Araucaria bidwillii Hook.

Araucaria bidwillii is a fast-growing tree 30-50 m tall, with a diameter of 1.5 m, and a straight, undivided trunk often free of branches for two-thirds of the tree height and showing little taper in this part of the bole. The crown is normally symmetrical and dome shaped (parabolic), tending to change from a pointed to a flattened apex with age. The drooping branches are themselves unbranched, with the leaves clustered at the ends. As the lower branches die, dormant buds become active at the base of each branch and a secondary, dome-shaped crown may develop below the primary one. Bark is persistent over the trunk and branches, with thin scales up to 2.5 x 7.5 cm. The outer surface of the bark is rough, bumpy, dark brown to black, covered with prominent leaf scars, and the cut blaze is red, grading to orange. Juvenile leaves most commonly seen in double rows along the branchlets spirally arranged, venation not visible, glossy green, triangular in section, stiff; adult leaf shiny, tough, sharp-tipped, glossy green, discolorous, 2-6 cm long, 0.5-1 cm wide, spirally arranged but become two-ranked through twisting of the leaf bases. They are stalkless or very shortly petiolate, lanceolate. Male and female strobili are usually borne on the same tree. Males up to 20 cm long, produced at the ends of short, lateral branches and made up of numerous spirally arranged scales, each with a diamond-shaped, expanded summit covering about 12 pollen cells. Females borne on short lateral branches and ovoid, made up of numerous bracts with sharp projections on the outer end; each bract has an ovuliferous scale attached to the upper surface. Mature cones are ovoid to almost spherical, very large, with woody scales up to 15 cm broad, and upon maturing they turn from green to brown. Male cones up to 18 x 1 cm, upright near the ends of higher branches; female cones erect, remarkably large and heavy, up to 30 x 23 cm, weighing up to 5 kg each, bearing a single seed. Seeds joined to the cone scales, brown, pear-shaped or kite shaped, up to 6.5 x 3 cm. The name Araucaria is derived from Arauco, a province of southern Chile, and the native habitat of A. bidwillii. The common name is of aboriginal origin. Bunya pine has a silhouette that is unique among Australian trees, and its seeds are much larger than those of other conifers.

Araucarias generally begin to flower and fruit between the ages of 15 and 20 years. Male and female flowers are typically found on different parts of the same tree. Male flowers usually appear at the base of the crown in young trees and female flowers at the top. As the tree grows older, the male and female flowers move closer to each other. Bisexual flowers are also found. After pollination, the female flowers develop slowly; the cones mature in about 2 years. They disintegrate on the tree or fall to the ground and disintegrate. Seed quality varies annually; if sufficient pollen is available, seed quality is usually good. The seeds generally fall within the periphery of the crown. In Queensland it flowers from September to October and fruits occur in January to February. Seeds disperse as the fruits mature. Trees bear seeds in 1-2 year intervals.

Many of the soils where A. bidwillii occurs are Krasnozems or chocolate loams derived from basalt.

The species does well at lower altitudes with good rainfall. In Australia, bunya pine mainly occurs in southeastern Queensland, between Gympie and the Bunya Mountains northeast of Dalby. There are small occurrences in northern Queensland, on Mt Lewis and at Cunnbullen Falls. Up to 30 frosts may occur each winter, mists are frequent, and the climate is generally humid. This species grows on the ranges within about 160 km of the coast, occupying various topographic positions from moist valley floors at low altitudes to ridge tops and upper slopes at higher localities. A. bidwillii is normally found as an emergent over tropical rainforest (simple notophyll vine forest), often in association with hoop pine (Araucaria cunninghamii).

A. bidwillii is easily grown from seed. No pretreatment is required. Under suitable moisture and temperature conditions (20-30 deg. C), germination may begin about 10 days after sowing; it is delayed by cooler temperatures, sometimes taking up to 50 days. Seedlings are grown under high or low shade, and for both types of shade, seeds are sown during spring. Seeds are sown in drills (furrows) 7.5-10 cm deep. A few months after sowing, ‘tubers’ (fusiform radicles) are formed. The seedbeds are redug, the tubers are collected, and they are either planted directly into soil-filled tubes or stored until they are needed. Exposure to sunlight before planting breaks tuber dormancy, and the plants begin to grow. Almost every seed produces a tuber, which develops into a plant. With low shade, the seed is broadcast sown on well-prepared beds and covered with 1.8 cm of sawdust. The aim of both types of sowing is to have a stocking rate of 120-160 plants per square metre. Newly sown beds are given full overhead shade for several days. Shoots develop best when in 75% shade for the first several months and 50% shade for the next 3 months. Shading should be removed gradually to give full sunlight 2 weeks before potting. Full light is not admitted until nearly 1 year after sowing. When 75% of the seedlings are 22 cm tall, they are lifted carefully to avoid root damage and potted. Potting is done about 5 months before field planting. Potted seedlings should be given full shade. The shade should be removed to full sunlight a month before planting seedlings to the field, generally when they are 2 years old. Seedlings are very susceptible to frost.

Trees may coppice slightly from cut branches and stems, and they should be planted under full sunlight.

Araucaria seeds have short viability under atmospheric conditions and should be sown within a month of collection. To be stored for any amount of time, seeds must be partially dried; the acceptable safe drying level is 25-40% mc. At this mc, seeds can be stored for some time at 5 deg. C. They should be sown as soon as they are removed from cold storage as they rapidly lose viability. On average, there are about 70-77 seeds/kg.

Shade and shelter: A. bidwillii can be planted as a windbreak. Ornamental: Is planted in parks and roadsides as an ornamental.

Food: The raw or roasted seeds are an important item of the diet for some of the aborigines in Queensland. Timber: The wood is very much like that of Araucaria cunninghamii, pale pinkish in colour, even in texture, with faint growth rings, and with a density of 520 kg/cubic m. It is not susceptible to lyctus attack.