Today's laboratory - Conifer identification

Oh, this is so much fun!  Most people, and my students are no exception, except for a couple of the horticulture students, commonly think several incorrect things about conifers.  1. All conifers are evergreen and that evergreen and conifer are synonyms.  2. All evergreen conifers are "pine" trees.  3. All evergreen conifers basically look alike.  4. "Furs" are Christmas trees and animal pelts.  So today TPP will endeavor to correct at least one of these misconceptions.  If you set your goals too high, you get disappointed.
In a few moments, once this cup of coffee and this blog are finished, TPP will grab his clippers and wander around our arboretum to obtain some nice specimens.  After you spend a few decades at this you get pretty good at it and you recognize most common genera by sight.  On one of our Botanical Geek Tours (locale Swathmore's campus arboretum) this one almost had TPP stumped, but then from somewhere, probably a mental process of elimination based on what it could not be, and this genus popped to the fore.  So here you go school kids.  Identify this conifer.
Unfortunately this genus doesn't grow here in the upper midwest, so my ID key to common conifers (including one  uncommon genus, which is in my garden so what the heck) won't be any help.  Don't say TPP has never given you anything.  It's an indented key, so hope the formatting works here (hmm, not quite).

IDENTIFICATION KEY TO LOCALLY-GROWN GENERA OF CONIFERS AND RELATED GYMNOSPERMS

 

1. Leaves small, scale-like, hugging the stem in pairs or threes. 

  2.  Scale leaves with glandular dot in center; leafy stems more or less flattened, leaves on two sides flat and on two sides folded or keeled. 

3.  Leafy branches flattened into 2-dimensional sprays, leaf keel convexly rounded such that apex points inward toward stem; cones oblong...............................Arbor-vitae (Thuja)

3'. Leafy branches not flattened into sprays, or only slightly so, leaf keel straight or concavely curved such that apex points upward along stem axis; cones globose  ……………… ………………………….………………………….. White cedar (Chamaecyparis)

  2'. Scale leaves without glandular dots; leafy stems rounded or 4 sided.

 

               3.  Leaves in pairs or threes, vestigial, fused into papery sheath around green stems with widely spaced nodes...........................................................Mormon Tea (Ephedra)

 

                             3’. Scale leaves small, but not vestigial, some leaves may be needle-like in whorls of 3 around

                                                stem; nodes closely spaced………………………...Red Cedar, Juniper (Juniperus)

  1'. Leaves linear, long and narrow, or broad and flat, borne on stems singly, in clusters or whorls.

4. Leaves borne in bundles of 2s, 3s, or 5s, needle-like, stout to long and flexible,..........Pine (Pinus)

4’. Leaves borne in helical whorls on short side shoots and at the ends of twigs.

5.  Whorls of flat strap-like leaves (greater than 3 inches long) borne at ends of elongate shoots, each leaf subtended by a bract ……………………………………Japanese Umbrella Pine (Scaidopitys)

5’.  Whorls of leaves borne on short, stubby, lateral branches (spur shoots); broad leaves or needle leaves (3-sided or flat and less than 3 inches long). 

6. Leaves stiff, sharp, 3-sided; cones erect on branches, 2-3” long, evergreen; not hardy in our  region ...............................................................................Cedar (Cedrus)

6'. Leaves soft, flat needles or broad, flat, fan-shaped; deciduous.

7. Spur shoots  less than 5 mm diam., leaf scars tiny, hard to see; Leaves long, flat, linear, soft and flexible; cones persistent, pendant or surrounding branch, oval, 1-1.5”; tree branches more or less at right angles to trunk …………….......…Larch (Larix)

7'. Spur shoots greater than 5 mm diam., leaf scars >2 mm wide; leaves broad and fan-shaped, no cones; tree branches angle upwards ………………….Ginkgo (Ginkgo)

                4”.  Leaves borne individually along stems (spur shoots absent), sometimes arranged or arrayed in 2 ranks.

8. Leaves on side shoots arranged in 2 ranks producing  feather-like lateral shoots; leaves all soft and flexible; leafy shoots deciduous.

9.  Leaves usually less than 1 cm long; leafy shoots (or scars) alternate on main stem …………………...........................................................................Bald Cypress (Taxodium)

9’. Leaves mostly greater than 1.5 cm long; leafy shoots (or scars) opposite on main stem.............................. ……………………………………….Dawn Redwood (Metasequoia)

8'. Leaves mostly spirally arranged (sometimes reoriented to present flattened array of leaves); leaves thick, leathery or stiff and needle-like; leafy shoots evergreen.

                                                10. Leaves 4-sided needles, very stiff..............................................Spruce (Picea)

                                                10'. Leaves flattened (cannot roll between fingers), linear.

                                                                11. Leaves narrow abruptly to short discrete stalks; foliage not aromatic.

12. Leaves with 2 white bands on lower surface; needles on top of twigs upside down, pointing to twig apex; small seed cones (1 cm long) …. ....................... ………………………………....Hemlock (Tsuga)

12'. Leaves all green on both sides (lighter below), stems showing segments at base of leaf stalks; ovules terminal on short shoots, seeds  with red aril at maturity…………...............................................Yew (Taxus)

                                                                11'. Leaves not on short stalks, but taper narrowing to base; foliage aromatic

13. Leaves narrowing to an elliptical base, raised from twig at lower edge; buds dry, conical .................................................Douglas Fir (Pseudotsuga)

13'. Leaves narrowing to a flat, circular base; buds coated in resin, dome shaped …………………......................….....................Fir (Abies)

 

Who invented the dichotomous key?

It's easy to take dichotomous keys for granted, and they are a wonderful tool for sorting through and calling your attention to significant details. After working your way through a complicated and detailed dichotomous key, and arriving successfully at an identification you get quite a feeling of achievement. One such key, Gleason and Cronquist's Manual of Vascular Plants of NE United States and adjacent Canada (NY Botanical Garden) puts a tremendous amount of taxonomic identification power in your hands (It is a bit hefty, so use 2), once you learn how to use it and get a bit of experience from a seasoned pro. In case you are unfamiliar with such devices, dichotomous keys offer you pared choices with each choice leading you to another pair of choices, and so on until an identification is reached. But who invented the idea? As best the Phactor can recall, someone said Jean Baptiste Lamarck, he of inheritance of acquired characters fame, had introduced the dichotomous key in Flora Francaise (1778), but seldom does that get mentioned as one of his scientific accomplishments. And now one of my colleagues (Lawrence Griffing) says that a botanist, Robert Waller, gave a talk to the Royal Society of London some 100 years earlier entitled: Tables of the English Herbs reduced to such an order, as to find the name of them by their external figures and shapes (27 March 1689). (The entire article may be behind a fire wall as it was just published, but us insiders can get the pdf file if anyone is truly interested.) This does not mean Lamarck got the idea from Waller, just that such a tabular approach was introduced earlier. Waller was very modern by linking his key to water color illustrations of the British flora and supposedly these illustrations are accessible online at the British Library (thus the origin of a previous post), but even after registering, the Phactor was unable to find the illustrations, or even get back in again, and not enough time to really fight with it. If anyone else is successful, do let us know.