Friday, September 25, 2015

Birches are outstanding!

Birches stand out due to their smooth, shiny, bark with long, dark horizontal lenticels,* that ranges in color from the striking white of Paper Birch, through River Birch's salmon pink, to the muted yellow-gray of Yellow Birch and charcoal-gray of Sweet Birch.  Paper birch and the similar but more darkly-marked Gray Birch are the ones that jump out at you.  These are the ones found in the 'burbs.  Of the two, gray birch is the local; paper birch is typically a tree of more northern forests, but often planted.  Paper birch is the "canoe birch" of the American Indians.  (Yes, there are still folks who make them.)  After first admiring River Birch in the South, I was surprised to find a couple in this neighborhood.  I've never encountered it wild.  The remaining two birches that occur in these parts are the yellow and the Sweet (whose sweetness you may have tasted in birch beer).  Though they're handsome trees in their own right, they are forest trees I haven't seen planted; look for them locally in Blue Hill Reservation.  

Beside the characteristic bark, birches are united by their fruits.  The green, sausage-shapped cone-like clusters ripen to brown, and then come apart into hundreds of tiny samaras (or nutlets) that whirl to the ground along with the fleur-de-li-shaped scales that bore them.  River Birch released its samaras to the wind way back in mid-June, but Gray and Paper Birches are just starting to do so now. 

River Birch (Betula nigra) can become a large tree.

 River birch (Betula nigra) has faintly pink, very shreddy bark and rounded leaves.

River birch in June: ready, set, go!
 June 5th

 River Birch fruit remaining in tree June 16th,
 and tiny, double-winged samaras and scales on ground on the19th.

 Gray birch (Betula populifolia) has more angular leaves than paper birch,
and the bark is marked by black chevrons where there were once branches.
(An unripe "cone" is visible among the leaves below center.)

Looking ripe by September 6th, some cones had begun dropping samaras by the 16th.
(The skinny green things are next year's flowering catkins.)

Gray birch cones on September 26th.  Samaras and scales fall, leaving behind the central axis.

 Paper Birch (Betula papyrifera), with its paper-white bark, has more rounded leaves than gray birch.
It also is  beginning to drop seeds.

Paper Birch (Betula papyrifera) cone scales look like fleur-de-lis, while the smaller samaras
are tiny oval seeds with two tiny round wings.   (Several "large" ones are right of center).

Yellow Birch (Betula allegheniensis) is common in the woods around Ponkapoag Pond.
The yellowish-gray bark shreds into strips so thin as to be translucent. 

The dark bark of Sweet Birch (Betula lenta) is a bit like that of cherry; it is smooth in a young trunk, 
but splits vertically rather than peeling as it grows.  (I don't know when these two trees set seed.)

Birches are sun-loving, relatively fast-growing trees, and gray birch in particular is short-lived.  If you want to grow a paper birch or gray birch of your own, find one of these striking trees overhanging a street or sidewalk.  The tiny samaras--almost like little fried eggs--collect in cracks in the pavement, or lodges among detritus.  Bag a few pinches of them and throw into the back of your refrigerator, or better yet keep them outside: they needs to experience enough cold weather to break their winter dormancy, then most should sprout next season. 

*Most trees with smooth bark develop rough, porous areas called lenticels that enable the living tissue beneath to breathe.  Their size and shape can aid in tree identification. 

No comments:

Post a Comment