Overview
Like many other islands in the Caribbean, the history of St. Croix in the U.S. Virgin Islands is inextricably bound up with the planting and harvesting of sugarcane. Decades of land clearing for sugar plantations, as well as cotton and livestock, denuded the U.S. Virgin Islands of more than 90% of its native vegetation. Agave eggersiana is a succulent, endemic to St. Croix and is known locally as St. Croix agave or Egger’s century plant. It once flourished in the subtropical dry forests of St. Croix, but neared extinction due to widespread change and elimination of its habitat. Today, only small pockets of the plant remain on an island with a total area of 84 square miles. Agave eggersiana was listed for protection in 2014 under the Endangered Species Act.
This hardy plant can grow to about 5 feet tall and send up an inflorescence, or spike, that may grow more than 20 feet high. The attractive spike of yellow flowers turn orange over time and may be one factor that has contributed to its survival: it has been used in private landscaping. However, it still struggles for a foothold in the small, protected areas available on St. Croix. After flowering, the panicles, or clusters of flowers, produce numerous small vegetative bulbs, also known as bulbils, which fall off to produce new individual plants. Agave eggersiana is not known to produce fruit containing viable seeds, and, like other agave species, it is monocarpic, meaning the plant dies after producing the flowering spike or inflorescence.
Agave eggersiana can take 10 to 15 years to develop into a mature reproductive adult, and longer dry spells mean that it takes even longer for the plants to mature. There are plants on St. Croix that are known to be more than 30 years old. The U.S. Virgin Islands is expected to experience prolonged dry periods and higher temperatures due to climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change , which could result in individual A. eggersiana taking longer to mature.
One of the most consistent threats to Agave eggersiana since its listing is development and unregulated land clearing on St. Croix. As the species does not create seeds necessary to establish a natural seed bank, once land is cleared there is no chance of the species re-establishing.
Currently, the U. S. Fish and Wildlife Service and partners are supporting propagation projects for the species. Establishing new self-propagating populations of the species is important for maintaining the species redundancy, meaning the ability for the species to survive catastrophic events. We are contributing to the propagation, planting and enhancement of habitat for Agave eggersiana on private lands, as well as public protected lands on St. Croix. Reintroductions across the island will increase the present range of the species and enhance population connectivity between private and public lands.
Scientific Name
Identification Numbers
Characteristics
Physical Characteristics
Agave eggersiana is comprised of rosette of spiny, succulent and leathery leaves. The leaves have spines along the edges and at the tip. This species is typically dark green to greyish with bright yellow flowers. Not much is known about the reproductive process in A. eggersiana. The species is thought to utilize asexual reproduction, through the production of bulbils. Further genetics work is necessary to fully understand the reproductive process of this species.
Agave eggersiana is a robust perennial herb in the Agavaceae family of the century plant family, that are found primarily on the dry eastern side of the Island of St. Croix in the U.S. Virgin Islands. This species does not form offshoots around its base and leaves are thick, fleshy and nearly straight. This agave species grows into a kind of sphere and the diameter may be up to 5 feet long. Agave eggersiana reproduces only once in its lifetime by producing a tall spike about 20 feet high, called an inflorescence. Deep yellow flowers develop into numerous loose branching clusters, or panicle, and eventually develop into small vegetative bulbs, or bulbils. The spike then falls dispersing bulbils away from the mother plant.
Life Cycle
Once bulbils form on the panicle of the inflorescence, they typically fall to the ground once the weight of the bulbils is too much for the inflorescence. The entire inflorescence falls over and bulbils, as small as 2 to 20 centimeters in length will establish themselves in the ground. These bulbils can mature within 10 to 15 years under optimal conditions, however, long draughts prolong development to adulthood or reproductive age. Once an individual reaches reproductive age, it will send up an inflorescence that will develop a panacle of bright yellow flowers that will eventually become the bulbils. Each individual plant can produce about 100 to 200 bulbils.
There has been little research done on Agave eggersiana in the past. The actual life span is unknown. Individuals of the species may reach maturity in 10 to 15 years under optimum conditions, but it is unknown how long they can survive under drought conditions which hamper their development.
There has been little research done on this species, it is currently believed that the species reproduces via asexual reproduction. The species does have flowers and produces vegetative bulbils, however, genetic work would be necessary to draw any formal conclusions. Interestingly, in 2019 a local biologist on St. Croix observed an unknown structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.
Learn more about structure on a fallen inflorescence that resembled a seedpod. This observation suggests that mechanisms for sexual reproduction may be present in the species.
Habitat
Although reported from the hillsides and plains of the eastern portion of St. Croix in the 1900s, Agave eggersiana is currently limited to coastal cliffs with sparse vegetation and dry coastal shrubland vegetation communities within the subtropical dry forest life zone of St. Croix, U.S. Virgin Island, as documented by the Virgin Islands Department of Agriculture in 2010.
St. Croix contains two life zones: subtropical moist and subtropical dry forests. Subtropical dry forests make up 72% of the island, while the other 28% is subtropical moist forest, as documented by the Virgin Islands Department of Agriculture in 2010. Forest characteristics are diverse from site to site due to the history of land use. Dominant forest types on St. Croix are deciduous, evergreen mixed forest, shrubland with succulents, drought-deciduous young forest/scrub and semi-deciduous forest/scrub. Young forests and scrubs, indicative of recent disturbance, are dominated by the non-native tan-tan (Leucaena leucocephala) and casha (Acacia macracantha), as documented by the Virgin Islands Department of Agriculture in 2010.
Land on which the natural dominant plant forms are grasses and forbs.
A dense growth of trees and underbrush covering a large tract.
Arid land with usually sparse vegetation.
The land near a shore.
Geography
Agave eggersiana is endemic to the island of St. Croix in the U.S. Virgin Islands. Historical distribution of the species throughout the island is unknown due to the loss of indigenous habitat for agricultural uses in the past. By the time the U.S. Virgin Islands were acquired from Denmark by the United States in 1917, it is estimated that 90% of St. Croix had been cleared for agriculture and logging, as noted by T. Brandeis and M. Charkroff in 2010. In the early 1900s, the species was reported from hillsides and plains in the dry eastern districts of St. Croix, currently, Agave eggersiana is primarily limited to coastal cliffs with sparse vegetation.
Timeline
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