Mark Dimmitt Open House 2024 - Strophocactus, Wittia

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Dr. Mark Dimmitt is the retired Curator of Plants at the Arizona-Sonora Desert Museum in Tucson. He is world famous in succulent growing circles for his Adenium hybrids. These are plants in the oleander family from southern African through the Arabian Peninsula. He is also a master orchid grower, with many AOS awards.

Today he hosted the Tucson Orchid Society and Desert Valley Orchid Society for an open house, inspired because his Dendrobium anosmum are flowering. I've written about those in another thread.

The enormous greenhouse is full of many different kinds of orchids, bromeliads and a few other plants that need to stay warm in winter. I'll show some:

This is the largest Bulbophyllum phalaenopsis I've seen in person. It's not in flower now.



Dr. Dimmitt experiments with growing techniques. Here he mounted a Vanda on used evaporative cooler pads. He said it didn't work well, most likely because of mineral buildup in the pad with use.



Strophocactus wittii (formerly called Selenicereus wittii, and before that Strophocactus wittii) is an Amazonian epiphytic cactus that wraps its flat stem segments around branches as a shingle plant, high in the forest. It is extremely uncommon in cultivation. The flowers open only for one night.



The white spots you see are root primordia. Many epiphytic cacti make roots along the midribs of stems and attach themselves to trees.



He said it is difficult to establish cuttings. They don't adhere well to smooth branches, and rough bark falls off branches with time. He presses cuttings against shingles with some potting soil behind them.



He said they grow well in a standard greenhouse, and don't need extreme humidity. Their environment is very hot and humid all year, though there may be rainless periods for several weeks here and there throughout the year. He water his every time he enters the greenhouse.

Wittia amazonica is another Amazonian epiphytic cactus. (Witt was very active collecting there - lots of things are named after him.) It has the only flowers with blue pigment in the entire family Cactaceae.



The camera doesn't capture the flowers well. The tips are a glowing blue, rather than the purple shown in the photo. This is an easy plant to grow if you can provide a little more humidity than in a typical home, but it is hard to find for sale. It likes an open medium, and staying very moist. It's too large at flowering size for any but a very large terrarium. Dr. Dimmitt's plant had numerous small fruits, which I'd never seen. My plant has never set fruit.