Most of what a medicinal plant makes, it makes under pressure. Drought, flood, thin soil, insects, hard ultraviolet light — each stress prompts the plant to produce the substances that let it still reach seed. Those same substances are the ones that buffer stress in an animal body. Plants and animals grew up alongside each other, and the chemistry we borrow from them is the chemistry they built in order to survive.

Which is why timing decides everything. A plant’s chemistry shifts through the season and through the day, so what you draw out of a ferment depends on when you cut. Sometimes you get what you think you are getting, and sometimes you don’t.

Across four lectures Dennis works out the correspondence at the centre of this craft: the laboratory processes you use to draw medicine out of a plant are images of the processes the plant already used to make it. Germination through to seed is an analog of extraction.

Lecture 1 lays the ground — plant hormones and signalling substances, phenolics and flavonoids, and the alchemical pairs (gravity and levity, ash and oil, salt and sulfur) that let phytochemistry and traditional practice speak to one another without collapsing into DNA jargon.

Lecture 2 turns to fermentation: guiding a ferment through yeast and sugar, reading a hydrometer, knowing what is volatilising and when.

Lecture 3 goes into the glassware — building the equipment, the Vigreux fractionation column, Clevenger extraction of essential oils, the vinegar mother.

Lecture 4 closes on the influence of spiritual archetypes on matter, and on what separates a natural essential oil from a synthetic one.

Running through all four is the spagyric idea: taking apart what nature has fixed, purifying the parts on their own terms, and marrying them back together in rhythm. Nature is fixed in its rhythms. Humans are free to work with them.

You come away able to read what a plant is doing, and to build the apparatus that meets it.

Lecture 1 is available free as The Alchemy of Medicinal Plants.