Updated: Mar 6, 2020
The group of orchids now called Tolumnia were at one time called Oncidium section Variegata or commonly referred to as "equitant oncidiums". The foliage seldom exceeds 6 to 8 inches in height, and a 4-inch pot can house a "specimen" plant. The leaves are arranged in pairs overlapping or straddling one another at the base, accounting for the popular term "Equitant". Flowers are produced primarily in the spring on 12- to 18-inch inflorescences that are often branched on older plants. Some types have much shorter, bouquet-like displays.
The key to growing Tolumnias is understanding their natural habitat. The species are endemic to the Central America and Caribbean Island Basin with many confined to a single island. Most of the species involved in modern hybrids are found in intermediate to warm conditions growing on twigs where they are exposed to bright light and air movement. Moisture is provided by high humidity and by daily rain showers. Due to constant air movement by the trade winds, plants never remain wet for long.
These plants can often bloom more than once a year. Larger specimen plants or large collections of Equitants can provide some blooms most of the year round. Today's hybrids offer an astounding array of colors and patterns not seen in the species. Their petite size and ability to adapt to a fairly wide range of conditions make them suitable for growing spaces under lights or on windowsills.
Tolumnia orchid loves bright sunlight and is able to tolerate direct morning and evening sun, however, in the hot summer noon especially in the windows of southern orientation, the orchid should be protected from direct sunlight. They do well growing in an east window receiving sunlight from early in the morning until 11:00 or 11:30 AM. Put behind a curtain for example, on a table near a window or in the shade of other plants, otherwise the plant can get a sunburn. The intensity of illumination can be judged by the state of the leaves of the orchid, if their color becomes lighter, with yellowness or whiteness, then in this case too intense illumination takes place. In the absence of sunlight, on the contrary, the leaves of the orchid have a darker green color.
This kind of orchid refers to a moderately warm temperature regime, and it is recommended to keep the orchids under the following conditions throughout the year:
Day temperature at 20-30° C and Night temperature at 14-23° C . To successfully grow Tolumnia at home, it is necessary that the night temperature of the content is always 5 ° C lower than the daytime temperature. They will endure occasional deviations, but extremes lower than 14° C and higher than 32° C for any length of time should be avoided.
This is the most crucial aspect to success with tolumnias. There is no hard and fast rule for how often to water. Watering directly depends on the temperature of the content, the higher it is, the more often and abundant it is necessary to water. Plants growing on blocks should be watered daily in the morning, so that by evening the roots of the orchids could dry out relatively well. When watering orchids in pots, it is necessary to remember that excess water during watering should flow freely out of the pot, as the stagnation of water both inside the pot and in its pallet can very quickly lead to rotting of the roots and the lower part of the plant. The substrate between waterings should dry well.
On hot summer days, daily spraying of the outer part of the plant is recommended, which will additionally increase the humidity of the air around the orchid and help it better survive the heat. Water that collects in the overlapping leaf bases can reach "cooking" temperatures and severely damage plant tissue, especially the tender young growths.
For normal growth and development the relative humidity level of 45-70% will be enough. For plants planted in blocks, a higher air humidity is desired than for a pot culture. Too dry air negatively affects the development of the plant, its growth is inhibited, and the roots of the orchids begin to dry out. The higher temperature rises, the higher must be the humidity of the air, and the higher the humidity of the air, the more often and longer it is necessary to ventilate the room where the orchids are kept, otherwise there is a high probability of decay and appearance on the leaves of various fungal diseases.
Using a Humidity Tray is one of the best ways to achieve any humidity level. These trays are nothing more than a water-holding tray filled with gravel. The gravel-filled trays are filled with water to a level just below the surface. To prevent plants sitting on constantly wet gravel the plants are placed on small saucers or pieces of plastic or metal grid placed on top of the trays. A plump lead pseudobulb indicates a well-hydrated plant.
Flowers are produced primarily in the spring on 12- to 18-inch inflorescences that are often branched on older plants. Some types have much shorter, bouquet-like displays.
"Do not cut the inflorescence after initial flowering. It will often branch and continue with another flush of blooms"
To stimulate flowering, Tolumnia needs a clearly defined period of rest. It is necessary for the period from November to February, and is that the orchids contain much drier than usual, and do not fertilize. Watering the orchid growing in the substrate, it is necessary to replace it with light spraying and perform this procedure no more often than once in 3-4 weeks. For orchids on blocks, the irrigation frequency is reduced to one time in 10-15 days. After the appearance of peduncles, the rest period ends and the watering of the orchid resumes in the usual volume.
In the natural habitat, plants are bathed with nutrients derived from decaying plant and animal matter with every rain. So, for cultivated plants, frequent and dilute feeding is the preferred approach. A balanced fertilizer applied every second or third week should be adequate. Flushing with plain water between feedings is important because residual salts can damage the roots.
Balanced Fertilizer for Growth: 20-20-20 (NPK) – 2 grams per litre of water – Spray once in every alternative weeks (14 Days) - On Resting Periods (Once in a Month)
High-Phosphorus Fertilizer for Blooming: 0-52-34 (MPK) – 1 gram per litre of water – Spray on every alternative weeks (14 Days) - Except on Resting Period.
Potting , Media and Propagation
Frequency of watering and selection of substrate are closely integrated. The objective is to achieve the proper combination allowing for good irrigation with adequate aeration and rapid drying of the root area. Mounting is the method of choice; at least for a start. Twigs, cork bark, small wood or tree-fern plaques all work well. Place a pad of moss or coconut fiber around the roots. A daily light misting will help establish growth. If plants on mounts show a tendency to shrivel despite regular waterings, this may indicate conditions drier than optimum. Pare off some of the mount without disturbing the plant and simply set it in a clay pot (with no medium). This procedure may afford just the right amount of extra moisture around the root area.
If conditions still seem too dry, sift potting mix into the container around the base of the plant. The medium used should be porous and drain readily. As a substrate, the mixture of the bark of coniferous trees and moss sphagnum in a proportion of 5: 1 is best. Pots for planting should be used small and narrow, exactly the size of the root system of the plant. When growing orchids on blocks, it is recommended to cover the roots of the plant with moss, this will be a good protection against very rapid drying.
From frequent irrigation and fertilization, the substrate quickly decomposes and loses its main useful property for orchids - air permeability, therefore it is recommended to replant Tolumnia at least every 2-3 years. The best time for this is considered the period immediately after flowering.
Unless plants are cultivated in a basket, a 3- to 4-inch pot full is the maximum size to which a plant should be allowed to grow. When this size is reached (every two years on average), divide and repot the plant. Otherwise, as the central part of the plant begins to decline it may affect the healthy portion through bacterial or fungal rot. Repotting should be done when new growth begins in the spring to assure quick establishment in the new quarters.
“ As Adaptable, there is no Single Best Potting Medium”
Pests and Other Tolumnia Related Problems
Fungal and Bacterial Diseases of Tolumnia are common because of the levels of humidity and substrate they need to survive. Fungal agents cause problems like root rot, leaf spots, leaf blights and spots on flowers.