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Photo copyright Charles M. Fitch

Miltoniopsis vexillaria 'Fusa', AM/AOS
Grower: L. B. Kuhn
Photographer: Charles M. Fitch

Colombian-Type Miltonia (Miltoniopsis) Culture

NED NASH - American Orchid Society BULLETIN May 1980

 

IN ORCHIDS, as in fashion, styles seem to come and go. A particular hybrid type that may have been relatively commonplace at one time may be virtually extinct at another, with little or no active hybridizing being done. One genus that fits nicely into this group is the Colombian, pansy-type miltonia. These have recently been reclassified as Milioniopsis (Sweet, Amer. Orchid Soc. Bull. 47(10): 917-925) although they will be known as miltonias by most of us for years to come.

In the past, miltoniopsis were extremely popular with growers. Orchid literature from the late 1800's well into the early part of this century is filled with drawings and photographs of magnificently grown plants covered with flowers. It is hard to understand why these lovely orchids passed from favor with most growers, but pass they did. For whatever reason, their decline in popularity came to be associated with a reputation for being difficult to grow. While miltoniopsis are not among the easiest of orchids, the difficulties they pose can be readily overcome.

Photo courtesy of the American Orchid Society

Miltoniopsis vexillaria 'Carolina', AM/AOS
Grower: Roberto Posada Medellin, Colombia

 

At Armacost & Royston (now no longer in business), we grew a large population of seedlings from one of the finest miltoniopsis collections in the world. We, and many visitors to our nursery, have been pleasantly surprised by their vigor and relative ease of culture. They grow like weeds, and a significant number have actually flowered in flats. The following observations are based on our experience at the nursery on a large-scale commercial level, and on this writer's experience at home on the hobbyist level.

Many people have been frightened away from these rewarding orchids by a disastrous first experience of their own, or that of a friend (or a friend's friend). These people will hopefully try again because of the increasing availability of high-quality seedlings. Most people have killed at least a few plants, especially when first starting out. This does not scare most away from orchids in general; indeed, it heightens the challenge and excitement of the hobby. Why then should the undeserved reputation of miltoniopsis prevent people from growing and flowering these lovely orchids? Hopefully, this belief that miltoniopsis are tricky to grow will soon be dispelled as a myth without foundation. The beauty of a well-flowered miltoniopsis is well worth the little extra effort that is required. We like to think that miltoniopsis are not difficult, just different.

Photo courtesy of the American Orchid Society
Miltoniopsis Grin 'Billie Fae', CCM/AOS
Grower: Billie and Joe Henriksen, Napa, CA

Miltoniopsis need good light to grow and flower well. The limiting factor is, as with most orchids, minimizing temperature at the desired light level. These are not "under-the-bench" plants: they require more light than a green-leaf paph, about the same light as for the warmer-growing, mottled-leaf paphs - but not as bright as the typical cattleya house. We feel that around 900-1000 footcandles is about right for these plants. Miltoniopsis normally have light green, erect foliage; one needn't worry if the plants look slightly "bleached", as this is their normal color.

Many people have the impression that miltoniopsis are "cool-growing" orchids, like their cousins the Odontoglossum crispum types. While miltoniopsis certainly will not tolerate the extremes of temperature that a cattleya or vanda might, they by no means require - or like the almost frosty treatment in which most "odonts" delight. Night temperature is not a critical factor in our experience, as we have grown our miltoniopsis with both paphs (55-58F nights) and phalaenopsis (65-68F nights) with good success. Night temperature should be kept at or below the high range, however, for best growth. Miltoniopsis will tolerate down to 50F at night if kept on the dry side (but not bone dry!). Young seedlings will, of course, prefer the warmer range of night temperature while mature plants should be run at 58-62F nights.

