Gray Birch
Wire birch
Betula populifolia Marsh.
Bouleau gris

Leaves
Triangular, 4-7 cm long.
Tip long-pointed, tapering.
Base almost straight across, pendulous on slender stalk.
Upper surface rough, shiny dark green; lighter beneath.
6-9 veins per side, each ending in a large tooth
40 (18-47) teeth per side, distinctly of 2 sizes, larger ones sometimes appearing as small lobes.
Toothless near the stalk.
Preformed leaves hairless; neoformed leaves slightly hairy.

Buds
Pointed, uniformly light brownish-gray, gummy, often hairy.

Twigs
Slender, dark brown to gray, hairless.
Many resin glands.

Flowers
Pollen catkins usually solitary, about 2 cm long in winter, 6-10 cm at pollination.
Seed catkins 1-1.5 cm long.

Fruits
Mature seed catkins 1.5-2 cm long, narrow, blunt-tipped, semi-erect.
Nutlets almost hairless, wings much wider than the nutlet.
Scales 2-3 mm long, densely hairy on the inner side, with 2 broad recurved lateral lobes and a very short central lobe.
Shed in late autumn and early winter.

Bark
Thin, smooth, dark reddish-brown when young.
Becomes dull chalky-white, peeling with difficulty into small thin rectangular plates.
Triangular black patches often form below the branches, caused by a fungus (Pseudospiropes longipilus) growing on excretions from the bark.

Size and Form
Small trees, up to 12 m high, 15 cm in diameter, and 50 years old.
Often in clumps.
Trunk usually curved and leaning; distinct nearly to the top of the crown.
Crown narrow, irregular, open, with many slender branches; older branches often S-shaped.

Habitat
Occurs on sandy or gravelly soils of any moisture regime.
Found in pure stands on abandoned pastures and areas recently cut or burned.
Eventually replaced by more tolerant and longer-lived species.
Shade-intolerant.

Notes
Leaf-out occurs about a week after that of white birch.
Somatic chromosome number is 28.

Somatic refers to anything related to the body (as opposed to reproductive cells). In this case, it refers to the cells that make up the tree's body, excluding the reproductive cells like sperm or egg cells.
Somatic chromosome number refers to the total number of chromosomes found in the tree's body cells (somatic cells). This number is important because it tells us how many chromosomes the species has in its non-reproductive cells.
In most species, the number of chromosomes in somatic cells is diploid (two sets of chromosomes—one from each parent), but some species can have variations, such as polyploidy, where the number of chromosome sets is higher than two.
So, when we say the somatic chromosome number is 28 for Gray Birch, it means that in the body cells of that tree, there are 28 chromosomes.

Quick Recognition
Leaf triangular, with a long tip.
Bark dull chalky-white, not peeling readily, with black patches below the branches.
Branches thin, often S-shaped.
Seed catkin scales densely hairy on the inner side.