Arboretum Newsletter 10

Edwin and Frances Hunter Arboretum

Palomar College Received Generous Donation From The Hunter Family

The Palomar College Arboretum will be renamed the Edwin and Frances Hunter Arboretum after the cofounders of Hunter Industries in San Marcos. The Arboretum received an endowment of $500,000 from the Hunter Family Fund and Hunter Industries, makers of high quality irrigation equipment and controllers.

The Hunter family came to San Marcos 35 years ago to open Hunter Industries, a global irrigation products company with 800 local employees. Ann Hunter-Welborn remembers the very moment when she decided to endow the Palomar College Arboretum in her late parent's name. While walking through the stately conifers and massive Moreton Bay and Mysore figs, she was impressed by their beauty and wanted to protect them.

In addition to Palomar College, the Hunter Family Fund has supported Center Artes at Cal State San Marcos, the San Marcos School District's Fortissimo Children's Orchestra program and North County Health Services, which operates two clinics for low-income patients in San Marcos.

The Hunter Family believes in the preservation of forests and greenbelts. "Palomar College is such a vital asset to our community, and having walked through the arboretum, it's clear this wonderful garden is important to students and is a value to the community. Green spaces are crucial to the future of our world." said Ann Hunter-Welborn. Improvements to the Arboretum are part of Palomar's Educational Master Plan, funded in part by Proposition M, approved by voters in November 2006. It will include an irrigation system and wheelchair accessible trails throughout the Arboretum.

A Caprifig Now Planted On Campus

This Is Pollinator For The Most Delicious Edible Figs

In the early 1980s I took a cutting from a wild fig growing along a roadside in Vista. It resembled a common fig (Ficus carica) except the fruits were purple and a little smaller than common figs. I compared it with fig trees grown in test plots at the University of Riverside and it appeared to be Ficus pseudocarica. During the 1940s through 1970s, fig authorities Drs. Ira J. Condit and William B. Storey conducted research on the taxonomy, pollination and genetics of cultivated figs. Over the years the taxonomic status of F. pseudocarica has been debated by botanists. F. pseudocarica is listed as a synonym of F. palmata (Punjab fig) in the Kew List Of Plant Species (2011).

According to Condit (1955), Ficus pseudocarica is native to Eritrea and Abyssinia, while F. palmata is indigenous to Pakistan, northern India and Afghanistan. He states that F. pseudocarica was introduced into Santa Barbara, California in 1902, and like F. palmata, was used for hybridizing with F. carica. In fact, the edible 'Brawley' caprifig cultivar is a hybrid between F. carica var. 'kadota' and a F. pseudocarica caprifig (Storey et al. 1977). Ficus palmata is commonly used in modern floras, with F. pseudocarica listed as a synonym. Alan Whittemore (2006) has studied herbarium collections of F. palmata (F. pseudocarica) from California and has concluded that they are misidentified and should be labeled F. carica. Recent DNA studies indicate that it is closely related to F. palmata or belongs to a Ficus carica species complex. I will continue to call it F. pseudocarica because it sure matches the tree I photographed at UC Riverside (Figure 1).

Figure 1: Ficus pseudocarica and F. palmata at test plots of UC Riverside in June 1985.

According to Ira Condit's monograph on fig varieties (1955), the caprifig of this species has a distinctive profichi syconium that is purple-black in color with a long, slender stalk (peduncle). In his classic volume The Fig (1947), Condit describes the syconium as smaller than other varieties of F. carica. In Ficus: The Exotic Species (1969), Condit describes the twigs of F. pseudocarica as velvety pubescent and the twigs of F. carica as glabrous or only slightly puberulent when young. F. pseudocarica is listed as a synonym of F. palmata (Punjab fig) in the Kew List Of Plant Species (2011). It is listed as naturalized in California (under F. palmata) in the Calflora Database and USDA Plant Database. According to the revised Jepson Manual (2011), reports of F. pseudocarica and F. palmata are based on misidentified specimens of F. carica (A.T. Whittemore, 2006, Sida 22: 769-775).

