Frank Escobedo, a senior horticulturist at the Wild Animal Park, tells of the dangers of having eucalyptus trees. They have weak trunks and bark, which can cause fractures on the tree and lead to falling branches.

The cycad is a prehistoric conifer that is related to the pine tree, hence the large cones in the center. Mr. Escobedo told us of his passion for growing these huge trees in his backyard.

Growing very tropical plants outside has been tried at the Zoo before, but the problem of cool, damp soils in the winter seems to be the biggest killer. The cacao plant Theobroma cacao, source of chocolate, comes from the tropical rain forests of Central and South America–places that rarely get colder than 60 degrees. How could we create an environment where a cacao tree could survive outdoors in cooler temperatures? An idea came to Mike Letzring, the Zoo’s Horticulture Collection Manager. His plan was to create a heated area in the soil just below the plant, similar to heat benches for seed germination in greenhouses. This would help keep the roots warm all winter long.

With our plan in hand, we began our “chocolate experiment” in an area off-limits to the public. First, what was needed was a chocolate plant; luckily there were several growing in our greenhouse. Next, we built a 30-inch box made of insulation board, the kind you would use to insulate walls in homes and other buildings. After making drainage holes in the bottom of our insulated box, we added a few inches of well-amended soil. Our heat source, heating cables regulated by a control box, was coiled out and laid on top of the soil. Six more inches of soil was placed on top of the heating cables. Once the chocolate plant was planted and backfilled, a layer of mulch was spread over the whole area.

Over the course of the experiment, regular soil and air temperatures will be taken and recorded. This information will come in handy to us if our planting is successful. Although this very cold winter has been uncomfortable, the low temperatures will actually work to the advantage of the experiment, in that they provide an extreme temperature variable. Check back in a few months for an update on how our chocolate plant is doing. Who knows…maybe sometime down the line we’ll be able to make our own chocolate bars!

Seth Menser is a gardener at the San Diego Zoo.

The Zoos’ collection of aloes is comprised of 114 taxa and is one of the largest in California. The plants range from the small 6-inch miniatures to the tree-like Aloe bainesii, of which we have four on grounds that are over 12 feet tall. In their native habitat, they grow in the rocky hills of South Africa, mainly in full sun. They do not take frost but some in hotter areas like partial shade. Water requirements are little, but they will take additional amounts of water if given (see Weblog, The Aloe Tree).

Aloes will grow as solitary specimens or as large clumps like the “tree-like” species Aloe arborescens. If you get an aloe plant, be sure to confirm the species, as certain ones can be a problem of large magnitude if they grow too big for your space. They can take over an entire area by their spreading habit. Always keep in mind that they are armed and working with them can be hazardous and painful if you are punctured. However, looking at them can bring great pleasure–come to the Zoo and enjoy our bloomin’ aloes!

Mike Bostwick is the horticulturist for the San Diego Zoo.

The plants are looking pretty amazing considering night temperatures are really beginning to dip here in San Diego, down into the low 40’s (sorry if you’re in Buffalo reading this- I don’t mean to gloat). The sundews Drosera species (pictured) are looking about as good as ever. As I mentioned in my last blog, the flytraps Dionaea muscipula are about the worst of the bunch. Really, though, they look pretty good- just a little small. I’m beginning to see the effects of winter a little bit on the pitcher plants Sarracenia species. The flowers have dried up. I have continuously been cleaning out dead pitchers. However, the ones that are still alive look as beautiful as the day I met them. I even see some immature pitchers peeking up their little heads from the peat. For many plants in San Diego, the weather can be very confusing. I’ve watched many a neurotic deciduous tree drop its leaves, then put on new ones a month later, only to drop them again. We get cold nights often while the days feel just as warm as summer. Warm Santa Ana winds off the desert make it even harder for many plants from elsewhere to know what time of year it is.

