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Species Spotlight: Quercus costaricensis Liebm.

By Francisco Garin Garcia | November 25, 2021

Plant Focus

Quercus costaricensis is a Central American oak belonging to the subgenus Quercus, section Lobatae. It is my favorite oak among the Central American species: the first oak from that region to be cultivated in The Iturraran Botanic Garden (northeast Spain) and also the hardiest. It can be grown in areas of Europe with a mild climate and abundant rainfall. During its early years in Iturraran, barely 2 m tall, it suffered the worst frost recorded here in the last 40 years, with temperatures dropping to -7 °C. It lost its top and all its leaves, but it recovered the following spring, showing no further damage in future years.

_{The upper surface of Quercus costaricensis leaves are covered with sparse pubescence}

In its native habitat, Quercus costaricensis is a large, evergreen tree, up to 40 m or more, with a straight, cylindrical trunk; the canopy is dense and rounded, the bark is thick, grayish, fissured, though quite smooth in young trees. The leaves are dark green, leathery, oblong to oblong-elliptical, 10–15 cm long and 4–7 cm wide, the blade bullate, the margin entire, revolute or wavy, the upper surface dark green with sparse pubescence along the veins, the underside lighter and densely covered with light brown pubescence when young, later glabrescent; 6–9 pairs of veins impressed above and very prominent below, branching before reaching the margin. Petiole thick, pubescent at first, later glabrescent, 0.2–1 cm long.

Leaf undersides — _{The leaf undersides are covered with dense, light brown pubescence when young © Roderick Cameron}

Male flowers are disposed on coffee-colored catkins 4–9 cm long; female flowers grouped in clusters at the end of twigs. Acorns ripen in the first year, borne singly or in pairs, on a short, thick stalk, cupule cup-shaped, 1–1.5 cm long and 2.5–3 cm wide, enclosing up to half the acorn, which is hemispherical, yellowish brown, 2–3.5 cm long and 2–4 cm in diameter.

The wood is hard, heavy, dark cream-colored, somewhat pinkish when exposed; it can present cracks and warps in the grain, and it is used in carpentry to make furniture and posts.

_{New growth on a tree by the Pan American Highway, San José Province, Costa Rica © Roderick Cameron}

This species is protected in most of its habitat. In parts of the Talamanca mountain range (Cordillera de Talamanca), the trees were so large when they were cut down, with huge trunk diameters compounded by the large buttresses reaching several meters up the base, that they were cut at a height of around 3 meters, leaving tall stumps that still stand there today. Currently the wood from these stumps is being used locally for construction.

Tree in Costa Rica — _{A mature tree in Parque Nacional Los Quetzales, Costa Rica, at 3,000 m elevation}

It is a high-elevation species, growing at 2,200 to 3,400 m, with between 1,000 and 4,000 mm of annual rainfall. It forms pure stands and is found in primary and secondary forests.

Acorn — _{A maturing acorn on a tree at Iturraran Botanical Garden, Spain}

Quercus costaricensis was described by Liebmann in 1854. C. H. Muller provides a good description of this species in his 1942 publication The Central American Species of Quercus. He classifies it as the only member of the Series Costaricenses Trel. and assigns to it two synonyms: Q. endresii and Q. costaricensis f. kuntzei (the second is in fact a synonym of Q. copeyensis, another Central American species, belonging to section Quercus). In his Series Irazuensis, Muller includes Q. irazuensis and the Mexican species Q. rysophylla, though he considers this to be doubtful. In fact, Q. irazuensis is another synonym of Q. costaricensis. The difference between the two is that the former has larger leaves, attenuated at both ends and with an acuminate apex. At the time of Muller’s publication, the fruits were unknown, but they are identical to those of Q. costaricensis. Quercus endresii is simply a form with longer leaves.

Quercus irazuensis leaves — _{Leaves of the form originally known as Quercus irazuensis. This was the first specimen of Q. costaricensis to be cultivated in Iturraran, planted in 1995, currently almost 20 m tall.}

Its distribution extends from the mountains of central Costa Rica southwards to the north of Panama. According to some sources (e.g. Plants of the World Online, Oak Names, Tropicos), it is to be found in Honduras, but this seems implausible, as it is not found in northern Costa Rica or Nicaragua. According to the IUCN Red List, the occurrences in Honduras¹ were cases of misidentification. A study² of Quercus species in the mountain forest of Uyuca in Zamorano, Honduras, does not include Q. costaricensis.

Quercus irazuensis leaf undersides — _{Leaf undersides on the form first described as Q. irazuensis, Iturraran Botanical Garden}

It is one of the Central American oaks that perform best in Iturraran: we have six specimens, sourced from Volcán Irazú and Cordillera de Talamanca, all in very good health and growing vigorously at a rate of over a meter per year.