Part 2: Adam Graves with more of the San Diego Zoo’s Horticultural Department

| June 5, 2021 | 0 Comments

The San Diego Zoo is known for its conservation efforts.  Familiarly called “Team Plant,” it is comprised of four sections.  First is San Diego Zoo which focuses on research, conservation,  direct science, education and outreach.  The second section is San Diego Zoo Institute for Conservation Research holding a seed bank with over 550 selections and 375 taxa.  The Institute dries and freezes seeds for future propagation and does genetic analysis. San Diego Safari Park, the third unit, provides safe sites for plants that need more space, providing the environment is appropriate. Finally, there is also the Center for Plant Conservation at San Diego Zoo Global whose mission is to unite expertise worldwide to save disappearing species.

The Zoo grounds house nine special accredited collections, including orchids, cycads, palms, bamboo, ginger, ficus, acacia, erythrina, and aloes.  Unofficial special collections are Hawaiian plants, caudiciforms, and carnivorous plants.  The Ex SituCollections are from other areas.  Normally removing plants from their natural habitat is not an acceptable way to collect them; however, moving endangered plants like the rapidly disappearing cycads, which have no safe habitat, is essential for securing a genetic repository for future conservation work. These collections educate and entertain the public as well. Keeping and verifying the botanical collection through our accessioning system* is really important proving: “We have what we say that we have.”

San Diego Zoo deals with Exceptional Endangered Species, species whose seeds are not easily stored and germinated.  Oaks, cycads and orchids are examples of these of particular concern to the Zoo. 

Climate change and invasive pests have caused our oaks’ decline.  Oaks’ acorns are viable only for six to twelve months. Normal freezing and drying seeds to preserve the trees doesn’t work.  The seeds need sufficient moisture to grow, but if they are not frozen and dried, they are susceptible to fungal infestation.  The Zoo works with five endangered species of oak found in California, Baja California, and the Islands of San Clemente.  To propagate these declining oaks, the staff grows seedlings from acorns. 

These are then given, never traded or sold, to various botanical gardens to grow and propagate.  Besides raising seedlings, the Zoo staff rely on science, such as micropropagation, which involves collecting live tissue, feeding it a rich cocktail, placing it in a special medium, freezing it with liquid nitrogen, thawing it, and planting the tiny root ball, which Adams says resembles a tiny meatball.

Cycads, on which dinosaurs feasted centuries ago, are threatened everywhere.  Their seeds cannot be dried and frozen; the safest method of preservation is moving them to safe environments.  Graves warns that slow-growing cycads “are not for people who want instant gratification.”  The sago palm is the fastest growing.  Two of the rarest cycads, between three and five hundred years old, grow in our Zoo.  One is the encephalartos latifrons; the other is the encephalartos woodii. In the wild are fewer than 65 of the former; the latter is extinct in the wild and all those remaining are male.  Cloning, hybridizing the clone and then back-crossing the clone is one possibility of reproducing it.  Graves is certain that whoever installed our cycads “sweated bullets” doing so.

 Whatever method works for creating a method of reproducing a plant on the brink of extinction, San Diego Zoo’s horticulturalists share successes, share plants, publish when they achieve a duplicatable result, and move on to the next problem.

The orchid is the third of our Zoo’s trio of Endangered Species.  Our Zoo has an enormous orchid collection with incredible diversity.  We have over 3000 plants, 161 genera, and 769 taxa.  One reason for our incredible collection is confiscation of smuggled plants.  Smuggling has caused many species to become endangered or extinct, especially in Southeast Asia.  In 1988, the California Department of Fish and Wildlife confiscated a plethora of plants.  The Zoo now has a specialist whose only responsibility is the care and propagation of orchids.  His collection grew exponentially in 1990 when a huge collection of paphiopedlila (slippered orchids) was collected. 

Orchids are quite difficult to propagate.  At the Zoo, they begin life in a micropropagation laboratory where the tiny seeds feed in tiny jars.  Once they are baby orchids or protocorms, they are shipped all over the world.  Propagators must supply immature orchids with a fungus in their environment as have a parasitic relationship with it until it is an adult and becomes independent. 

Because wild collections of orchids and subsequent illegal trafficking lead to the extinction of many species, in 2015 San Diego Zoo Global sent a crew to Palau, island home to the highest diversity of orchids in Micronesia, where they held a training workshop on seed collection, propagation, and storage. The staff also set up a plant nursery and a Palau intern trained with San Diego Zoo’s horticultural staff.  San Diego Zoo Global also helped launch a micropropagation laboratory in Palau. The goal is for Palau to create a revenue stream through propagation and conservation of orchids.

The Zoo’s horticultural staff is also responsible for growing food, called Browse, for many of the animals “from elephants to ants,” says Groves.  Each day a dozen elephants eat a staked truckload of Ficus, mulberry, acacia, and giant bird of paradise, Chinese elm, and any trees that fall.  Thirty acres is set aside for Browse, the areas that grow materials for the animals.  The food is placed to replicate the way it would be found in the wild.  Acacia is placed so giraffes must reach for their food.  The last two feet of eucalyptus are given to the finicky koalas who find the rest of the branch too tough.  The eucalyptus that grows profusely throughout San Diego County are toxic to koalas; they eat other less prevalent varieties.  One acre of eucalyptus will feed two koalas for a year.

One challenge the Zoo faces is pest control.  Obviously, pesticides are verboten.  Other methods of control are needed.  The South American Palm Beetle is our latest invader.  It lays its eggs in the tops of our Canary Island Palms.  The grubs literally eat the palm from the inside out.  These grubs are a delicacy in Southeast Asia, and they are high in protein. 

Another challenge is maintaining the landscape with the animals.  Pregnant animals require quiet; elephants and some primates are tough on trees.  Peacocks pick flowers.  Even the plants present problems as their roots destroy the infrastructure. 

We thoroughly enjoyed Adam Grove’s talk, and encourage you to contact him through the Zoo for a tour.  It will be well worth your while.

June 24 is the last meeting before September.  It will be a Zoom meeting from 6:30 p.m. to 8 p.m.   Chuck McClung will speak on How Orchids Rebloom. Reservations are required. Please visit for more information, and to register.

*Accession is a means of obtaining additions to a collection including information about it and its origins and often a receipt for its arrival.

Cycas circinalis, also known as the queen sago, is a species of cycad known in the wild only from southern India.

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Category: Education, Gardening, Historical, Local News, Nonprofit

About the Author ()

Barbara Strona is a native Californian who grew up in the Mid-West and Los Angeles. She and her architect husband, Carl, came to San Diego in 1968 and have lived in Mission Hills since early 1971. Barbara received a Bachelor of Arts from Scripps College with a major in English, and a minor in Art. She attended UCLA graduate school and received a General Secondary Credential. She taught English in Los Angeles, Pennsylvania, and at Point Loma High School. She has been a Realtor specializing in residential sales since 1984. Her passions include her job, reading, writing, foreign languages and foreign countries, animals (feathered or furry), theatre, and her family: husband, two adult children and two grandsons.