Photo courtesy of the American Orchid Society
Miltoniopsis Mount Mazama 'Crater Lake', AM/AOS
Grower: Ronald Sellon, Oregon City, OR

The day temperature seems to be the critical factor for miltoniopsis. As discussed earlier, miltoniopsis like good light, but the temperature should be kept to a 80-85F maximum whenever possible. Miltoniopsis can be considered "moderate" growers, temperature-wise, because they prefer not to be subjected to extremes. As with most orchids, increasing relative humidity with increasing light and temperature factors will help to keep the plants from becoming over-stressed. We feel that 50-70% relative humidity is good for miltoniopsis.

Today, most greenhouses in warm-climate areas have some type of cooling system. The most common type is evaporative cooling, whether from a "swamp" cooler or a pad and fan system. These are useful for more than just maintaining a reasonable temperature level, as they increase air movement and humidity in the process of cooling. In warmer areas, miltoniopsis would appreciate being placed near the outlets of your cooler, or near the pad end if that system is used.

Photo courtesy of the American Orchid Society
Miltoniopsis Delicious 'Rogue Valley', AM/AOS
Grower: Fred Lofland Central Point, OR

 


Here in Carpinteria, California as opposed to most other parts of the country, these more complex temperature control methods are not necessary. In moderate (usually coastal) areas, the ocean provides a wonderful, natural cooling system. Temperatures here rarely rise above or fall below the prescribed limits for miltoniopsis. Occasionally we will have a Santana wind condition (an extremely hot and dry wind which blows from the east off the desert) and the temperature will hover near the 100F point for up to a week with commensurately low humidity. Even these extreme conditions (we do not have any cooling systems at the nursery) have failed to do more than minor damage to our Miltoma seedlings and plants. This, we hope, will encourage folks in more extreme climate areas - these plants may be tougher than is generally supposed.

Perhaps the most important safeguard against heat-induced damage to your plants is a healthy root system. Miltoniopsis will emerge from a hot spell with much more grace if they have enjoyed good culture all along. A good-sized, well-established plant may look slightly "raggedy" at summer's end, but will bounce back well at the onset of cooler fall weather. One of the necessities for a healthy root system is proper watering. Miltoniopsis, because of their relatively fine roots, like to be "evenly moist." This is an extremely difficult concept for most people. In general, evenly moist means that if one feels that a plant will be dry tomorrow, it should be watered today. Although miltoniopsis enjoy liberal watering, this must be in conjunction with an open mix, as a constantly wet mix will rot the roots. Conversely, if this well-drained mix is allowed accidentally to remain dry for too long, not only will the roots die, but the mix will be quite difficult to re-wet. During warmer weather, a well-established plant will be difficult to over-water. A miltoniopsis' rather thin foliage requires quite a bit of water, and if the mix is well-drained, the plant will use water at an astonishing rate. Horizontally creased or "accordioned" leaves are an indicator of under-watering . The only time a miltoniopsis should be allowed to run on the dry side is directly after potting before root growth commences. As the roots begin to push into the fresh medium, watering frequency should be increased to the normal schedule.

Photo courtesy of the American Orchid Society
Miltoniopsis Marie Riopelle 'McElderry', AM/AOS
Grower: James Riopelle, Portland, OR

Because miltoniopsis require quite a bit of water, and because they resent "wet feet," their mix must be well-drained but water-retentive. This, in most cases, means fine (preferably sifted) fir bark, plus additives to enhance drainage. We use a mixture of fine fir bark, redwood fiber and approximately 10% charcoal for sweetness. This mix is easily produced, inexpensive and very practical for large-scale commercial use, such as in our case. Many hobbyists, this writer included, prefer a mix of sifted, fine fir bark and approximately 15-20% perlite or sponge-rock. For the largest plants, approximately 10% medium fir bark may be added as well. An important point to remember about mix is that overall culture is more vital than the unique composition of a particular mix. In other words, the world's best set of ingredients won't guarantee success. Success with miltoniopsis can only be attained through proper attention to the plants as they grow.

