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Orchid Maintenance Up in the Rafters

Many species of orchids are epiphytic, meaning the live up in the trees. The University of Minnesota Conservatory greenhouse has one remarkable example of an orchid in this sort of habitat. This particular vanda orchid has lived for many years in a 3 x 3 ft wooden basket. In 2019 the plant was moved from the old greenhouse and hoisted up into the rafters of the tropical room of the new greenhouse. It has continued to grow to weight of approximately 50 lbs. The orchid has several branches growing out from the root ball, each branch measuring up to 3 feet in length.

After so many years of growth, the root ball has begun to rot and collapse. Today's chore was to help the greenhouse staff to assemble ladders and gather equipment to remove the old orchid and replace it with cuttings from the old plant, now in a new basket.

As the staff cut apart the old orchid, large sections of the orchid fell to the floor. The cuttings were free for the taking since they were to be disposed of in the organic waste pile. But, the cuttings came with a warning: the orchid was infected with an orchid virus. Any tool used on the plant was likely to infect any other orchid plant if the tool was not properly disinfected.

Plants, much like people and animals, suffer from a variety of infectious bacteria and viruses. Orchids are a host to more than 50 different types of viruses. The two most common are cymbidium mosaic virus and odontoglossum ringspot virus. These two are major sources of plant loss for orchid growers. Once infected, the virus spreads to all parts of the orchid plant. They are specific to orchids and do not infect other plant species. The signs of infection are yellow, brown, and sunken coin lesions on leaves and blossoms. Once infected, the virus cannot be removed from the plant. Not all infected plants will show active lesions, depending on the variety and health of the orchid plant. Prevention is limited to ensuring tools are properly cleaned before and after use.

Orchid cuttings in a new basket; the strap-like leaves of the vanda orchid are just barely visible at the edge of the basket. Arching over the basket are branches of a fig tree.

After helping with the orchid, I chose another chore from a list of tasks. There are four different display rooms open to the public (another four rooms are not open to the public without supervision). Each room represents a particular climate biome. Since they are frequently seen my the public, I chose to clean plant debris and weeds from the gravel beds in two of the four public display rooms. As I worked, I attempted to answer visitor's questions about plants in the collection.

Now clean gravel bed in the Mediterranean scrubland room

I'm always on the lookout for plants new to me. I noticed this bright red bell-shaped flower of wooly kohleria (Kohleria hirsuta var. hirsuta). The plant is native to South America and the Caribbean Islands. It is used to a warm dry habitat and prefers to scramble over rocky well-drained ground. I suspect the fine hairs help gather moisture and perhaps protect from insects.

Wooly kohleria (Kohleria hirsuta var. hirsuta); native to South America and the Caribbean Islands. Note the fine hairs on the leaves and flower edges.

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