Two genera of plants are included in this family - the Poplars
(Populus) and Willows (Salix). All species in this family are either shrubs
or trees with alternate leaves, small greenish to yellowish flowers
borne in catkins with staminate and pistillate catkins on separate
plants with the fruit a capsule and with seeds having a tuft of hairs.
While the two genera are quite distinct in general character and are
readily distinguished by the novice, the differences between the various
species of willows are not always so well defined and their
identification is sometimes quite difficult.
The following key points out the significant differences between the
various species included in this family. Those species which attain tree
stature in this park, marked thus (*), will be described more fully in a
later issue of "Nature Notes" which will deal specifically with the
forests of Mount Rainier National Park.
| 1.Leaves broadly ovate, acute
and finely toothed, with long petioles; buds with several scales and
resinous; a tree of the lower elevations, generally in moist places
along streams | ... Black Cottonwood (Populus
trichocarpa). |
| 1.Leaves usually narrow, short
petioled; buds with but one scale and not resinous; small trees to
prostrate shrubs | ... 2. |
2.Low prostrate
alpine shrubs only a few inches high | ...
3. |
2.Erect shrubs or
small trees | ... 4. |
| 3.Leaves lanceolate, acute at
each end, deep glossy green on both sides, about 1/2 inch long and with
prominent veins | ... Cascade Willow (Salix
cascadensis). |
| 3.Leaves oval, obtuse at apex;
green and shiny above but lighter below; underside of leaves greyish and
"powdery"; less than 1/2 inch long; strongly not veined beneath. A very
dwarfed shrub above timberline . . Arctic-alpine Willow (S.
nivalis). |
4.Species most
characteristic of sub-alpine zones - from about 4000-6000
feet | ... 5. |
4.Species more
characteristic of lower elevations - from about 2000-5000
feet | ... 7. |
| 5.Leaves "powdery-like" on
underside but not hairy | ... 6. |
| 5.Leaves with thin layer of
dense silky matted hairs on both sides when young (with age leaves
nearly free of these hairs); green on both sides; margins entire or
nearly so. Grows 3-9 feet high; leaves generally oblanceolate in
outline, 1-1/2 - 3 inches long. One of the most common willows in the
Hudsonian meadows in moist situations | ... Upland Willow (Salix
commutata). |
6.Leaves variable
in outline - ovate-lanceolate to obovate, rounded at base and cuspidate
at apex; 2-4 inches long, hairy above, especially along veins; margins
of leaves with numerous rounded teeth to nearly entire. A shrub from
3-12 feet tall; fairly common in Hudsonian meadows in moist
situations | ... Barclay Willow (Salix
barclayi). |
6.Leaves lanceolate
or ovate-lanceolate, rounded to cordate at base, 2-4 inches long,
glabrous to "powdery appearing" on underside, margins slightly saw
edged. A tall shrub or small tree, 6-15 feet tall; not
common | ... Mackenzie Willow (Salix
mackenziana). |
| 7.Trees with longitudinally
rough furrowed bark on lower trunk at least; leaves lanceolate and taper
pointed, hairless and appearing as if covered with white powder on
underside, upper side dark green and hairless; young twigs hairless also
... Gland Willow (Salix lasiandra). |
| 7.Shrubs or small trees; bark
not furrowed; leaves hairy, sometimes "powdery" beneath young twigs
hairy | ... 8. |
8.Catkins appearing
before leaves; leaves varying in outline but usually broadly
oblanceolate, margin entire or with small rounded teeth; dull green
above and paler below with either a "powdery" appearance or slightly
hairy on the underside but never with a dense matted silky sheen of fine
hairs | ... Black Willow (Salix
scouleriana). |
8.Catkins appearing
with the leaves | ... 9. |
| 9.Leaves on underside with a
densely matted silky sheen of hairs; leaves generally spatulate in
outline; 2-4 inches long; a tall shrub or small tree common along
streams | ... Sitka Willow (Salix
sitchensis). |
| 9.Leaves not matted on
underside with silky sheen of fine hairs | ... 10. |
10.Leaves dark
green and thinly hairy above, pale and powdery and silky below, entire
margin rolled back; leaves elliptic lanceolate to oblanceolate in
outline | ... Geyer Willow (Salix
geyeriana). |
10.Leaves dark
yellow-green on top and hairless, silver-white below with midveins
minutely hairy, margin of leaves not rolled back; leaves leathery, with
yellow stem and midveins | ... White Willow (Salix
lasiolipis). |
