Identifying characteristics:
The Jack pine is a small, rather untidy-looking pine usually growing 30
to 35 feet tall. Young trees have a pyramidal shape, but older trees often
develop an open, misshapen crown, with lower branches that die and persist
on the tree. The unusually short, stiff, olive-green needles
(0.75 to 1.5 inches long) are in fascicles of 2, strongly diverging from
one another. The margins are minutely toothed and stomatal lines occur on
the surfaces. The conical, 1- to 3-inch-long, stalk-less cones
bend forward on the branches, becoming curved and asymmetrical. The apophyses
are light yellowish-brown on young cones, becoming weathered and grayish
on older trees. At maturity, prickles are absent from the umbos. Cones persist
on the tree for several years, often remaining tightly closed. Adapted to
survive forest fires in dry seasons, the cones slowly open at 140 degrees
F, releasing the seeds slowly, allowing the ashes to cool before dissemination.
Buds are ovoid, resinous and dark brown, with blunt tips. Bark on young trees is thin and reddish-brown
to gray, becoming dark brown and scaly. On old trees the bark is divided
into shallow furrows and scaly ridges of thick, close-pressed scales.
Similar species:
Ecology:
Distribution: This is the most northern pine and it is essentially
a Canadian and Great Lakes species. It is native from near the Arctic Circle
in Alaska south and east to the Great Lakes states and the northern New
England states.
Habitat: The Jack pine is one of the hardiest native trees in North America, growing from zone 2 to 6. It is found on flat or rolling sandy plains, rock outcrops, woodlands and savannas, where the climate offers mild to cool summers and very cold, snowy winters. This pine will grow in dry, sterile soils and needs full sun and free air movement. It is a pioneer species and invades recently burned, poor, sandy or logged areas. It has a slow to medium growth rate and does not tolerate limestone soils, preferring dry, sandy, acid soils. Trees grown in plantations are subject to root rot. Stems of young trees are often malformed due to eastern gall rust, and seedlings easily succumb to root rot and damping-off.
Uses:
Wood: Wood is moderately soft, moderately light, weak and
close-grained. It is used for pulp, general construction, poles, posts and
mine timbers.
Wildlife: This pine provides cover and food for many northern wildlife species. Seeds are eaten by white-footed mice, red squirrels and chipmunks; and birds like goldfinches, grackles and robins. Deer and hares browse the saplings and porcupines damage the trees when they feed on the bark.
Horticulture: Not an ornamental tree, the Jack pine is seldom used by landscapers. It is used in the north for windbreaks, shelterbelts and for reforestation of severely eroded sites. Although the Jack pine grows faster than most other conservation-planting pine species in Iowa, the fertile soils support more valuable, larger and more ornamental conifers.
