Oncidium Alliance orchids are orchids, belonging to Oncidinae subtribe of tribe Cymbidinae. They are tropical sympodial orchids, belonging to the Ada, Brassia, Gomesa, Ionopsis, Macradenia, Macrochilus, Macroclinium, Mexicoa, Miltonia, Miltoniopsis, Odontoglossum, Oncidium, Osmoglossum, Otoglossum, Plectrophora, Polyotidium, Psychopsiella, Psychopsis, Psygmorchis, Pterostemma, Tolumnia, Zelencoa and some not so famous genera. They are mostly epiphytes, lithophytes and occasionally terrestrial orchids of varying size – from tiny “dancing doll orchids” Tolumnia species to gigantic Oncidium sphacelatum. They grow in tropical rainforests, mountain cloud forests, some of them even grow in the deserts on cacti (Zelencoa onusta is famous for it). Mostly they bear round shaped pseudobulbs, but Tolumnia and Ionopsis species bear tiny barely visible pseudobulbs, but have thick succulent leaves arranged to fan-shaped leaf rosettes. Some species such as Zelencoa onusta, Psychopsis have green leaves and pseudobulbs, covered with red spots, and even without flowers, they are rather decorative. They mostly have round flowers with a profound lip of bright colors (yellow, red, pink, orange, brown, green, white with different patterns).
The classical “Oncidium flowers” resemble dancing doll dresses. But some species have rather alien-looking flowers. For instance, Brassia species bear spider-looking flowers (because they are pollinated by spider wasps, who mistake them for actual spiders) and Psychopsis blooms with butterfly-looking flowers, which even have something resembling butterfly head and eyes. Very lovely Miltonia species bloom with Pansy-looking flowers (that is why they often called Pansy Orchids). And many Oncidium Alliance orchids are prized for their beautiful flower aromas. Vanilla, chocolate, perfume, confectionary are only a small part of their aroma spectrum.
Most Oncidium orchids for sale at local floral shops are hybrids such as Oncidium Sweet Sugar, Oncidium Rosea Sunset, Oncidium Sharry Baby, lovely tiny Ocidium Twinkle with beautiful fragrant flowers. They are lovely, easy and free-flowering orchids which require warm temperatures, some sun, moderate watering and fertilizing when they are at an active growth stage. Some species of Oncidium are also quite easy to grow. Such species as Oncidium fuscopetalum, Oncidium baueri, Oncidium flexuosum, Oncidium dactyliferum, Oncidium cebolleta need warm temperatures, bright light with some sun, watering after substrate drying, and occasionaly fertilizers at growth period. They have insignificant dormancy after flowering, so it is good to reduce watering a little, do not use fertilizers and wait for a new growth. But some cool and intermediate Oncidiums such as Oncidium chapadense, Oncidium auricular, Oncidium olivaceum, Oncidium pergameneum, Oncidium picturatum have some differences in their growing as they demand cool temperatures, so they could not be recommended for novice at orchid growing. There is a group within Oncidium genus so-called mull-eared Oncidiums such as Oncidium splendidum, Oncidium nanum. They have specific growth habit and they thrive if they are planted in a basket or mounted on slabs, as they prefer more dry growing conditions. So, if you ask about Oncidium orchid care, there is no general instruction, as Oncidium is a very diverse genus.
Miltonia and Miltoniopsis orchids
Often seen Miltonia orchids at shops are actually Miltoniopsis hybrids (so called Pansy Orchids). Miltoniopsis orchids (both species and hybrids) are splendid and beautiful orchids with pale green leaves and lovely Pansy-shaped fragrant flowers. They grow in mountain cloud forests at high elevations, so they are particularly hard to grow. They need cool to intermediate temperatures, they die both from overwatering and from insufficient watering, and even one drop of water between their dense foliage could kill the plant, because it may cause rotting. On the contrary, Miltonia species and hybrids, particularly Miltonia spectabilis, are hot to warm orchids, they are tolerant to dry between watering and they are much easier to grow.
Odontoglossum orchids, such as Odontoglossum grande, Odontoglossum crispum, Odontoglossum juninense, Odontoglossum nobile, Odontoglossum wyattianum and others are outstanding orchids, but also not for beginners. They grow at mountains, so they need cool to cold temperatures, careful watering and supplementing with fertilizers. The major problem with Odontoglossum is overwatering (as they are prone to root loss) and high summer temperatures. Temperatures above intermediate level suppress their metabolism, adapted to cool mountain conditions, so their growth is depressed, they become less resistant to diseases and suddenly die. So, if you could not provide orchids with such requirements it is better to choose easier and more ready to flower orchid plants such as intergeneric hybrids, Oncidiums and so on.
There is a very big and diverse group of Oncidium Alliance intergeneric hybrids – so called Cambria orchids. They are called Cambria because of one of the most popular hybrids Vuylstekeara Cambria Plush (Cochlioda x Miltonia x Odontoglossum). Given the fact that they have barely pronounceable in most languages grex names, they are colloquially called Cambria for marketing reasons. What’s about Cambria orchid care? Assuming that most of their ancestry are cool to intermediate orchids, such hybrids also grow best within intermediate temperatures with moderate sunlight, watering after the substrate is dry and occasional feedings with balanced fertilizers when they actively grow. They are particularly easy to care (easier then Odontoglossum but more complicated than Oncidium hybrids) and can bloom up to four times per a year as they have no obvious dormancy. You just need slightly decrease watering after flowering and resume at a normal rate after new growth is seen.
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