Sap green

I’ve been neglecting the blog, because I’ve been insanely busy with getting my portfolio together, building my site, etc. But I’ve been experimenting with this and that as I’ve had time. Some of my recent adventures: an anthocyanin blue from geranium blossoms; an iron weld lake; shopping for a dragon’s blood tree; studying carmine in the wild; the first really successful madder lake from my garden plants (and figuring out how to make a dark and a light madder lake from the same batch); and the finding and purchasing of a natural-lake oil paint, from a very mainstream company, that has been out of circulation for most of a decade. I’ll share all that stuff with you, but for today I’ve prepared an article about sap green:

Sap green is a traditional color that enjoyed popularity from medieval illumination all the way through the Romantic era of watercolor painting. It is a warm, yellowish green, transparent, tending toward olive in masstone and a brighter, livelier green in tints. As an artist’s color it has been quite useful to many artists, filling in a difficult mixing area of the color wheel, supplying beautiful and interesting transparent green shadows, and lovely mixtures for foliage. It is fugitive, of course, like most natural organic colors, which is why it fell from vogue in the nineteenth and twentieth centuries, when modern synthetic greens that were more lightfast became widely available.

The color sap green is derived from the berries of the buckthorn plant. The usual plant used was rhamnus cathartica, or common buckthorn, which is found in the British Isles. The cathartica part of the species name refers to the fact that the buckthorn berries can be used as an emetic, and the plant is often mentioned in older medicinal treatises.

Sap Green - © MFA Boston

The dyestuff in Northern Europe is common and economical, and yields a beautiful color – small wonder it was popular for so long. The plant has been naturalized in parts of North America, and has become quite a problem in those areas, because common buckthorn can be very invasive. It spreads rapidly and aggressively, has no natural enemies on this continent, and quickly takes over an area of woodland, squeezing out the natural flora, and in the process some of the natural fauna as well, as they lose their traditional food sources to the invader. My original excitement to try growing this plant was dampened considerably upon learning of the problems associated with it.

I’m quite a fanatic about natural colors, of course; so, while I am an adamantly against risking introducing an invasive species into the ecolocality in which I live, I nevertheless spent some time in negotiations with myself. The common buckthorn is invasive in much cooler and wetter areas than southern Californa; there is little way the plant could be as successful here. In any case, the plant reproduces sexually and needs both a male and a female plant to spread; I’ll just get one plant, I reasoned, and so I’ll be safe. But in the end, I decided sadly that it just wasn’t worth the risks. I want to grow plants that can have a future in my garden and others – common buckthorn clearly doesn’t fit the mold, at least not on this continent. (The closest thing I have to an invasive species is madder, which is spreads agressively through root runners. But madder I feel confident I can control by killing it off if necessary, mainly because the birds and other animals of the area are not interested in its berries or seeds, so the chances of it spreading without my knowledge are greatly reduced. Common buckthorn does not have that element of safety; its berries are enjoyed and spread by many varieties of bird.)

If you happen to live in an area that has been invaded by common buckthorn, you have every opportunity to make some real sap green; for goodness sake go out and pick some berries. Every berry you use is one that cannot spread the species further.

There is another, non-invasive species of buckthorn that is actually much better suited for the hot and dry weather of California, being from the Mediterranean area of the Old World: rhamnus infectoria (or rhamnus saxatilis), the same buckthorn that is used to make stil de grain yellow lake. While a green can be made from the berries of this plant (depending on how ripe they are), it is much better used as a source of the lovely yellow stil-de-grain. You can get the berries from dye shops. I’ve been thinking of getting some seeds and growing a shrub in my garden plot; unfortunately, they seem a bit difficult to come by.

This is one of several posts I’ll make concerning the importance of localism in thinking about the sustainability of artist’s colors. If I lived in Northern Europe, sap green would be a primary color on my watercolor palette. Here in the American Southwest, it can’t be.

Tags: dye garden, lake pigments, natural pigments, sap green, sustainability