UC Berkeley Botanical Garden: Mexican Collection

Last weekend, I visited the University of California Botanical Garden located on the campus of UC Berkeley to check out their ongoing plant clearance sale. After I had safely stowed my haul in my car, I decided to take a look at the Mexican and Central American collection, skipping my usual haunts, the Southern Africa section and the New World Desert.

The Mexican and Central American collection recreates evergreen cloud forest and pine and oak woodland habitats. Most of it is forested, and lush ferns thrive in moist pockets. I’m not a tree expert, but many rare species of magnolias, pines and spruces are said to grow here. The main attraction for me were the succulents, the majority of which grow in sun-drenched clearings.

Unlike the New World Desert, which looks like a man-made landscape, this section of the Garden has a very naturalistic look. It’s easy to forget that you’re in the Bay Area and not in some remote part of Mexico. The downside, if you can call it that, is that the plants aren’t as “perfect” as they would be in a manicured planting bed. There is leaf litter and tree detritus, and the area has the disheveled look of nature. Some people may find this objectionable, but I actually found it refreshing. Plus, it makes me feel better about all the leaves that are mixed in with my succulents at home.

The very first succulent I spotted was this large Beschorneria albiflora. Like agaves, beschornerias form rosettes but their leaves are soft and unarmed. While most agaves only flower once and then die, beschornerias flower every year. Beschornerias are not very cold-hardy, although the Beschorneria albiflora in our backyard has survived 25°F with no ill effects.

Beschorneria albiflora

Grass trees are always an impressive sight. Australia has its xanthorrhoeas and Mexico has its nolinas. The first one I was simply labeled “ Nolina sp.” but it was beautiful nonetheless.

Grass tree (Nolina species)

Nolina leaves against the sky

Nolina nelsonii, shown in the next photo, forms a perfect head of stiff leaves and eventually a trunk up to 8 ft. tall. At a distance, it looks quite similar to Yucca rostrata (see further down) but its flowers are very different. Nolina nelsonii is hardy to 0°F and deserves to be used more frequently in xeric landscaping schemes.

Yucca faxoniana (left) and Nolina nelsonii (right)

The plant on the left in the photo above is Yucca faxoniana, another supremely architectural species in what has got to be the most underappreciated genus in the succulent world. Just take a look at these magnificent leaves adorned with curly threads. This is a large plant, up to 15 ft. tall. While not as über-hardy as some of the other yucca species, it still tolerates temperatures down to 0°F.

Yucca faxoniana

I’ve raved about Yucca rostrata before (1 2 3 4), and I was happy to come across another magnificent specimen in this section of the Garden. (If you’ve been to UCBG, you’ve seen the spectacular Yucca rostrata just outside the main entrance.) I can’t wait for my own specimens to look like that. It might be another 20 years, considering how slowly this species grows.

Yucca rostrata (background)
and Agave scabra (foreground)

Seen in the photo above and below, Agave scabra is a fairly large species (4-6 ft. across) with gray-green leaves sporting serrated edges. It is abundant in the Chihuahuan desert (northeastern Mexico into south Texas) where it grows at altitudes from 3,600-5,700 ft..

Agave scabra

Agave chiapensis is a medium-sized (2-3 ft. across) species that freely offsets, eventually forming large clusters. As its species name suggests, it is native to Chiapas, Mexico’s southernmost state, and hence fairly intolerant of cold. It will take a few degrees below freezing, but gets damaged below 25°F.

Agave chiapensis

Agave montana grows high in the mountains of northeastern Mexico and is tolerant of cold (10°F), drought and poor soil. It has the potential to grow to 6 ft. across but in cultivation it will most likely stay smaller. It has apple-green leaves (actually quite similar to Agave chiapensis above) with large teeth and a pronounced terminal spine. I love this agave and don’t know why it isn’t more popular. (A tissue-cultured selection called ‘Baccarat’ is sold in specialty nurseries.)

Agave montana

Agave filifera (seen on the left in the next photo) is the archetypical thread-leaf agave. It forms rosettes to 2 ft. across and can easily be recognized by the many curly threads along the leaf margins. I have a subspecies called Agave filifera ssp. schidigera, which I bought several years ago at UCBS’s Landscape Cacti and Succulent Nursery (open to the public for plant sales every Thursday from 10:30am to 1:00pm). It looks just like Agave filifera but has slightly wider leaves.

Agave filifera (left) and Agave montana (right)

Agave striata is widely available in nurseries, even in box-store garden centers. Strangely enough, I do not have this species in my collection, but will remedy that soon. It’s a small species, usually no more than a foot across, but it suckers prolifically, forming large colonies. It is one of the few agaves that are polycarpic, i.e. they do not die after flowering. It tolerates temperatures in the mid-20s.

Hedgehog agave (Agave striata)

While many agave species are unique and don’t interbreed, others do, resulting in hybrids that are difficult to place taxonomically. Several at UCBG were labeled “Agave sp.,” meaning that even the experts don’t really know what species they are. As is the case with dogs, mongrels are often surprisingly beautiful, and these agaves are no exception.

Unidentified agave species or hybrid

Giant agave flower stalk

Unidentified agave in a sea of penstemon

In one particularly sunny corner of the Mexican Collection, I came across two species of Graptopetalum, a prolifically offsetting groundcover succulent. Graptopetalum goldii is a new species to me; I love how its bright green leaves contrast with the purplish echeveria rosettes next to it.

Unidentified echeveria species (left) and Graptopetalum goldii (right)

Graptopetalum amethystinum, aptly named “lavender pebbles” in common parlance, looks quite alien to gardeners unaccustomed to succulents. Last year, I bought a specimen labeled Graptopetalum amethystinum, and it’s turned into a large solitary rosette. I wish it would produce some babies so I have some to plant in other places.

Graptopetalum amethystinum

After photographing many of the cycads at UCBG last December, I’ve been on a cycad kick. I ordered a few small ones and have been reading up on these living fossils. I was ecstatic when I encountered quite a few dioons growing in the Mexican Collection.

Dioon is a Mexican cycad genus that does particularly well in our climate. Dioon edule is the most common species. It tolerates cold (down to the mid-20s), heat, drought and poor soil with aplomb and, next to the sago palm (Cycas revoluta), it’s one of the cheapest cycads to buy. There are several subspecies, some with significantly bluer leaves, but the ones at UCBG looked pretty much like the species.

Yucca faxoniana and Dioon edule

Dioon edule

Dioon edule cone

Dioon edule (background) and Muhlenbergia dumia (foreground)

Dioon edule (foreground) and Muhlenbergia dumia (background)

I’m so enamored with Dioon edule that I just bought three seedlings on eBay. Stay tuned for a separate post.

NOTE: Most of the photos in this post were taken either in full sun or in dappled light. I would have preferred a nice overcast day but the weather wasn’t on my side. I plan on going back in the summer when, oddly enough, the weather in the Bay Area is often overcast.