We have found that the single most beneficial cultural technique for miltoniopsis, given all of the above requirements, is annual repotting, preferably during the cooler months. This does not mean, in most cases, "potting-on" into a larger pot, but mainly replacing the used-up mix with fresh. Miltoniopsis will tend to make up two sets of growths during the year: spring-summer and fall-winter. If potted in the fall, when the new growths are approximately 2" tall, the plant will have maximum time to reestablish before the onset of warm weather. Annual repotting in this cycle does not noticeably set the plant back, and enables it to maintain a large and healthy root system in fresh mix. Also, since it is very important never to over-pot a miltoniopsis, pot size may be more closely monitored.

Photo courtesy of the American Orchid Society
Miltoniopsis Darkness 'Red Gable', AM/AOS
Grower: Mildred Munday Redwood City, CA

Miltoniopsis, like most orchids, do their best if allowed to grow into good-sized clumps. Because of their close, compact growth habit, a very satisfactory plant can be grown in a 4" or 5" pot. A small pot in relation to plant size helps to allow the liberal watering the plants enjoy without the consequences of a soggy, sodden mix. A 3-5 bulb division should be considered minimum acceptable size. A larger plant reestablishes more easily, grows and flowers better and is more resistant to adverse climatic and cultural conditions.

We fertilize our miltoniopsis along with the rest of our stock. The plants are fed at weekly intervals at half strength, or the equivalent of a 1/2 tsp/gallon of our 30-10-10 feed. Every third or fourth feeding we use our 6-30-30 formula; this helps the plants to flower better and hardens them slightly. For home growing we recommend biweekly feeding at slightly less than full strength (1 tsp/gal) on the same alternating formula schedule (3:1). If you wish to fertilize weekly, do so at half strength and remember to leach thoroughly to avoid harmful salt accumulation.

Miltoniopsis are susceptible to the same types of pests as most orchids, these being mainly sucking insects. Modern insecticides, such as malathion, will take care of these problems quite well. It is, however, necessary to use extra caution when treating miltoniopsis with oil-based (emulsifiable) insecticides because their thin, tender foliage is more susceptible than most to burning. It is best to treat these plants, when spraying for pests, in the cool of the day as this will help prevent foliar burn from the oil carrier.

Fungal or bacterial rot can be a problem with miltoniopsis, although usually only when the plants have been allowed to run down because of poor cultural techniques. These could include over-fertilizing, over-watering or excessive humidity. We generally do not use, or recommend, fungicides or bactericides in any but the most extreme cases, as the cure is often harsher than the symptom. A plant that is heavily laden with rot is often best simply thrown away unless, of course, it is particularly good or valuable. Any rotting plant is a potential source of infection for the rest of the collection. The best cure for rot is to remove the problem area with a sharp, sterile knife. The area should be left exposed to the air. Most rots are anaerobic, meaning that they exist where there is little or no oxygen. Admitting fresh, dry air to the infected area will allow the plant's natural defenses to act. The best preventative to rot problems is good overall cultural practice.

Photo courtesy of the American Orchid Society
Miltoniopsis Storm 'Floval', AM/AOS
Grower: The Beall Company Vashon, WA

If all has gone reasonably well, you will see flower spikes emerging from the basal leaf-axils of the newly matured bulb(s). Flowers will tend to be at their best during the cool season; these will most often come from the bulbs initiated in the fall and matured in the winter. Summer flowers will generally be smaller and of weaker color. One or two spikes per bulb is the general rule. The number of flowers per spike depends on type and breeding, as does flower size to an extent.

We hope the foregoing information drawn from our experience proves of some value in helping people toward success with these lovely plants. As with any cultural article, these observations should not be accepted as "words of God" or the be-all and end-all of miltoniopsis culture. Rather, they should be accepted into one's "data bank" and used experimentally at first. In this way, the information can be tested and the value judged on its usefulness to the individual, who knows best his own environmental situation. - P. 0. Box 385, Carpinteria, California 93013.