One of the great pleasures for me is getting together with friends and spend an afternoon distilling some freshly harvested aromatic plant species. This week I was fortunate to have two such days in a row.
At Stephen and Julies’ home near Laguna, there is a rosemary hedge that has a strong aroma of rosemary. That may come as no surprise, however rosemary comes with different chemotypes, some of which are not conducive to cooking with and using for medicine. For example the plants I have growing at home turned out to be CT camphor, while CT verbenone is popular among aromatherapists. But for flavour and medicinal use I prefer the 1,8 cineole type, which we distilled on this occasion. I made sure that I took some stem cuttings from non-flowering stems, to propagate them later at home.
The rosemary bushes were overdue for a prune, we helped provide a good trim, there were enough leaves to fill the 40 liter distillation pot. Fortunately we got started in the morning, it turned into a hot day. The leaves are stripped off the main stems and added to the distillation pot.
The pot sits on a three ring gas burner, and the condenser is kept cool by running water from a tank connected to a pressure pump. This water wasn’t wasted, it run down via a hose to some young cypress specimens that were looking a bit dry.
After a couple of hours and a delicious mushroom quiche lunch in between, we called a stop though less than one litre distillate had been collected. However there appeared to be a decent amount of oil sitting on top, to be separated out from the hydrosol later.
In the end we made about 20mL of essential oil, along with the hydrosol. Typically the oil has a fresh aroma featuring the high notes. It will oxidise a little and should turn into a good quality rosemary oil in a month or two.
The following day I visited my friend Terry on his bush surrounded residence near Elderslie. I had in mind to distill the Melaleuca decora I had observed growing there, but decided there weren’t enough trees for harvesting. However nearby was a large stand of red-flowering bottlebrush, Callistemon linearis.
Some authorities, including the Queensland Herbarium, now place all Callistemons in the Melaleuca genus, in which case this species would be Melaleuca linearis. The NSW Herbarium has yet to adopt this switch so I’m keeping with the old familiar name – along with most native plant lovers I still refer to these as Callistemons.
It turned into another hot afternoon, and an hour or so of harvesting the rather prickly leaves left us rather thirsty. Fortunately we had a six-pack of Coopers Pale Ale on hand, which we imbibed while the still boiled away and distillate poured out copiously for a couple of hours. This turns out to be a low yielding species, and no appreciable amount of oil was separated in the aftermath. However we obtained plenty of hydrosol, which is useful for all kinds of household and cleaning uses, and Terry likes to heat it in an oil burner to keep the air pure indoors.
According to an authoritative text (Brophy, Craven & Doran, 2013), essential oil produced from this species contains over 60% cineole, along with terpenes such as pinene and limonene. Hence it is a Eucalyptus-style oil with notes of pine and lemon. Traces of these chemicals are retained in the hydrosol providing the characteristic aroma. According to the text yields are as low as 0.1% hence it is little surprise that we failed to obtain any under the circumstances. However we shared a most enjoyable afternoon, and our hydrosol stocks received a timely boost.
Brophy, Craven & Doran (2013). Melaleucas. Their Botany, Essential Oil and Uses. ACAIR, Canberra.