Daryl Venable of
Tezula Plants spoke to the
Desert Valley Orchid Society Thursday, September 20, 2018, on Tolumnia, his specialty. I was trying to find a way to get the images from his computer to our projector, and unfortunately missed a lot of the talk. What follows is the small amount I heard and remembered while fiddling with cables.
As a result of my distraction, it is very possible I introduced errors into what follows. Those are my errors, and not Daryl's. If people who were there correct me I will edit this and update the notes. I added a few of my observations [in brackets like this.]
Daryl's family moved from the Eastern Cape, Republic of South Africa, to the Miami region when he was 19. He had grown many African orchids, but fell in love with Tolumnias. They now are the main thing he grows.
He breeds Tolumnias. He sells his seedlings, and also mericlones. He sends his seed to Thailand for flasking, then re-imports them when large enough. He also imports small mericlones.
The first thing he talked about was air circulation. He said a stiff breeze in the greenhouse is, by far, the most important factor in growing Tolumnias.
They need very good air circulation. He realized this when he visited a master Tolumnia grower, and noticed all the plants' leaves were moving constantly in the very strong wind from many big fans. This kind of air movement cuts down on infections. He has many fans in each greenhouse. He said anybody growing Tolumnias needs to have big, strong fans blowing on their plants.
Tolumnias do better with roots attached to something, rather than loose in the air. He prefers to mount his plants. They can be grown in small clay pots. They can be grown bare-root in these pots, but they do better with tightly packed medium, so they don't move at all. The medium needs to drain rapidly, and provide plenty of air at the roots.
He puts imported seedlings and mericlones bare-root into tiny net pots, and sells them. This is an acceptable short-term solution for growing them, but he would not grow them like this long-term. The plants he keeps for breeding he mounts very firmly on cedar, which lasts the longest among other kinds of wood in humidity. He can't use cork for mounts, because a tiny local beetle destroys it quickly. [He talked about going to a lumberyard for cedar scraps in bulk, but I have found I can buy a 6' / 1.8 meter tall x 6" / 15cm wide cedar fence plank at Home Depot for $3 and cut it up with a hacksaw. I don't have 50,000+ plants like he has.]
If you don't want to mount them, they must be very firmly anchored in the medium, or they will not root and take off growing.
They must be very firmly attached to the mount, with no possibility of motion, or they will not root onto it. Most ties of nylon, cotton or similar will damage the plant if tied tightly enough.
He prefers to use strands of nylon pantyhose to tie the plants. He cuts off the feet and top, rolls the leg section tightly into a donut, then cuts the donut into 1" or 1/2" sections. Then he unrolls these. They are usually much longer than needed, especially because they stretch, so he cuts them down to length. He uses them around the entire base of the plant to attach it firmly. He doesn't take off the pantyhose tie as plants grow; soon it is buried and can't be seen.
He mounts new growth facing the mount wood, not away, so it attaches more firmly to the wood. He thinks this is very important for establishing plants on mounts.
They need lots of sunshine to bloom, but they will burn with too much. If an otherwise healthy plant is not blooming, he recommends giving it more light. Lack of sufficient water makes them more likely to burn in the necessary bright light. He grows under part shade in Florida.
[Here in Arizona they tolerate direct morning summer sun through a window if well-watered. This is far brighter than sun in most other parts of the US and Europe. I don't have a spot with more than 4-5 hours of morning sun, so I haven't tried that, but I suspect full sun all day through a window would be fine, if a fan were on the plants and they had enough water.]
They are drenched in dew almost every night in habitat. Then, they dry within a few hours of sunrise. They need a lot more water than most people realize. After air circulation, this is the most important factor in growing them.
In humid south Florida, south of Miami, he often waters his mounted plants three times a day. Because of his high humidity, he waters so they are dry before 11 am, or he is worried about bacterial and fungal rots. Many are seashore plants, and they don't mind water high in dissolved minerals. Save the reverse osmosis water for other plants.
[In my Phoenix sunroom, with 40%-60% relative humidity, I submerge my plants in water overnight several times a week or they shrivel. In very humid areas this would quickly rot the plants. Growers will need to figure out how to balance their humidity with the plants' requirement for plenty of water and air circulation.]
Mealybug and scale attack is usually first noticed when plants develop an unusual, and characteristic, green "rainbow" look to them. The insects hide in plant crevices. They can be found by gently spreading leaves apart. For small infestations brushing and dish soap solution can be used. For larger problems pesticides are used.
Southern Florida growers have to deal with pests and diseases resistant to a lot of chemicals. They can no longer use Orthene / acephate, nor Merit / imidacloprid, because their scale and mealybugs are fully resistant to them. He mentioned two expensive to supremely expensive insecticides he uses on recommendation from a pesticide expert. [I had never heard of them, and I don't remember them, since I wasn't taking my usual notes.]
Florida has a strain of bacterial genus Erwinia which kills Tolumnias within 24 hours of the first signs, turning the plants to brown mush. This bacterium is still susceptible to Physan-20, but it must be applied instantly when the infection is noticed. He reiterated the best way to prevent diseases is with very high air circulation. [He struggles with very high humidity year round. In my lower humidity I don't have any infection problems.]
That's all I heard. I didn't hear him talk about fertilizing, temperature nor humidity. His humidity is very high all year. [I've been to places where Tolumnias live, and they don't always have super-high humidity. None of them experiences frost in habitat. I have observed they don't mind temperatures all the way down to near freezing, so long as they don't turn to ice. Mine grow very much faster as temperatures rise.]
After the meeting, Darryl told me Oncidiums are relatively unstable in mericloning, and meristems for propagation should only be taken from divisions of the original plant, not from mericlones. He said the Thai firm Jairak is careful about this, so their mericloned plants cost a little more. He buys from Jairak. Other Thai firms mericlone the plants they buy from Jairak, then mericlone those mericlones, then mericlone those mericlones... and sell them into worldwide commerce. Very quickly the mericlones mutate into things that look completely different. He said Tolumnia Snow White has become the poster child for this: It is supposed to be white, but a great many mericlones sold as Snow White bloom pink.
If you like Tolumnia Jairak Flyer 'Corona', buy it quickly, because mericlones no longer seem available!
Daryl Venable on Tolumnia - DVOS September 2018
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