Oncidium alexandrae is an enchanting orchid known for its spray of yellow and brownish-red flowers that resemble a cloud of butterflies. Its slender, arching stems and glossy green leaves allow it to thrive in the dappled light of its native forest canopy. The striking contrast of its blossoms, coupled with the plant’s graceful poise, makes it a captivating specimen in the orchid family.
I. Appearance and Characteristics
Oncidium alexandrae, synonyms including Odontoglossum crispum, is an epiphytic orchid in the genus Oncidium.
Oncidium alexandrae is found in the montane forest of Colombia, at altitudes of between 1,800 metres (6,000 ft) and 3,000 metres (10,000 ft), including in the eastern Cordillera in the departments of Cundinamarca and Boyacá and in the Andes of southern Colombia in the departments of Cauca, Putumayato and Nariño.
The plants grow as epiphytes in clearings and along forest edges. They grow chiefly on the trunks and main branches of oak trees in partial shade and occasionally full sun.
Throughout the year, days average 19–21 °C (66–70 °F) and nights average 10–12 °C (50–54 °F), with a diurnal range of 9–11 °C (16–20 °F). Rainfall is light to moderate throughout the year, but there is no actual dry season. In addition, more moisture is available from heavy dew and mist. Humidity is 70–75% throughout the year.
Motohiro Sunouchi
CC BY 2.0
Oncidium alexandrae comes in an array of shapes, colours, and shades, from pure white to flush pink. The variability of the flower is associated with discrete areas; in the Pacho area (30 miles north of Bogota) are found the finest varieties, full round pure white and spotted flowers with broad overlapping sepals and petals; in the Vélez area (further north) the flowers are similar but shaded rose; south of Bogota, in the Fusagasugá region (25 miles south of Bogota), the white mauve tinted stellate flowers; while in Nariño, a variant is found which bears up to 80 small flowers on a branched inflorescence.
Oncidium alexandrae has an ovoid pseudobulb, between 8 and 10 cm (3 and 4 in) long, from the apex of which emerge two soft-textured, erect to arching, linear to strap shaped or lanceolate leaves. The leaves are sharply pointed at the tip and narrowed below where they are longitudinally folded along the mid-vein at the base to form a long, narrow, petiole-like stem.
The gracefully arching flower spike, which can be up to 51 cm (20 in) long, emerges from the base of a recently matured pseudobulb along the centre-line of the upper basal sheath. Flowers are closely spaced in a raceme on the upper part of the flower spike, but there are often two or three lateral branches at the base of the raceme. Each flower is carried on a pedicellate ovary that is up to 23 mm (0.9 in) long.
There are between 6 and 24 flowers on each inflorescence. The blossoms are the most variable in the genus in terms of size, colour and degree of crimping along the segment margins. The flowers are mostly white or pale rose, sometimes more or less spotted and blotched with brownish or reddish brown. The callus at the base of the lip is yellow and is often marked with red lines. The widely spread, flat-opening flowers are 8 to 10 cm (3 to 4 in) across with very wide sepals that are elliptic, have sharply pointed tips, often overlap and are variously crisped or wavy-margined or toothed and notched along the margins.
The dorsal sepal is lanceolate to egg-shaped, undulate on the margin and 30 to 51 mm (1.2 to 2.0 in) long by 13 to 23 mm (0.5 to 0.9 in) wide. The obliquely spreading lateral sepals are similar in size to the dorsal sepal. The horizontally spreading petals are egg-shaped to elliptic or oblong elliptic, 30 to 46 mm (1.2 to 1.8 in) long by 18 to 38 mm (0.7 to 1.5 in) wide, and have margins that are wavy and fairly deeply notched or toothed.
The lip is oblong or somewhat fiddle-shaped. It is 20 to 30 mm (0.8 to 1.2 in) long by 13 to 15 mm (0.5 to 0.6 in) wide, has toothed margins and is rather sharply pointed at the apex. The callus is fleshy with a pair of diverging lobes at the apex. The slender, slightly arching column is 15 to 18 mm (0.6 to 0.7 in) long and has a pair of broad wings with fringed margins toward the apex.
II. How to Grow and Care
Sunlight
Odontoglossum crispum loves the bright sun without access to direct sunlight, so during the midday it must be put behind a curtain or into the shade of other plants.
