Arboretum Images 9

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Palomar College Arboretum Images 9: Cactus & Succulent Garden
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If you have driven along Mission Road past Palomar College during the past 50 years, you have probably noticed a large cactus and succulent garden at the east end of campus. This landmark garden actually had its beginnings in 1957 when a newly formed cactus club held its first meeting at Palomar College and elected Esther Nesbin as president and Mildred Gregory as secretary. The membership increased rapidly, including many members from San Diego, and soon a section split off to form the San Diego Cactus & Succulent Society. The Palomar group continued to expand, and in 1962 the Club Garden was established at its present 2 acre site on campus. Donations and a lot of work by various members provided a water line to the garden, pathways and numerous cacti, agaves, aloes and other succulents. The Governing Board of the College provided a chain link fence with locked gates to secure the valuable plant collection. In those early years, the garden was the site of picnics, workshops and auctions by many enthusiastic gardeners. During the past five decades, many of those original plantings have grown into splendid specimens and the collection has increased to many thousands of species from desert regions throughout the world.

Left: A large Yucca filifera with its characteristic pendant inflorescence. This Mexican species belongs to the agave family (Agavaceae). Right: A large elephant-foot tree (Beaucarnea recurvata) with Tillandsia epiphytes growing in the forks of its main trunk. This Mexican species has historically been placed in several different plant families; however, comparative DNA studies indicate that it belongs to the butcher's broom family (Ruscaceae) along with Dracaena, Cordyline, Dasylirion and Sansevieria.

Cacti and succulents include many plants in diverse plant families that have become adapted to arid regions of the world with low rainfall. They have similar morphological characteristics, an example of convergent evolution (homoplasy). Some have thickened stems and leaves that store water; some are drought deciduous and lose their leaves during the dry season; and some have leaves and stems modified into spines and thorns. For example, many North American cacti are remarkably similar in appearance to African euphorbias, until you see their very distinctive flowers. Some of the most bizarre plants on earth are in this group, including caudiciform trees, shrubs and vines that grow out of a huge basal caudex buried in the ground. When the entire trunk is unusually thickened like the baobab and bottle trees, the term pachycaul is used.

This pathway is lined by large Euphorbia quadrangularis native to Tanzania. In the distance is a Mexican blue palm (Brahea armata).

The Garden contains more than 3,000 species of drought resistant flowering plants, representing over 15 plant families. With all the recent research in molecular taxonomy, especially chloroplast DNA, there have been some drastic changes in the classification of plants, particularly their placement in different plant families. When all of these plants are in full bloom, the air is filled with the sweet scent of flowers and sounds of foraging bees and a myriad of butterflies and hummingbirds. One exception to the sweet aroma is the remarkable carrion flowers (Stapelia) of the Apocynaceae that are pollinated by blow flies and flesh flies.

The bizarre starfish flower (Stapelia gigantea) is a succulent member of the milkweed family (Asclepiadaceae) native to South Africa. The large flower has the scent of rotting carrion and attracts blow flies and flesh flies for pollination.

Another remarkable starfish flower native to South Africa (Stapelia variegata)

  See Wayne's Word Article About Stinking Flowers  

Two of the largest genera in the Garden are Agave (Agavaceae) with approximately 150 species and Aloe (Asphodelaceae) with 125 species. Other large genera are Opuntia and Mammilaria (Cactaceae) and Senecio (Asteraceae). In fact, the latter genus is one of the largest in the plant kingdom. There are also numerous species of Euphorbia (Euphorbiaceae), including large tree euphorbias that have been on the site for nearly 50 years. Pathways lead to 40 individual gardens, including Baja California, Arizona, Africa, Madagascar and the Canary Islands. Several gardens feature specific genera, including Pachypodium (Apocynaceae), Sansevieria (Ruscaceae) and Dudleya (Crassulaceae). Additional families include the spectacular proteas and leucospermums of the protea family (Proteaceae) and the beautiful drought resistant ice plants of the Aizoaceae.

Yellow pincushion (Leucospermum cordifolium), a lovely member of the protea family (Proteaceae) native to South Africa.

Oscularia deltoides (Aizoaceae), a colorful clumping ice plant native to South Africa.

One of the most interesting cactus species in the Garden is called dragon fruit (Hylocereus undatus). Native to Central and South America, this climbing cactus is cultivated throughout tropical regions of the world. In fact, it is commonly sold in marketplaces of Thailand. Our dragon fruit is especially unusual because it has climbed to the top of a tall deodar cedar (Cedrus deodora).

A dragon fruit cactus (Hylocereus undatus) that has climbed to the top of a tall deodar cedar (Cedrus deodara) in the Palomar College Cactus & Succulent Garden.

Dragon fruit (Hylocereus undatus), a beautiful climbing Central American cactus.

Freshly ripened dragon fruit (Hylocereus undatus).

  Dragon Fruits At Marketplace In Thailand  

This extensive collection was owned by the Palomar Cactus and Succulent Society and Dick Henderson, manager of the Garden. For the past 20 years, Mr. Henderson has donated countless thousands of hours to maintain this remarkable collection of plants from throughout the world. In an official letter dated February 2011, the Board of the Palomar Cactus and Succulent Society donated this splendid collection to Palomar College. Valued at approximately $400,000, the Cactus and Succulent Garden will be the most extensive garden on campus and a great asset to the college and to the community. This landmark along Mission Road in San Marcos will finally be part of the Palomar College Arboretum east of campus, truly one of the largest collections of plants in San Diego County.

Dick Henderson, manager of the Palomar Cactus & Succulent Garden.

For a tour of the Palomar Cactus and Succulent Garden, please contact Dick Henderson who leads
occasional group field trips throughout the year. You may contact Mr. Henderson at (760) 480-4181.