Log in

Editor's Picks

292539778_347822590870422_1318855334946924150_n.jpg
A single specimen found!
Website Editor | Aug 11, 2022
Quercus engelmannii seedling
Importing acorns for ex-situ conservation
Josephine Brennan | Aug 02, 2022
Quercus welshii on dunes site south of Kayenta, Ariz.
A threatened oak found in northern Arizona and southern...
Cindy Newlander | Jul 31, 2022

Plant Focus

Quercus tonduzii with acorn
An oak found only on a volcano in Costa Rica

The Barva Oak

Since 2012 I have traveled to Costa Rica four times, searching for acorns of some Quercus species that were not represented in the collection at Iturraran Botanical Garden.

One of the species I was keenest on was Quercus tonduzii, which has only been found on Volcán Poas, a volcano and national park about 45 km northeast of the capital San José. I have only ever found immature acorns. My last attempt, in 2017, coincided with a period of volcanic activity and access to the volcano was closed. So Q. tonduzii continues to elude me and remains at the top of my wish list.

During my visits to Volcán Poas, in the fields immediately below the National Park, I always noticed a Quercus with shiny leaves, more rounded than those of Q. copeyensis, similar in shape to Q. costaricensis. I never found acorns on these trees, so I am not able to determine what species they may be. I think they may be what Trelease named Q. costaricensis f. kuntzei. It was later renamed as Q. copeyensis, but I believe that it may be this oak I saw on Poas.

Quercus sp. in Sector Barva of Braulio Carrillo National Park
Quercus sp. in Sector Barva of Braulio Carrillo National Park

As I thought it strange that Q. tonduzii should only occur on Volcán Poas, I have searched for it in similar locations, mainly on Volcán Barva. This volcano is in Sector Barva of Braulio Carrillo National Park, about 20 km north of San José. The sector conserves an area of almost virgin forest made up principally of very old specimens of Q. copeyensis. Near the entrance one also finds Q. seemannii and some trees of an oak that at first I thought could be Q. tonduzii. Then I discarded that idea as the leaves were quite large, and Q. tonduzii has relatively small leaves. I had also found no acorns on this oak, and I thought it may be a variety of Q. copeyensis, or similar to the oaks on Volcán Poas.

Leaves and acorn cup of Quercus sp. on Volcán Barva
Leaves and acorn cup of Quercus sp. on Volcán Barva

This year, however, I was able to find acorns for the first time on some trees and I found that they are completely different to Q. copeyensis and have other characteristics that indicate this may be a new species, as yet undescribed, that has been confused with Q. copeyensis.

Several acorns germinated and I have seedlings growing in Iturraran. Hoping that someone may be able to study this tree in depth in the near future, the following is what I can say about it at this stage:

Description

Subgenus Quercus, Section Quercus.

Presumed distribution:
Verified to exist on the Cordillera Volcánica Central in Costa Rica, from Volcán Poas to Turrialba. Possibly also on the Cordillera de Talamanca.

Evergreen tree to 40 m or more.

Bark thick, greyish-red, deeply fissured with small plaques. Thick twigs, dark brown, covered with prominent white lenticels.

Detail of bark, deeply fissured with small plaques
Detail of bark, deeply fissured with small plaques

Buds ovoid, tomentose, dark brown, to 1 cm in length.

Leaves thick, elliptical, coriaceous, 7-15 × 2.5-6 cm, apex rounded or acute, margin entire, base truncate to rounded. The upper surface is dark green, the new growth is bright red (in young specimens there can be some teeth near the apex). Both surfaces covered overall with simple stellate hairs, dark brown at the base and along the veins, sometimes also on the margin. These hairs are far more abundant on the lower surface, which is of a slightly lighter color than the upper surface. There are 9-11 secondary veins, impressed on top and protruding below, joining together at the margin. The petiole is thick and covered in hairs, 0.5-1 cm long.

New growth 
New growth 

Cupules are hemispherical, light brown, darker towards the apex. They cover about one third of the acorn.

Acorns are oblong to conical
Acorns are oblong to conical, to 3.5 cm long by 1.5-2 cm wide

The acorns are oblong to conical, to 3.5 cm long by 1.5-2 cm wide, dark brown, with an elongated apex. Many (not all) of the acorns germinate laterally, like those of Q. corrugata. They ripen annually and cluster on a peduncle 7-10 cm long and 0.5-0.7 cm in diameter.

Detail of acorns showing lateral germination
Detail of acorns showing lateral germination

 

Ecology

It grows at an elevation between 2,500 and 3,000 m, in a cool tropical climate with high rainfall (cloud forest), in association with Q. copeyensis, Q. seemannii, Q. tonduzii, Billia hippocastanum, Drimys granadensis, Viburnum costaricanum, Oreopanax xalapensis, O. nubigenus, Clusia sp., etc.

Seedling of Quercus sp. from Volcan Barva
Seedling of Quercus sp. from Volcán Barva

It is most similar to Q. copeyensis, from which it differs by the oblong-conical acorns with an elongated apex. Q. copeyensis acorns are spherical with a rounded apex. Also the base of the leaf is truncated to rounded, while it is attenuate in Q. copeyensis.

Seedlings of Quercus copeyensis
Seedlings of Quercus copeyensis

Photos © Francisco Garín