Cook's holly (Ilex cookii)

Cook's holly specimen
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Cook's holly fact file

Cook's holly description

GenusIlex (1)

Named after one of its discoverers, Melville Cook, this incredibly rare evergreen species was first collected during early botanical explorations of Cerro de Punta, Puerto Rico’s highest mountain. Cook’s holly grows as a small tree or shrub, with light-brown bark and hairless, green twigs. The leathery, elliptic leaves are arranged alternately on the stem, and have a shiny, dark-green upper surface, and a pale green lower surface (2) (3). No male flowers of this dioecious species have ever been observed, but the female flowers are small and white, and the fruit is a berry (1) (3) (4).

Max height: 2-3 m (2)

Cook's holly biology

As might be expected of such a rare plant, almost nothing is known about the life history of Cook’s holly. 


Cook's holly range

Cook’s holly is endemic to the two highest peaks in Puerto Rico, Cerro de Punta and Monte Jayuya, both of which lie within the Toro Negro State Forest. The entire known population is limited to single, mature tree near the summit of Cerro de Punta and a scattering of seedlings on the ridgetops on Monte Jayuya (1) (3). However, given the limited extent of the high-elevation elfin forest in which it is found, Cook’s holly has probably never been especially abundant (2).


Cook's holly habitat

Cook’s holly is restricted to the dwarf or elfin forest that occurs at high elevations in the central mountains of Puerto Rico. These forests are dominated by gnarled, densely branched tress, which form a low canopy rarely exceeding seven metres (1) (2) (3).


Cook's holly status

Classified as Critically Endangered (CR) on the IUCN Red List (1).

IUCN Red List species status – Critically Endangered


Cook's holly threats

Having last been reviewed on the IUCN Red List in 1998, the conservation status of Cook’s holly is in urgent need of updating (1). The construction of communication towers on Cerro de Punta is thought to have destroyed a large part of the original population, with further development and construction activities being cited as the main threat to the remaining plants (1) (3). The highly restricted range of Cook’s holly also makes it extremely vulnerable to natural disturbances such as landslides and hurricanes (2).


Cook's holly conservation

Cook’s holly was listed on the US Endangered Species Act in 1987, and a Recovery Plan was drawn up by the US Fish and Wildlife Service in 1991 (1) (2). Several necessary actions were outlined in the plan, including: the protection and monitoring of existing populations; the undertaking of research into the species’ life history and reproductive biology; and the propagation of seedlings for the enhancement of existing populations and the establishment of new ones (2). However, since none of these measures appear to have been implemented thus far (5), an up-to-date evaluation of the condition of the remaining plants seems to be seriously overdue.


Find out more

To find out more about Cook’s holly, see:



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Male and female flowers are borne on separate plants.
Elfin forest
Type of tropical high altitude forest, growing on exposed sites in which the trees are dwarfed or gnarled.
A species or taxonomic group that is only found in one particular country or geographic area.


  1. IUCN Red List (January, 2010)
  2. U.S. Fish and Wildlife Service. (1990) Ilex cookii and Cyathea dryopteroides Recovery Plan. U.S. Fish and Wildlife Service, Atlanta, Georgia.
  3. Densmore, D. (1987) Endangered and Threatened Wildlife and Plants Determination of Endangered Status for Cyathea dryopteroides and Ilex cookii. Federal Register, 52(115): 22936-22939.
  4. Heywood, V.H. (1978) Flowering Plants of the World. Oxford University Press, Oxford.
  5. U.S. Fish and Wildlife Service (January, 2010)

Image credit

Cook's holly specimen  
Cook's holly specimen

© New York Botanical Garden

The C. V. Starr Virtual Herbarium of The New York Botanical Garden


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