Pine family (Pinaceae)
Description: This coniferous tree is 30-70' tall at maturity. The growth and development of individual trees will depend on their situation. Trees growing in the open usually have a globoid-ovoid crown with a branching and crooked trunk, while trees growing in dense pine forests usually have a small oblongoid crown on top of a tall straight trunk. Branches within the crown are ascending-spreading to drooping; they are often crooked. Trunk bark is gray with reddish brown patches, somewhat scaly and flaky, and becoming slightly ridged with age. Bark of the branches is predominately gray or gray-brown and smooth to very flaky. Young branchlets are greenish yellow and smooth. The needle-like evergreen leaves are arranged on the branchlets in clusters of 2; they are pale green and ¾–1½" long. Each pair of leaves are divergent; individual leaves are slightly curved and twisted.
Jack Pine is monoecious with both male (pollen-bearing) and female (seed-bearing) cones on the same tree. These cones develop in small clusters near the tips of branchlets. The male cones are about ½" long and cylindrical in shape. After shedding their pollen, they soon wither away. The female cones are 1½–2" long at maturity, broadly lanceoloid in shape, and nearly sessile. These cones often turn slightly inward toward their tips. Initially, the female cones are mostly green, but they become brown at maturity during their 2nd year. The woody scales of the female cones are thickened toward their tips and without prickles (or they have very small vestigial prickles). The blooming period occurs during the spring or early summer for about 2 weeks. The cones are cross-pollinated by the wind. At the base of each scale of the female cones, there are 2 seeds that are winged and flattened. Individual seeds are 4-5 mm. long and their winged extensions are 10-12 mm. long. There are two types of female cones: Serotinous cones don't release their seeds until they have been exposed to the heat of a fire, while non-serotinous cones release their seeds immediately at maturity. If there is no fire, serotinous cones will release their seeds after a period of several years. The proportion of serotinous versus non-serotinous cones varies with the local ecotype. When the seeds are released, the female cones become globoid in shape, changing color from brown to gray. This tree reproduces by reseeding itself. Sometimes it forms dense colonies, particularly in the northern portion of its range.
Cultivation: Jack Pine prefers full sunlight, dry conditions, and an acidic mineral-rich soil that is sandy or rocky. Young trees start to produce cones after only 4-5 years. This tree is very winter-hardy. It is vulnerable to various disease organisms.
Range & Habitat: The native Jack Pine is found only in northern Illinois, where it is rare (see Distribution Map) and state-listed as 'endangered.' Illinois lies along the southern boundary of its distribution. Further to the north into Canada, this tree is common in some areas. In Illinois, habitats include sandy woodlands, sandy savannas, sand prairies, rocky sandstone cliffs, and stabilized sand dunes along Lake Michigan. This tree thrives in barren dry areas where there is a history of fire. While individual trees are only moderately resistant to fire, their seeds germinate in response to the heat and greater amounts of sunlight. Jack Pine is rarely used as a landscape tree.
Faunal Associations: Many insects feed on Jack Pine and other pines, particularly moth caterpillars (see Moth Table) and the larvae of long-horned beetles (see Long-Horned Beetle Table). Other insect feeders include the shield bug Tetyra bipunctatus, the Jack Pine Resin Midge (Cecidomyia resinicola), the Pine Spittlebug (Aphrophora cribatus), Pine Needle Scale (Chionaspis pinifoliae), the plant bugs Deraeocoris albigulus and Phytocoris angustifrons, the larvae of several sawflies (Diprion similis, Neodiprion lecontei, Neodiprion sertifera), the bark beetles Dendroctonus valens and Ips pini, the weevils Cimberis elongatus and Dryophthorus americana, the Pinetree Spur-throated Grasshopper (Melanoplus punctulatus), and the caterpillars of a butterfly, the Pine Elfin (Callophrys niphon). Pine seeds are eaten by both upland gamebirds and some songbirds (see Bird Table); they are also eaten by the Red Squirrel and White-Footed Mouse. White-Tailed Deer browse on the foliage and twigs of pines, particularly during the winter, while the Cottontail Rabbit browses on young seedlings and gnaws on the bark of saplings. Because of its dense evergreen leaves, Jack Pine provides good nesting and roosting habitat for many species of birds. An endangered bird species that is found in Michigan, Kirtland's Warbler (Dendroica kirtlandi), nests at the base of Jack Pine, where it is the dominant tree in sandy savannas.
Photographic Location: A foredune along Lake Michigan at Indiana Dunes State Park in NW Indiana.
Comments: This small tree is distinguished by its short needle-like leaves (only ¾–1½" long) that are arranged in clusters of 2, and its persistent pine cones, which have incurving tips and lack significant prickles. Other Pinus spp. (Pines) in Illinois have longer leaves (exceeding 1½"); some species in this genus also have their leaves arranged in clusters of 3-5, while other species have cones with significant prickles. Jack Pine's irregular pattern of growth often provides it with a 'bonsai' appearance.