The Sarracenia have been the backdrop for the Bog Garden since it was established. The tallest ones, the yellow pitchers Sarracenia flava, white pitchers Sarracenia leucophylla, and Judith Hindle hybrids grow as tall as 24 inches (61 centimeters). The purple pitcher plants Sarracenia purpurea and hooded pitcher plants Sarracenia minor are quite squat in comparison, and so they are set toward the fore of the bog, behind the sundews and flytraps. These wonderful and stunning carnivores eat heartily. I hardly ever see a bug actually going in. When I cut out the dead pitchers, however, I find them full of bees, beetles, and other assorted prey. The largest thing I’ve found so far—and there are lots of them—are the fig beetles. If you have an edible fig tree in your yard, you know this beetle well. It’s the big, green iridescent guy with the loud buzz. They can get to be over an inch long. They must provide some pretty good nutrition for our pitcher plants, but it also seems they might take some effort to digest!

I’ll continue to monitor the bog as things cool down. Even as it gets chillier, we will continue to plant more items that should do well. Judy Bell (who has been gardening in the Zoo since 1987 and in the Heart of the Zoo area since it opened in 1991) has been growing lots of extra bog plants. We are planning to add up to 20 new sundews next week from her nursery. If you happen to be around the Zoo, come by and check out the new plants!

Mychael McNeeley is a senior gardener at the San Diego Zoo.

The Zoo’s Euc forests played a large part in what the San Diego Zoo was all about in its beginning and through the years when bioclimatic zones were put in place for the development of its exhibits in the 1970s. They are key to our being able to keep koalas in our collection, in that we are able to provide around 36 different species of eucalyptus to them through our browse program. We were losing our overhead canopy and that was 80 years’ worth of growth. If we started right away, a replacement canopy could not be grown in our lifetime, so it was important to develop a long-range plan for reestablishing the upper canopy for the Zoo and to make it something that was unique and complemented the direction for our horticulture collections.

With the establishment of a reforestation fund, we set out to complement the bioclimatic zones of the Zoo with trees that matched the areas we established them in. We looked at trees with economic value like shade-grown coffee, fruit and nut trees, and trees that were endangered in their home habitat. We were able to build on some of the established collections. We planted the trees in groves where possible and at least did companion planting’s of like planting material. An example of that is our geographic-based collections like the Madagascar, Mediterranean, and Hawaiian gardens.

We’ve recently worked on the area just below the camels. That area was an old browse area where the trees outgrew their usefulness and became an eye sore. It was re-established as a New World planting area with Chorisia, Tabebuia, Chiranthodendron, and Brighamia species. In a few years, as the trees take on more size, it will become a vibrant area with unusual, blooming trees of aesthetic and educational value. Further down the canyon is another area that has been cleared of iceplant and will be supplemented with additional plantings that tie it into the Mediterranean Garden.

A new, large-scale project which was the impetus to write this blog was just recently started on the hillside behind the Migratory Duck Pond. This is a major project and changes the face of that area quite drastically. There was a real fire danger on that hillside and the trees were in very poor condition, including the safety aspect of some of them. After evaluations were done, trees marked, and bids secured, work began in earnest and the area was started towards a new beginning. Large trunks were left crossways on the slope for erosion control, debris was chipped to provide mulch back on the slope, and a new irrigation system will be installed. The bottom of the slope will be used for browse trees (acacia, fig, and mulberry); the upper two thirds will be reforested with specimen trees that are indigenous to the New World. It will become a useful and aesthetic part of our horticulture collections and not just a tired old hillside.

Mike Bostwick is horticulturist for the San Diego Zoo.

The most challenging species is also the most recognized. Venus flytraps are endemic to North Carolina and ranging a bit into South Carolina. These predators of the Plant Kingdom endlessly fascinate both kids and adults. Many a child has brought home a Venus flytrap at some time and killed it. Many times what does the plant in is the wrong kind of water. Carnivorous plants can’t take tap water. We run deionized, or DI, water through the Bog. Our challenges don’t come from the water, but instead from people and other critters.

