Else

If yield is your goal, variety selection matters more than any other single factor. True English lavender smells sweeter but produces less oil. Lavandin hybrids like Grosso are what commercial growers plant, because they can produce two to three times the oil. High-yield varieties like Grosso and Riverina Thomas will dramatically outproduce varieties like Miss Katherine or Buena Vista. On this harvest we distilled Miss Katherine, Phenomenal, Maillette, and Empress Purple.

When to Harvest Lavender for Essential Oil

Cut lavender when the first flowers on the stem are opening. That's when oil content peaks. If you rub a stem and your hands come away sticky and fragrant, that's the oil, and that's what we're after.

A trick we use at the farm: let the bees tell you. Bees only visit flowers that have opened, so when a plant is alive with bees, it's nature telling you it's full of oil. We typically look for 25% to 50% of the blooms to be open at harvest. Go too early and the plant hasn't produced enough oil yet. Go too late and production starts falling off.

A few more harvest rules that make a real difference:

• Pick in the morning. Time of day affects oil content.
• Keep some green on the plant. On older plants the woody growth can reach surprisingly high up the stem. Cut into the wood and you'll likely kill the plant.
• Distill fresh. The faster the plant material goes from the field into the still, the more oil you keep.

One note on timing: in July, certain varieties will bloom a second time. The second flush is usually smaller than the first, and a mid-season harvest is a heavy pruning that can stress the plant, so we save the second cut for dried flowers rather than distillation.

Steam Distilling the Lavender

Steam distillation is how almost all real lavender essential oil is made, and the process is the same for peppermint, rosemary, eucalyptus, and pretty much any aromatic plant. We used our 240V essential oil steam distiller, a double-chamber system. The reason for two chambers is simple: water boils in one vessel and the plant material sits in the other. The plant never touches boiling water, so nothing scorches and nothing stews. Steam passes up through the lavender, ruptures the oil cells, and carries the oil out as vapor.

A few loading tips:

• Don't pack the plant material too dense. Steam has to move through everything. A false bottom in the plant chamber lets steam rise evenly through the material with no cold pockets.
• Load cold, pre-heat water to boiling temerature then hit it with full steam right away. This one is backed by research. Rather than letting the material slowly warm up, an immediate blast of full steam ruptures more oil cells and gives better extraction. It's also why a powerful heat source matters. We ran a 5,500 watt element on 240V with a digital touchscreen controller, which gets up to temperature extremely fast.
• If you're distilling outside, set up a pop-up tent. Rain and distillation don't mix.

Once steam hits the condenser it turns back into liquid and drips out as two products at once: lavender essential oil, which floats, and lavender hydrosol underneath.

How Long to Run the Still

We ran each 8 gallon batch of lavender for about 25 to 30 minutes. With a powerful still, that's plenty of time to extract essentially all of the oil the plants are going to give. You can run longer to collect more hydrosol, and some farms do exactly that, but we've found that collecting more dilutes potency. Since our goal is oil, we stop at 25 to 30 minutes and load a fresh batch.

Don't Throw Out the Hydrosol

If you've never heard of hydrosol, it's the distilled plant water, and it carries the scent and water-soluble properties of the plant. People use it as a linen spray, a room spray, a skin toner, and in aromatherapy. It used to be considered a byproduct, but it isn't. You get quarts of it free with every run, and if you've ever priced lavender hydrosol, you know it isn't cheap. Save it.

Separating the Oil

The oil floats on top of the hydrosol, so separation is just a matter of draining from the bottom. We use a glass separator with a stopcock. The hydrosol drains off the bottom (ours runs through flex tubing at a trickle into a glass carboy), leaving pure oil behind. No pipettes, no skimming, and no water left in your oil. That last part matters, because water in the oil is what makes it go bad on the shelf.

Measure Every Batch

We strongly recommend weighing your plant material and measuring your oil production on every single batch. It's the only way to dial in your process. We use a baby scale for the plant material and a kitchen scale for the oil.

One catch on measuring: scales that display milliliters assume you're weighing water. Essential oil is less dense than water, so multiply the scale's reading by 1.13 to get the true volume. Same if your scale reads grams: grams times 1.13 gives you the actual milliliters of oil.

To make the record-keeping easy, we built a free lavender yield calculator and tracker. Enter the data points above and it automatically converts your results into fluid ounces of oil per pound of lavender, saves every batch, and includes a notes field for anything worth remembering ("harvested right after a thunderstorm," for example). That way you can compare runs and figure out what's actually moving your yield.

The Honest Answer

It takes a lot of plant to make a little oil. That's why real lavender oil costs what it costs. But every drop of this is pure, and we know exactly what's in it. If you're growing lavender at home and wondering what to do with your harvest, this is, in our opinion, the best answer there is. Everything works the same at garden scale. Same process, same steam, just a smaller pile of flowers.

And it's not just lavender. Rosemary, peppermint, lemon balm, pine: if it smells good growing, you can distill it.