Local names:
English (South American oak,Colombian oak), Spanish (roble negro,roble blanco,roble amarillo,roble)
Quercus humboldtii is predominantly evergreen tree to 25 m and a diameter to 1 m with buttresses to 1 m. The bark red/grey or grey, fissured, breaking into squares and flaking. Leaves simple, alternate, lanceolate, 10-20 cm long, clustered at the end of the branches; lamina leathery and glabrous, apex acute, base cuneate, shiny green above, lighter green beneath. Flowers yellow, small, unisexual; inflorescence a raceme; male flowers numerous, feminine ones in a cupula, styles long. Fruit light brown, ovoid capsule (acorn) with leathery pericarp, 2-2.5 cm in diameter and 5-7 cm long, resting on a scaly cupule. Only one fruit per cupule is developed, inside of acorn shell woolly.
Ecology
It is light demanding and often dominates competing species. In Colombia it is associated with Hedyosmum huilense, Clethra fagifolia and Billia columbiana in mid-zone forest.
Native range
Colombia, Ecuador, Panama, Venezuela
Tree management
The seedlings and saplings must not be exposed to direct sunlight. Planting density should be about 380 trees/ha. Maximum commercial value is reached after 35 years, yielding 400 m3 of wood/ha.
The fruits should be collected directly from the tree or by shaking the branches, as fresh fruits will have better viability and are less susceptible to attack by arthropods, worms, birds and rodents. The seed has a very limited capacity of dispersal due to its large size. The seed storage behaviour is recalcitrant. The fresh fruits have a moisture content of about 21%. The seeds can be stored for about four months in a cold and dry place with good aeration. Storage at humidity above 12% may result in premature germination or deterioration. Good results have been achieved by storing the fruits in water at low temperatures or in humid sand, moss or sawdust and kept under observation for insect or fungal attacks. There are 210-250 seeds/kg.
It is light demanding and often dominates competing species. In Colombia it is associated with Hedyosmum huilense, Clethra fagifolia and Billia columbiana in mid-zone forest.
Propagation is usually by seeds, root suckers and cuttings. Seed sowing should be done immediately after the fruits have been washed, and the sowing beds irrigated. The seeds can be sown directly in beds, or better in large bags, 20 x 30 cm. Sowing depth should equal the diameter of the fruit and the sowing distance 5 x 5 cm. It is advisable to use soil taken from a natural oakwood forest. Germination lasts 60-65 days. The seedlings can be transplanted to the field when they reach a height of 60-80 cm. Vegetative propagation can be done from the bare roots, root suckers, root stocks or cuttings. It has a great capacity for coppicing and it is advisable to cut 30-35 cm from the ground to obtain good shoots. A tree with a small diameter can produce as many shoots as a large one but the shooting capacity is lost when the tree reaches a diameter of more than 50 cm. Natural regeneration is prolific when there is a layer of moist humus on the forest floor. They develop in total shade satisfactorily, but later, due to lack of light and the competition with the smaller vegetation, a great number of them die.
In the mid-Andean montane region of Colombia, reforestation programmes use the native species for revegetation such as Quercus humboldtii, Billia columbiana, Alnus acuminata and Beilschmiedia sulcata.
The acorns are nutritious but, unlike the white oaks, are bitter. They serve as an important food for wildlife. If it is to be used as human food, then the acorns should be boiled repeatedly to get rid of the bitterness as the natives Americans did.
It produces good firewood and charcoal.
Timber: The wood is hard and heavy, easy to work, with a smooth finish. Wood density is 0.9-1.0 grams/cm³. Suitable for poles, tool handles, rollers and exterior use in general.
Ornamental: It’s a good ornamental plant especially along the road.
Other services: Two Colombian parrot species (Hapalopsittaca amazonia and Hapalopsittaca fuertesi) endemic to the threatened montane ecosystems of the Colombian Andes and particularly dependant on Oak (Quercus humboldtii) as a home.