A World Under Glass

Discover plant life from two vastly different environments at the Cleveland Botanical Garden.

By Tom Arbour, Curator of Living Collections

Imagine living in a place for 11 straight months without seeing a drop of rain. What would it feel like? What would you need to survive? Now imagine being stuck in one position without being able to move. There are no permanent rivers, ponds or streams, and it may rain only once or twice a year. These are the desolate environmental conditions that have shaped the plants of the Madagascar spiny forest, a thin band of habitat along the southwest shore of the island located off the southeast coast of Africa. The flora and fauna of Madagascar are so unique, it is often referred to as the world’s eighth continent.

Now, in your mind, fly to University Circle and the Cleveland Botanical Garden. If you’ve never visited, the garden is anchored by the towering Eleanor Armstrong Smith glasshouse, which is divided into two distinct biomes that tell the story of how climate shapes the plants that grow in a place. Step into the main entrance and you will be transported to southwestern Madagascar, the driest part of the mini continent. The towering cliffs represent an oasis at Isalo National Park. Look up and you’ll see tropical looking screw pines (Pandanus spp.) and traveler’s palms (Ravenella spp.) But quickly, you’ll notice rocky outcrops and the scraggly, thorny plants making a hardscrabble life growing in nooks of soil. As you continue, you’ll slowly journey southwest to the coast, reaching the driest part of the continent that is the Madagascar spiny forest.

The spiny forest is well named — many of the plants are covered with very sharp, strong spines that would bloody anyone that tried to venture through. Unlike the tropical Costa Rica glasshouse next door, the Madagascar forest is harsh. Beautiful is a word rarely used to describe it, and some may call it bland and devoid of color at best. Human beings are naturally uncomfortable in this type of environment. But when you visit, please live in that discomfort for a bit and explore your surroundings. Imagine how difficult it is for organic beings to persist in such a harsh, dry place. I guarantee you will find wonder and magic when you stop, think and take in the exotic plants around you.

Despite its dryness, this community isn’t a sparsely vegetated desert. Both in nature and in the glasshouse, the spiny forest is surprisingly full of many rare and unusual plants that have incredible adaptations to help them survive. When it does rain, the plants burst with life, and the glasshouse is surprisingly green and lush in early summer. But in the long interludes without water, adaptive structures like pachycaul trunks, succulent leaves and reduced leaves help the plants stave off desiccation.

Perhaps the most easily spotted tree with a pachycaul (literally “thick stem”) trunk is the Madagascar palm (Pachypodium lamerei). Spines cover every part of the plant except the leaves and flowers. The trunk is noticeably thickened, serving as a reservoir of water during dry times. In the upper reaches, antler-like ascending branches support sizable clusters of white, fragrant flowers — it’s one of the few showy plants in the glasshouse. For most of the year, it is leafless, but it makes up for this by carrying out photosynthesis in its trunk and branches. While called a palm, it’s a member of the dogbane family (Apocynaceae).

Another adaptation to avoid water loss is to have leaves with waxy coatings and thickened, fleshy, water storing tissue. While Aloe vera (a scientific name everyone can learn!) may be a familiar plant, did you know that some Aloes of this forest keep growing upwards and form single-stemmed trees? It’s an excellent specimen of vahombre, the indigenous name for the Madagascar tree aloe (Aloe vaombe), which can be seen near the east wall of the glasshouse, growing up and supported by a Madagascar palm. As it reaches upward, its old leaves senesce but stay attached to the stem, hiding it by a long tower of stacked, withered leaves.

Our final endemic is member of the genus Didierea. Many of these plants have the word “octopus” in their common names because they have large, cactus-like stems that reach up from the ground like massive tentacles. Be on the lookout for the

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octopus plant, Didierea trollii. Its trunk branches into two arms that twist laterally. When growing with other individuals in the wild, the landscape looks somewhat like the twisting necks of the nine-headed hydra of ancient Greece. The Octopus plant has deciduous, reduced leaves that are protected by long, strong and really sharp spines.

These are but three of the nearly 100 plant taxa, many of which are threatened with extinction, that call the glasshouse home. While some like the Madagascar palm are widely available in the horticultural trade, others remain rarely propagated. Unfortunately, Madagascar is one of the least economically developed countries in the world, and the people practice subsistence slash and burn methods, which destroy this rare habitat as it is converted to grazing land.

Holden Forests & Gardens is one of only two organizations in the world that exhibit plants from the Madagascar spiny forest in a glasshouse. While the collection was assembled primarily for educational purposes, there is great potential to acquire additional specimens through collaboration with other gardens so that it can truly serve a conservation purpose. Our advantage is that we house the plants in a climate-controlled glasshouse, allowing us to adapt to a changing climate and manipulate the environment in which they are housed.

I invite you to explore the Madagascar glasshouse during your next visit. The unique shapes, textures and patterns and incredible stories of plant survival from a harsh, faraway land are truly fascinating.