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Desert-adapted Orchid, Etc.

It was a lovely day for a cycle ride in May. I was happy to be able to cycle to volunteer for a few hours at the Conservatory Greenhouse on the U of M's St. Paul campus. There, I was allowed to pick chores from a list written on a white board in the head house, or control room of the Conservatory. Among the tasks were vine maintenance and pest contol - with and without chemicals. Along the way I saw lovely and amazing orchids in full bloom. 

Desert-adapted orchid

When I think of orchids the image I have in my head is that of an epiphytic plant clinging to the branch of a tree in a damp jungle. But I was surprised to discover the existance of an orchid growing in the rocky granite soil of the desert room. The plant is native to Kenya and South Africa where it grows in full sun on rocky outcropings. The leaves are stiff and spiky like an aloe plant. The flower spikes can be up to 2 meters tall; I suspect height is so that pollinators can locate them in the rocky environment where they evolved.

I noticed the presence of this plant in the desert room last year as I was cleaning dead leaves and debris from the beds. I have been waiting until today to see the plant in full bloom. It was exciting to see it finally happen!

Relevant to the desert orchid are a few factoids from the web site of Kew Gardens:
- There are 28,000 species of orchids, divided into 850 genera
- Orchids are found in every climate zone, on every continent; even above the Arctic Circle
- There are more species of orchids than there are of living bird species

Eulophia petersii

Spiky leaves of the desert-adapted orchid, Eulophia petersii

Tulip orchid

Equally stunning for its shape and color is the tulip orchid, now if full bloom. This plant is native to the forest floor at high elevations in South America; think of the high Andes Mountains. It is interesting that actual tulip plants are also native to cool mountainous elevations, but of the Middle East not the Andes. Could this be an example of convergent evolution, where two unrelated plants evolve to appear similar to each other? They are both adapted to similar conditions, the shape of the flower must give them some advantage over other flower shapes. Perhaps the flower provides a sheltered microenvironment which a pollinator would find attractive in addition to the color of the petals.

Tulip orchid, Anguloa dubia, South America

Tulip orchid, Anguloa dubia

Vine maintenance

Today I chose to do one of the chores I frequently return to - the pruning of vines as they overgrow their little spots on the vine bench. Each vine plant given an overhead steel cable which they use for support. But some plants grow faster than others and - over time - are capable of completely overwhelming a slow-growing neighbor. Occasionally, the vigorous plants need pruning back to keep them all in line. 

Several vines, now disentangled

Pest control with essentail oils

Another recurring chore in the greenhouse is to keep the insect pest population under control. Today I used a commercial product, a mixture of essential oils, to spray on the leaves of plants to reduce the population of thrips insects. The dilute mixture of peppermint and clove oil is noxious to many of the pests in the greenhouse. It has the benefit of being non-toxic to people and plants. 

I was assigned to treat a bench of tropical plants - mainly cycads and zamia plants - with the essential oil solution. Every plant on the bench was sprayed using a hand-spray bottle, the plants were then doused with a sharp mist to drive off any clinging pests.

Cycad and zamia bench in the tropical collection room,

Sharp spray from a hose

In addition to non-toxic chemicals, some plants are treated with plain tap water to blast insects off from leaves which have grown to be out of reach by hand. In the photo I've used a ladder to get as high as I could to pelt the little critters with a strong spray of water.

Pest control, using a ladder and the jet setting



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