The first flytraps went into the Bog just before opening Monkey Trails in June, 2005. Flytraps do most of their growing in the warm season. One of the earliest issues we had was humans wanting to see the traps up close. It is, after all, an amazing thing to touch a plant and see it react so quickly, its jaws snapping shut. Unfortunately, though, this wastes a lot of the plant’s energy without any reward. Actually, Charles Darwin theorized that the reason the jaws don’t close all the way is to allow smaller prey to escape, since the payoff isn’t worth the energy it takes to digest them. I used to find a lot of small pieces of grass or sticks that guests had thrown into the Bog in order to try to get the traps to close. I put up signs asking to please not throw things in, and for the most part, this seems to be working. Mostly it’s just that folks don’t know it will hurt the plants.

So, first humans, and then the ducks started coming! I walk by the Bog every morning around 6 a.m., and for months last fall and winter I found wild ducks happily trouncing around the bog, splashing in the watercourse, walking all over the plants, and, worst of all, leaving their “fertilizer” all over the Bog. I spent many a late morning with rubber gloves removing that duck stuff from the surface. Carnivorous plants grow in the poorest of soils, and they don’t like fertilizer. While the duck excrement would probably be great for most plants, it was destroying many of the Dionaea and Drosera in the Bog.

For a solution, we started adding some mangled long sticks around the edges of the garden, hoping it would discourage the ducks. It looked like they were walking, as opposed to flying in. So we thought maybe we could artfully blockade the area. It did help. We also decided to completely remove the “watercourse,” a small stream running through the center of the Bog providing all of the water circulating through. We ended up using a drip tube run across the area where the watercourse had been, with microjet risers to add water to the Bog, hopefully without too much pooling. So far, so good! The ducks have all gone back to Flamingo Lagoon, it seems. I haven’t seen one in the Bog in months. Winter is coming, though. The flytraps are beginning to go into their dormancy period. If we can keep the ducks out, perhaps they will make it through the winter. Time will tell.

Mychael McNeeley is a senior gardener in Monkey Trails at the San Diego Zoo.

Hibiscus rosa-sinensis (rose of China) is a widely used shrub in the Zoo. They are not only handsome plants, adding splashes of tropical color and verdant foliage throughout the landscape, but they also provide delicious browse for many of our primates! Sirena, from our Browse Department, collects hibiscus daily and distributes it throughout the Zoo. Monkeys enjoy the leaves, but the flowers are the icing on the cake. Browse serves several purposes. It is edible, providing nutrition, plus it gives the animals something to play with (enrichment). We are fortunate in San Diego to be able to grow such a wide array of edible treats that look so attractive in the landscape. Lush, often suitable to eat, landscaping helps create the ambience that makes the Zoo such a special place.

Some of the hybrid hibiscus you will find around Flamingo Lagoon are ‘Heavy Metal’ (pictured above), ‘Crystal,’ ‘Gerald Derr,’ ‘Gypsy Music,’ ‘Rainbow Christie,’ and ‘Rosalind.’ Other varieties are placed across from the Reptile House and along the main road from Flamingos to Gorilla Tropics. There are enticing names like ‘Flash Dancer,’ ‘Renaissance Blue,’ ‘Georgia’s Pearl,’ and ‘High Voltage.’ The word “flamingo” is derived from the Latin flamma, meaning flame or flaming. These showy hibiscus blossoms do pair well with the elegant birds they frame!

Mychael McNeeley is a senior gardener at the San Diego Zoo.

With over 1,800 living palm trees, the San Diego Zoo is proud to boast a very high concentration of unusual and exotic species from all around the world. Our large and varied collection of palms is accredited by the American Association of Museums, an honor in which the Zoo takes a lot of pride.

Ranging from tropical rain forests to deserts, the Arecaceae family is diverse and adaptable. The only thing that will limit the habitat of palms is extreme cold. Leaf structures are grouped into two types: palmate (fan) and pinnate (feather). One exception to this is the fishtail palm Caryota ssp, which produces bipinnate fronds. Like the famous coconut, many palm seeds are edible and can range in size from that of a pea to that of the 45-pound (20-kilogram) coco-de-mer palm seed Lodoicea maldivicia, which is the largest seed in the Plant Kingdom. A multitude of shapes and sizes, along with different shades of green, give palms their unique and sought-after qualities.