The actual edible "fruit" of a fig tree is called a syconium--a hollow structure lined on the inside with hundreds of tiny unisexual flowers. A tiny female wasp (Blastophaga psenes) enters an opening on the syconium to pollinate the flowers. In Ficus carica, only the syconia of female trees are edible, and without pollination they typically do not ripen and fall from the branches. Male trees, called caprifigs, produce inedible syconia containing wasps and pollen-bearing male flowers. [Capri refers to goat and the syconia were apparently fed to livestock.] During the late 1800s, Calimyrna fig growers in California were puzzled why their trees would not set fruit. They discovered that the female trees needed the fig wasp and male caprifigs from the Old World. Each June in California's hot Central Valley, bags of wasp-bearing caprifigs are placed in the Calimyrna orchards (Figure 2). This amazing pollination process is called caprification and the crunchy, seed-bearing syconia have a superior nutty flavor. Premium fig newtons are made from caprified figs and contain numerous seed-bearing nutlets (Figure 3).

Figure 2: Each June in California's hot San Joaquin Valley, paper bags containing wasp and pollen-bearing caprifigs are stapled to limbs in Calimyrna fig orchards. Only a few wasp-laden caprifig syconia are placed in the bags to prevent overpollination and split caliper fruit. Inside the paper bag (right), small black wasps can be seen exiting the caprifigs.

Figure 3: A wasp-pollinated Calimyrna fig containing numerous seed-bearing nutlets or drupelets (minute ripened ovaries). In fact, the excessive pollination and seed production has caused the syconium to split open. The seed-bearing drupelets impart a superior nutty flavor to the fig newton (right).

My Ficus pseudocarica is a male tree bearing inedible syconia laden with pollen from male flowers and bearing hundreds of fig wasps. It produces three crops of syconia per year, including an overwintering crop when the tree is leafless which perpetuates the wasps during cold winter months. Tony Rangel planted cuttings from my tree in the African Garden near the Theatre Building. This is a good location since the Ficus carica species complex is native to colder climates of Turkey and the Middle East. The other 800+ species of Ficus are native to tropical continents and islands throughout the world.

Annual Crops Of Ficus carica & F. pseudocarica syconia

Sex of Tree
Mature Crops Of Syconia Per Year
Male Caprifig
Profichi (June) *
Mammoni (Fall)
Mamme (Winter)
Female Tree
1st or Breba (Summer)
2nd or Main (Late Summer-Fall)

* Only the caprifig profichi crop produces pollen, and this is used to pollinate the immature, receptive main crop in June by the action of winged female fig wasps. This main pollinated crop ripens in late summer-early fall. The mammoni crop is produced during the fall months followed by a mamme crop that remains on the leafless branches during the cold winter months. Wasps inside the mamme crop will enter the immature, receptive profichi crop in spring.

There are hundreds of parthenocarpic varieties of the common fig (Ficus carica), including 'Mission' and 'Kadota' in which the seedless syconia ripen without pollination. According to fig connoisseurs, pollination produces a more delicious fig with a superior nutty flavor due to the seeds. The remains of parthenocarpic fig syconia in ancient settlements of the Jordon Valley indicate the people recognized natural parthenocarpic trees and propagated them by cuttings more than 11,000 years ago. This may be one of the earliest forms of agriculture.

The fig and fig wasp pollination story is very complicated. It is exceedingly difficult to make a generalized explanation in front of an audience because there are so many exceptions depending on the fig species. During my career at Palomar College I have studied many subjects, from duckweeds, drift seeds and brodiaeas to ants; however, I must say that the coevolution of the 830 fig species and their symbiotic wasps is the most complicated and fascinating. So the next time you bite into a fig newton, think about the history of this tree and its symbiotic pollinator wasp, and how it affected our lives by providing food and itchy leaves for the first naked humans.

Fig References Cited In This Newsletter

  1. Condit, I.J. 1955. "Fig Varieties: A Monograph." Hilgardia: 11: 323-538.

  2. Storey, W.B., Enderud, J.E., Saleeb, W.F., and E.M. Nauer. 1977. The Fig. Jurupa Mountains Cultural Center, Riverside, California. [Available From: California Rare Fruit Growers Market Place

  3. Whittemore, A.T. 2006. "Notes On Southwestern Moraceae." Sida, Contributions To Botany 22: 769-775.

  More Information About Figs On Wayne's Word  
Fig Species In The Palomar College Arboretum
Links To Articles About Figs On Wayne's Word

