The Science of Botanical Art

Conifers II

By Dick Rauh

Originally appeared in The Botanical Artist - Volume 17, Issue 2

 

For years I have thought of the two terms, gymnosperms and angiosperms, as equal and opposite. Their definitions – naked seeds and hidden seeds – appeared to support this, so I didn’t give it much thought. But from a taxonomic point of view (even though the terms themselves are no longer considered valid by some of the scientific community) they don’t match up.

Angiosperm is a synonym for the taxonomic division we call Magnoliophyta or Anthophyta, the flowering plants, but the term gymnosperm has no place in the accepted hierarchy. Instead it is a convenient grouping of four divisions that have the similar characteristic of having discovered seeds without yet learning the trick of enclosing them. These four divisions are Cycadophyta, Ginkgophyta, Gnetophyta and Pinophyta.

Now when we talk about taxonomy, you need to realize that there is a constantly shifting attitude about what belongs where, so I’m going to try a reasonable, more or less up-to-date approach and admit to possible conflict while ignoring it.

The division that comprises the conifers that we are interested in is Pinophyta, and  under that, the current thinking is a single order Pinales, and seven families. Except for some exotic horticultural species only three families, Pinaceae, Cupressaceae and Taxaceae, represent the native conifers we love to draw. Pinaceae, of course is the largest and includes, besides the pines (Pinus), firs (Abies), spruce (Picea), larch (Larix), hemlock (Tsuga), Douglas fir (Pseudotsuga) and cedar (Cedrus). Although there is no native true cedar species, the Cedar of Lebanon has been planted horticulturally in the Northeast and Pacific coast and you will find specimen trees  of this and other Cedrus species in botanic gardens and used ornamentally throughout the country.

This is true of examples of trees from the four more tropical or southern hemisphere families, Araucariaceae (the Norfolk Island Pine, which we treat as an indoor plant except for the deep South is in this family), Podocarpaceae, Sciadopityaceae, (the Umbrella Pine in this family is grown often as an ornamental) and  Cephalotaxaceae.

Of the seven genera in the family Pinaceae, the pines are the largest, with 14 species commonly regarded as natives with another group exclusive to the Pacific coast, including the Ponderosa pine, one of the tallest trees in the world. The needles of pines are grown in bunches or fascicles on short shoots. And except for the Sierra species Singleleaf Piñon, which has only one needle to a bunch (but is still a pine even though it might better be taken for a spruce or fir), our natives have two, three or five.

The Eastern White pine (Pinus strobus) is the only one with five needles to a fascicle. The shortest needles are found on the Jack pine (P. banksiana) around an inch long in clusters of two, and the longest on the Longleaf  pines, either P. palustris or australis, that can reach as long as 18 inches in groups of three. Larix and Cedrus also produce needles in clusters of many more than the pines, but the leaves are about the length of spruce and have a different look clustered around the twig. In the case of larch the needles are deciduous.

Pines are monoecious, bearing both the pollen producing cones and the ovuliferous cones on the same tree. The male cones appear in the spring, generally in small clusters at the terminal ends of branches, and tend to  be evanescent, disappearing after they have shed their pollen, often in smokelike clouds.

The male cones of the Table Mountain pine, P. pungens are a lovely purple shade, but most others are yellow-brown and quite inconspicuous until you look closely and find the interlocking spiral patterns of Fibonacci in their positioning on the twig.

As far as I can tell there is no defining position of the ‘female’ or ovuliferous cones in pines, they pretty much circle the stem, depending on how they arose, although they are mostly pointing down, especially the foot long cones of the sugar pine of the Pacific coast (P. lambertiana). Their upright cones, on the other hand, can define the firs, along with their habit of shedding the cone scales along with the seeds, leaving the erect spike of the receptacle as a remnant.

On the other hand the spruce seed cones always hang down, and unlike the pine cones are leathery rather than woody, and don’t have the distinctive umbo that is such a characteristic of the pines. The needles of spruce are four sided, rather stiff and sharp and leave projections on the twig that are distinctive and well worth  emphasizing if you were to paint a close-up of Picea. Fir needles on the other hand are flat and appear whitish on the underside like hemlock. The white are actually lines of stomata, the pores by which the cutinized leaves  are able to exchange gases. The twigs of Abies are smooth and the leaf scars round. Douglas Fir, which isn’t a fir at all but is in its own family, also has flat needles but these leave an oval leaf scar, are straight where the fir needles are curved, and are uniform around the twig.

Hemlock needles give the appearance of being two-ranked, even though they grow around the stem, and are  sparser than spruce, and darker in color, with a white underside.

The members of the Cupressaceae, juniper, arbor vitae and cypress are characterized by their scale-like foliage and this is a challenge all its own, the flattened interlocking scales producing patterns that are lovely in detail and to my knowledge rarely painted.

Yew branches are fuller than hemlock, the leaves two ranked, linear and flat with a tiny petiole and again a deep rich green in color. Instead of the cones of the other conifers Taxus have adapted their seed bearers into a red berry-like organ, which I suspect is why some scientists put them into their own order.

I see the approach of botanical artists to this group of plants in the depiction of the details of branch and  cones, and the ability to isolate the individual tree and illustrate its particular qualities. And here again we have a group of plants that will test your abilities to engage in a limited palette of greens and browns.

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  • Picea glauca, White Spruce, Graphite, (C) Nancy Gehrig
  • Pinus resinosa, Red Pine, Colored pencil, (C) Nancy Gehrig