Temperature
This orchid belongs to a moderately cold temperature regime: Summer temperature at 16-24 ° C; Winter temperature at 7-18 ° C. The ideal temperature for growing is 7-16 ° C. To successfully grow this species, the night temperature should always be at least 3 ° C lower than the daytime temperature.
Humidity
The Curled Odontoglossum needs relatively high humidity. The minimum indicator should be at least 70%. If, however, it is impossible to avoid exposure to high temperatures, the humidity of the air must be increased together with the temperature. This will help the plant better survive the forced heat. The humidity of the air must be at least 80-90%.
Watering
During the period of new growth this orchid needs frequent and abundant watering. Excess water during watering should flow freely out of the pot, as the stagnation of water both inside the pot and in its pan can very quickly lead to decay of the roots and the lower part of the plant. The substrate between waterings should dry well.
In hot summer days when finding orchids outdoors, regular spraying of the outer part of the plant is recommended. This will help the orchid to better tolerate the forced heat. At home, spraying does more harm than good, as it creates favorable conditions for the development of various kinds of fungal diseases , so it is strongly recommended to abandon it.
Soil
The “soil” required for oncidium alexandrae is special because, as an epiphyte, it originally grew on big trees in tropical forests. You need to mimic this growing environment with, for example, water moss, wood chips, coconut shells, volcanic stones, or perlite as soil substrate. You can also buy orchid-specific soil directly from gardening stores.
Fertilizing
During the period of new growth, this type of orchid is fertilized once every 2-3 weeks in 1/4 of the fertilizer concentration indicated on the package. Too concentrated fertilizer adversely affects the roots of Odontoglossum crispum, they turn black, become slimy and die.
For the prevention of salinization of the substrate, it is strongly recommended to rinsed it well every six months. To do this, the pot with the orchid should be placed under a stream of warm water and several times well rinsed.
Planting Instructions
You do not need a large pot to grow an oncidium alexandrae as it won’t produce a vigorous root system that occupies much space. If the pot is too large, the soil tends to collect water and cause root rot. The height of the pot should be 2.5 cm taller than the (pseudo)bulb of the oncidium alexandrae. You can easily buy oncidium alexandrae in a local gardening store and simply place it in breathable, well-drained substrate. After planting, use upright sticks to support flowering branches. In warm, humid climates, cover the root of oncidium alexandrae with sphagnum moss and attach them to a tree with strings.
Pruning
It is best to prune wilted oncidium alexandrae flowers promptly after blooming to reduce unnecessary nutrient consumption and promote more blooms. Trim withered and diseased leaves promptly to increase air circulation, thus reducing pests and diseases.
Propagation
You can propagate oncidium alexandrae by division or by cuttings.
Propagation by division: using an oncidium alexandrae with more stems is a better option for the division. You should do this after blooming. When dividing the plant, dig it up carefully with its roots intact, and cut the roots into several clusters from the base. Remember to use clean tools and disinfect the wounds with a fungicide. Then plant your divided clusters in containers and keep them in a cool place. While the new roots are growing, spray them with plenty of water to prevent them from drying out.
Propagate by cuttings before flowering. Choose a healthy, thick stem, remove the leaves, and cut it into small 2-node pieces. Insert the bottom directly into the substrate. Keep the substrate moist, and they will root and sprout in about 2-3 months. You can also propagate by cuttings by laying the entire stem on top of moist substrate, and cutting it into pieces after it roots and sprouts. Transplant those rooted cuttings into pots for further growth. A third way to propagate by cutting is possible during weather with high temperatures, when the stems develop roots, and you can cut them off and plant them.
Rest period
To stimulate flowering Odontoglossum crispum needs a clearly defined period of rest. It begins immediately after the maturation of new bulbs, i.e. when new young shoots reach the size of the old, and is that the orchids contain much drier and colder than usual, and do not fertilize. The temperature during this period should be at night about 13-14 ° C, and in the daytime no more than 16 ° C.
Watering the orchids significantly reduces, but does not stop completely. Water should be small every two weeks. It is highly recommended not to allow the pseudobulb of the plant to shrink too much, it may adversely affect its further well-being. After the appearance of peduncles, the rest period ends: irrigation resumes in the usual volume, and the overall temperature of the content rises.
III. Harvesting and Storage
If you want to display oncidium alexandrae flowers in vases, harvest there are only 2-3 flowers blooming on the stem. Cut diagonally at the bottom of the flower stem, and place it in a vase immediately. You can enjoy the cut flower in clean water for about 14 days, or for a longer time with preservatives.