Some of the more popular palms at the San Diego Zoo are scattered throughout the grounds. As visitors walk through the entry gates, the main plaza opens up and they are greeted with a very large Cuban royal palm Roystonea regia (pictured above) on the shore of Flamingo Lagoon. With its stately concrete-colored trunk and lime green arching fronds, it’s hard to miss. When it’s time to go home, a group of them shade the exit breezeway. Having lunch at Sydney’s courtyard, you feel as if you are in a Middle Eastern date grove, with towering date palms Phoenix dactylifera overhead. In Cat Canyon, next to the hornbills, you will find one of the largest palms we have: an enormous fishtail palm Cayota gigas reaching upwards toward the sky. This palm has multiple, 30-foot (9-meter) bipinnate leaves that, like the common name implies, resemble many fish tails. Just about every area of the Zoo has palms except, of course, Polar Bear Plunge.

The San Diego Zoo’s gardeners take pride in maintaining and showcasing the ever-expanding palm collection here. With so many rare species growing at the Zoo, the Horticulture Department has put together several palm and botanical guides to help visitors locate our featured specimens. These guides are free and can be found at the main plaza to be used as a self-guided tour.

Seth Menser is a gardener at the San Diego Zoo.

Read Seth’s previous blog, Climatic Influences.

San Diego has a Mediterranean climate, which means summers are long and dry, often with foggy mornings. Although we don’t get much rain, it does come in the winter, from large moisture-ridden storms off the Pacific. Very mild temperatures can be expected all year round, and attribute for the so-called “perfect climate.” A quick check of records taken at the airport since 1872 shows that only nine days have ever experienced frost. In fact, 10 to 15 years can pass without once having freezing weather! People back east are shoveling snow in January, while here in San Diego our average winter high is 67 degrees Fahrenheit (19 degrees Celsius). Our climate makes it livable for both humans and exotic flora from arid to subtropical regions.

The thing I hear repeatedly from guests visiting the San Diego Zoo is how beautiful and lush our plants are. Many are amazed to see plants that they grow indoors back home growing outdoors and reaching very large sizes here at the Zoo. Our skilled gardeners use San Diego’s wonderful climate to cultivate plants taken from all points around the globe. Numerous large ficus trees shade areas beneath which we plant a whole other world of exotic under-story plants. Eye-catching orchids hang down from branches, cycads form miniature forests, and coffee plants fill in areas not touched by the sun.

In areas of full sun, countless unique species become priceless specimens, including every color of tropical hibiscus imaginable! Our reliable climate and the lack of extreme weather grants the San Diego Zoo the ability to create a diverse, enticing plantscape for all of our animals and visitors!

Seth Menser is a gardener at the San Diego Zoo.
Visit our Plants at the Zoo and Wild Animal Park section.
Read Seth’s previous blog, Native Hawaiian Plant Garden.

One great thing about the San Diego Zoo is that we realize that we have the ability to help save and preserve many species that are threatened in their native habitat. A small slice of this can be found at our Hawaiian Native Plant Garden, next to the Lory Loop near koalas, and another patch near the top of Bear Canyon. Some of the more notable species you will find there are the koa tree Acacia koa Loulu palms Prichardia ssp. and the cabbage-on-a-stick plant Brighamia insignis.

The koa tree has been logged extensively for the fine grain wood it produces. Bowls, tables, ukuleles, and many other expensive products are made from it. Hawaii’s only native palm genus, the Pritchardia, is represented here with several species, and the cabbage-on-a-stick plant, extremely rare in the wild, is flourishing at the San Diego Zoo.

These are just a few plants we grow in the Zoo’s Hawaiian Native Plant Garden. There are some that we are unable to grow here in San Diego due to climate differences, but we are always adding new ones and growing species in our greenhouse. For us, it is a thrill to try to create an area in the Zoo that mimics the Hawaiian Islands, right down to the lava rocks!

Seth Menser is a gardener at the San Diego Zoo.

Visit our Plants & Gardens section.