A Rare African Tree In The Campus Greenhouse

Gigasiphon macrosiphon: A Seed That Resembles Mucuna

Horticulturist extraordinaire Tony Rangel recently germinated some seeds of Gigasiphon macrosiphon, a rare leguminous tree known only from moist, lowland and coastal forests of Kenya and Tanzania. According to Encyclopedia Of Life (EOL), destruction of East African coastal forests and the use of this tree for firewood, tools, charcoal and lumber has reduced its population to 33 known mature individuals in the wild. The International Union For Conservation of Nature (IUCN) assessed G. macrosiphon with "Red List Endangered Status" in 1997, and in a report in conjunction with the Zoological Society of London (ZSL) places this species on their list of 100 most endangered species in 2012. According to the Foster Botanical Garden in Honolulu, Hawaii, this unusual tree may be extinct in the wild.

The seeds are remarkably similar to those of tropical lianas in the genus Mucuna. These large woody vines are known as "seabeans" because the thick-walled, buoyant seeds are carried down streams into oceans where they float to shores of distant continents (Figure 4).

Figure 4: The seeds of Gigasiphon macrosiphon resembles those of sea beans (Mucuna). The tough, indehiscent seed pod contains two seeds and they appear to be adapted for drifting in water.

The seeds of this remarkable tree came from a tree at Foster Botanical Garden in Honolulu, Hawaii. They have been in a paper bag for the past 16 years. Tony used a metal file to scarify the thick, woody seed coat on both flat sides. He then soaked the seeds in water for 18 hours and planted them in a fast-draining commercial seed mix. This technique also works for seeds of tropical vines (lianas), including seabeans (Mucuna & Dioclea), and sea hearts (Entada gigas). I have collected the latter drift seeds along numerous seashores, thousands of miles from their native rain forests. Special thanks to the Honolulu Botanical Gardens for allowing us to propagate this magnificent African tree.

Some species of seabeans are called "hamburger seeds" because of their resemblance to a miniature hamburger (Figure 5). I became fascinated with seabeans on beaches of the Caribbean, Mexico and Central America. I even found them on the Galapagos Islands. According to B. Verdcourt (Kew Bulletin Vol. 36 No. 4, 1982), the Mucuna illustration on page 161 of "World Guide to Tropical Drift Seeds and Fruits (Fig. 66 (A-D)" is actually from Gigasiphon. The caption reads "Beaches of Canton Island." This is a South Pacific island approximately half way between Hawaii and Fiji, so Gigasiphon is clearly a drift seed species capable of long ocean voyages.

Figure 5: A sea bean Mucuna gigantea ssp. gigantea collected on a West Maui beach on 22 November 2012. It truly resembles a miniature hamburger, especially when compared with an order of fries! I must confess that I greatly reduced the size of the plate and fries. The sea bean is only 22 mm in diameter (just under one inch).

The large blossoms of Gigasiphon are very different from the pea-shaped (papilionaceous) flowers of Mucuna (Figure 6). Gigasiphon actually belongs to a different subfamily, the Caesalpinioideae. It is more closely related to orchid trees (Bauhinia) than Mucuna.

Figure 6: Although the seeds of Gigasiphon macrosiphon resemble Mucuna species, the large blossoms are very different from the pea-shaped (papilionaceous) flowers of Mucuna (subfamily Papilionoideae = Faboideae). Gigasiphon actually belongs to a different subfamily, the Caesalpinioideae. It is more closely related to Bauhinia than Mucuna.

  More Information About Seabeans On Wayne's Word  

A Plea For Volunteers To Work In The Arboretum

We Also Need Committee Members For Friends Of The Arboretum

On a recent road trip to Arizona, I visited the Boyce Thompson Arboretum, Tucson Botanical Garden and the Arizona-Sonora Desert Museum. One thing in common about these outstanding botanical gardens is their large, dedicated staff of volunteers. This is true of other impressive arboretums throughout the continental U.S., Canada and the Hawaiian Islands. A handful of people is just not enough. As our Arboretum is improved with trail and irrigation systems, we also need volunteers to serve on the Friends of the Arboretum committee. Please visit the Arboretum home page for more information:

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Become An Arboretum Volunteer
Become An Arboretum Member
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Newsletter Articles By W.P. Armstrong, March 2016