Monday, November 22, 2010

Calanthe rubens and Cal. Grouville two terrestrial orchids that are relatively easy to culture

Calanthe Grouville a hybrid

Calanthe inflorescences cascading from my terrace

Here you can see the way the flowers of Calanthe Grouville change color in my garden

A large plant of Calanthe Grouville with inflorescence

Calanthe Grouville plant with inflorescences that have been blooming for months

Plants ready for repotting, you can see the new buds at the base of the pseudobulb, for more details see text

This pesudobulb has two developing buds
Calanthe rubens

A mass of Cal. rubens inflorescences

Here you can see the shape of the Cal. rubens pseudobulbs

From what I have read about the start of the orchid hobby in England in the nineteen century, it seems the genus Calanthe was widely grown and much admired. In fact the first orchid hybrid to bloom, although not the first one ever made, was Calanthe Dominyi (Cal. masuca x Cal. furcata). Nowadays Calanthe has become rare in the orchid market although it still possible to find hybrids and species if one searches for them hard enough. But in Puerto Rico Calanthe has never been a popular genus and most orchidists are unfamiliar with even the most common species. I will detail my own experiences with this genus and why I think it is not favored among local growers.

The genus Calanthe has two group of species, the evergreen and the deciduous ones. General guidelines for the culture of both groups are similar in some respects but their biology also makes up for some major and striking differences. I have never grown evergreen Calanthe and I have never seen them shown in local orchid shows so I cannot comment about them. Those evergreen species I know from the literature hail from temperate climates and probably would die if kept at the tropical temperatures of the island of Puerto Rico.

My experience growing Calanthe has been with a deciduous tropical species and a hybrid of the same type. The species is Cal. rubens, the hybrid is Cal. Grouville. Calanthe rubens produces small pink flowers over a period of a few weeks in an erect inflorescence. Calanthe Grouville produces flowers that are somewhat larger than those of the preceding species and that are white and red. I my locality, and I don’t know if this is true elsewhere, the flowers of Calanthe Grouville start turning pink as they age. The flowers of Cal. Grouville open over a period of months on a single inflorescence that arises from the base of the pseudobulb.

Let’s start with the species, Cal. rubens. I suspect that the seasonal growing and resting cycle of this species is probably the source of confusion and frustration to orchid growers whose whole experience growing orchids is circumscribed to growing ephyphitic orchids such as Cattleya, Dendrobium and Phalaenopsis. The reason for the confusion is that for part of the yearly cycle of this species the plant discards both its leaves and the root system. The pleated leaves that looked so elegant earlier in the year start to deteriorate as soon as the inflorescence becomes close to blooming and become yellow and fall just as the first flower is opening. This seems to be a source of distress for those orchids growers unfamiliar with this plant and some assume the plant is sick and is going to die. The fact that the leaves of Calanthe tend to look awful and the end of the growing cycle, even before they are shed is also something that doesn’t endear it to growers that prefer clean and immaculate leaves on their plants.

Cal. rubens blooms at the start of the year in my garden, plants bloom between January and February. In this stage of their yearly cycle they are normally composed of an older pseudobulb and the current year’s growth with a single inflorescence arising from the base of the newer pseudobulb. The plant has neither leaves nor roots and the pseudobulb supplies all the needs of the inflorescence. At this time I water my plants but the plants seem to survive equally well with no water at all. I water them to avoid having the pseudobulbs become too withered. When blooming is getting close to finishing a rapidly growing bud will appear at the base of the newest pseudobulb. This is the signal I use to repot the plants. I take the plants out of the pots, I trim the old dead roots but leave the base of the roots still attached to the pseudobulb to help anchor the plant in the new potting media.

The plant should be repotted just as the new growth starts developing its roots. I tend to repot at an earlier time when the new growth is pretty small but I do this mainly because I have on occasion damaged the new growths when I have waited too much to repot them and they are quite large. I have used several types of media such as potting soil, peat, compost, sand and I have not noted much difference in the growth response of my plants. However there are two things that seem to have a great influence on the growth rate of the plants. First is the inclusion of manure in the potting media. If the media is around 1/3 manure the plants do much better. You might want to ask, Isn’t that a lot of manure on the media? The answer is, yes, but that what works for me. Second if the media is loose and easily penetrated by the roots the plants grow more vigorously. Calanthe in compacted hard to penetrate media produce smaller root systems and stay smaller than those grown in fluffier media. When the plants are in full growth mode I give them daily watering and in those cases when I have a large pot full of pseudobulbs I will even go so far as to put a water dish under the pot to ensure that there is enough water to sustain their rapid rate of growth.

I divide my plants every time I repot them, Calanthe is one of the few orchid genera where a single pseudobulb can produce a new full sized new pseudobulb without the back up of older bulbs. Depending on my mood I might plant them one bulb to a pot, two or even a dozen in a single pot. If they receive the proper level of light and watering they will do well in any number of combinations. I don’t give them the water soluble fertilizer when I water them since the manure in the potting mix takes care of their fertilizer needs for the whole growing season.

My plants produce their growths during the summer when local temperatures can climb into the nineties and it rains almost daily. They bloom in the colder and drier part of the year when a whole month can go without significant rain.

They get full sun most of the morning and shade from 11:00 am on. Exposure to too strong sunlight burns the leaves and leaves them covered with bleached yellowish areas and dead spots. But plants grown in the shade are weaker and bloom poorly. It takes a bit of experimenting to determine which exposure best suits the plants in your location. I try to achieve the elusive slightly yellowish and yet not covered with dead spots areas that brings the best blooming results in my area.

I treat my Calanthe Grouville the same way as Cal. rubens but since the pseudobulbs are much large I make allowances for a larger adult size. Cal. Grouville can form large avocado sized pseudobulbs and produces beautiful pleated leaves. It grows enthusiastically under tropical conditions and sometimes produces two growths at the same time from a single pseudobulb. Its inflorescences can get much larger than those of rubens reaching a meter or more. It produces its relatively short lived flowers in sequence as the inflorescence elongates. The inflorescence can have one to three flowers at a time. My personal problem with Cal. Grouville stemmed from its proclivity to proliferate at a furious pace if given good care. Since every year the number of pseudobulbs duplicate I found myself with dozens of plants. Because these plants are not small, finding a place to put them became a chore. I recall one year that I had so many that I gave every member of my orchid society a pseudobulb to plant and grow.

Cal. Grouville can stay in bloom for months but the inflorescence is at its most beautiful when it is opening its first few flowers. Afterwards it becomes leggy, in some cases the inflorescence can arch downward and eventually reach the ground which doesn’t stop it from continuing to bloom. This Calanthe is particularly striking in massed displays in which many plants are shown together.

My Calanthe seem impervious to most diseases but sometimes the pseudobulbs can rot if kept too wet when they are supposed to be in the dry season. One peculiarity of these plants is that sometimes the pseudobulbs produce small plantlets from their tops. Calanthe rubens pseudobulbs have a constriction in their top half, this makes the top half vulnerable to snapping off from the plant if the pseudobulb is handled too roughly. But if this shouldn’t cause alarm as the snapped top can be planted on its side and it will eventually produce a plantlet from its top that can be reared without difficulty.

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