The species of the genus Cymbidium are perhaps the most appreciated flowers from the point of view of the world horticultural trade, mainly due to the high productivity of flower stems, the ease of growth, the dimensions, the persistence, the floral color and the presence of the perfume. The species considered classic come from the hilly regions of Nepal and Sikkim, rich in sun, where a rather cold climate prevails, and the growers of this group must reproduce these conditions in order to be able to enjoy the success of flowering.

Known in culture and among collectors by the generic acronym HTC (Heat Tolerant Cymbidium) , this functional and geographical group includes taxa of small size (30-50 cm, compared to 80+ cm in the classic species), with strongly scented, durable flowers (at least 4 weeks), on numerous stems, erect or hanging, multi-flowered (5-60 flowers), which grow and bloom in tropical climates without drastic temperature differences between day and night , unlike the species and hybrids of the genus considered classic, where it is necessary for the night temperatures in the winter season to drop to values ​​of 8-4 ℃ to trigger flowering. Hybrids of the HTC group are generally obtained by crossing tropical, heat-loving species (ensifolium, aloifolium, canaliculatum, finlaysonianum, sinense, atropurpureum, madidum, dayanum). From the point of view of culture, HTC is very close to the procedures applied to the growth of Dendrobium hybrids.

One of the essential elements for the flowering of HTC hybrids is represented by the light radiation, which must cover a minimum duration of 8 hours per day, with a maximum of 40% shading for the growing period, but following that on hot summer days it should be increased to 50% to prevent sunburn. A good indication that the plants receive enough light is represented by the raw green color of the leaves, in the case of plants grown in low light conditions, the leaves are colored dark green. In the case of species with hard leaves (aloifolium, canaliculatum, finlaysonianum), similar in terms of consistency to those present in species of the genus Cattleya, exposure to stronger light intensities is allowed and even recommended, they can even tolerate direct light for several hours per day.

Greater attention will be paid to irrigation, HTC being more rigorous in this regard. Stagnation of water in the substrate for long periods will be avoided, but care will be equally taken that the root block never dries completely. Equally, and also as a similarity to species of the genus Cattleya, hybrids with hard leaves can tolerate longer periods of dryness and less frequent irrigation, appreciating even the complete drying of the substrate.

The optimal growth temperature for HTC species and hybrids will fall within the range of 15-35 ℃, which will ensure repeated flowering, usually at least twice a year. However, a consequence of the tropical ascendant is represented by the low tolerance to cold, it is not recommended to expose the representatives of the group to temperatures below 10 ℃ for long periods of time.

Atmospheric humidity is not an important factor for Cymbidium HTC varieties, they are particularly tolerant in this sense.

The ideal culture medium for this group is represented by pine bark, sometimes fined with perlite, and pots of high height or at least larger than the diameter will be used as culture containers, as the roots of these taxa tend to sink deep in the substrate. Most of the species that form the basis of this group are epiphytes, except for Cymbidium ensifolium, which prefers terrestrial habitats, this aspect being noted in its hybrids as well. Fertilization will be done every two weeks during the growth period using a fertilizer rich in nitrogen or a balanced one, and once a month during the flowering period, with a fertilizer rich in phosphorus and potassium.

Some prestigious authors and breeders, such as Kobsukh Katraena from Pakkret Orchids, Thailand, propose the following classification of several species according to thermal tolerance, with a guiding role in its evaluation in the hybrids that will have them in the component:

Taxon Thermal tolerance

Cymbidium ensifolium subsp. haematodes 10.0

Cymbidium canaliculatum 10.0

Cymbidium aloifolium 10.0

Cymbidium finlaysonianum 9.5

Cymbidium ensifolium subsp. ensifolium 8.5

Cymbidium dayanum 8.5

Cymbidium bicolor 8.5

Cymbidium atropurpureum 8.5

Cymbidium madidum 8.0

Cymbidium munronianum 8.0

Cymbidium chloranthum 7.0

Cymbidium sinense 5.5

Some of the Cymbidium HTC hybrids: - Cymbidium Golden Elf (variegated leaves) - Cymbidium sinense × Golden Elf - Cymbidium Kusuda Fantasy

The complete offer of Cymbidium from Secret Garden is available here (link).

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