Growing cool orchids from South and Central Americas

At Isle of Portland Orchids we grow around 300 species native to the cool mountain forests of South and Central America. These wonderful orchid species include our dramatic Masdevallias, miniature Stelis and iconic cattleya species.

Stelis gutifera flowering in Brazil

Orchids in the wild

Over the past twenty five years we have visited orchid habitats in South and Central America several times exploring the hot lowland forests of Guatemala and Belize and the remarkable cool tropical forests of Brazil and Costa Rica. In Brazil and Costa Rica we have seen many of the species we cultivate flourishing in their natural habitat. Our culture at IOPO is based on observations of how these orchids grow in the wild. If we make our orchids feel properly at home we can expect them to flourish.

In Brazil we have twice visited the Mata Atlantica cloud forests around Macae de Cima as the hosts of the Rio Atlantic Forest Trust. This incredibly rich forest has taught us a lot about orchid culture and in particular drew attention to the specific microhabitats enjoyed by so many orchid species. For example the species found on a windy ridge of elfin forest would be replaced by a different group of species in shady wet forest 100m away. This is a reminder to look for the microhabitats within your greenhouse.

This image shows the Organ Mountains in late afternoon in the dry season. The mountains here rise to 1500m altitude and as you can see are clothed in evergreen forest. As the sun sets temperatures fall and mists develop across the forests. The result is that every morning (even in the dry season) the forests are dripping with water (photo below)

So although the coastal cloud forests in Brazil have a distinctly seasonal climate (warmer wetter summers and cooler dryer winters) orchids here are never without moisture for long.

We recorded temperatures up to 24C and down to 9C in our visits. (More on temperatures later)

So lets look at some of the orchids we found in Brazil.

Cattleya coccinea in elfin forest

The first orchid we must talk about is Cattleya coccinea. This is a miniature Cattleya with leaves 6cm long and stun ning red flowers 10cm across attracting hummingbird pollinators. The species was most abundant on mountain ridges in elfin forest (forests where the low nutrient supports a dwarf mossy forest) the plants were mostly surrounded by moss, exposed to the sun, wind and mists.

In cultivation we replicate these conditions growing plants near the top of the greenhouse for good light but spraying every day to keep plants damp

.Cattleya coccinea in our greenhouse.

Many other orchids were in more shaded spots such as this Pleurothallis grobyi on a mossy branch.

One quickly realises that a mountain rainforest is packed with microhabitats exploited by different species.

Miltonia cunneata grows high on the semi shaded trucks of large trees.

Oncidium marshallianum enjoys open spots in the forests exposed to more sunlight

While the small growing Stelis littoralis grows in damp shady spot

Exploring Brazil encouraged us to find microhabitats in our own growing spaces.

Costa Rica is a remarkable country essentially consisting of a north West to south east row of volcanoes with oceans to the East and the West. The resulting tropical climate has a dryer period from December to April and a rainy season from May to November but altitude has a big impact on rainfall as well as temperatures and in the cool forests above 1200m there are mists and rainfall all year. The result of all this moisture is a lush forest with abundant epiphyte

The photo above shows the epiphyte filled forest on the slopes of Poaz volcano at 1400m

As can be seen from the photograph of forest on the Poaz Volcano, massed bromeliads, ferns, mosses and orchids cover every part of the taller trees. We found a number of charismatic orchids growing in this epiphytic mass although most were only identifiable through good binoculars or on fallen trees and branches.

Pleurothallis ruscifolia growing mostly in shade in Costa Ric

Pleurothallis ruscifolia growing mostly in shade in Costa Rica.

Masdevallia calura at 1400m

Platystele compacta with plants just 2cm across

Orchids in cultivation

Lets have a look at how we replicate these conditions in cultivatio

Orchids in cultivation

Lets have a look at how we replicate these conditions in cultivation.

Our Cloud Forest Greenhouse has a minimum temperature of 11C with the vents opening at 17C in an attempt to replicate the conditions of cool temperatures we have experienced tropical forests.

We shade the greenhouse with external shade net from March until October with an additional layer on the roof during June and July.

We then make use of the variation between conditions at the top of the greenhouse - warmer, brighter and dryer - and the floor of the greenhouse - cooler, darker and damper - to match our orchids to their prefered microhabitat

Low in the greenhouse we grow many of our smaller masdevalias, pleiurothallis and stelis. We grow these species mounted and they enjoy the cool shade. We have similar conditions on our lower shelves, ideal for miniatures in pots (Platystele misasiana below)

In the middle of the greenhouse we grow our larger Masdevallias and other pleurothallids in baskets

Leaving room towards the roof for our light lovers and warmer species such as Barkeria skinneri

One of the most troubling challenges to many growers is the maximum temperatures often advised for cool growing species from the Americas. We can confirm to climate records for these habitats that temperatures in the day time stay very comfortable in the low 20s Celcius and temperatures below 24C in the day time would be great to achieve in our greenhouse.

However, let’s be realistic the temperature in the UK is frequently well above 24C and in out greenhouse it is always warmer than outside. In the hottest days of May, June, and July the temperatures in our Cloud Forest Greenhouse section frequently exceed 30C.

In the past we have panicked at such high temperatures and have responded with under bench sprayers and several visits a day on weekends to open doors and try to cool things down. These days we are much more relaxed. Our observations have lead us to the conclusion that the issue for plant health in warm weather is not air temperature but leaf temperature.

Leaf temperature is cooled by shading and with watering as leaves are naturally cooled by transpiration. A cool growing masdevallia will suffer in the heat if it is dry and unshaded but if wet and shaded we find that most species show no ill effects at temperatures in the 30’

Masdevallia triangularis

Watering

We water heavily in our Cloud Forest Greenhouse. In most of the year this means watering daily or every other day and on hot summer days we may water twice daily. We water with a hose supplied by an inline pump from our rainwater feeding tank in the greenhouse and include feed at around 300-500μS.

To cope with the heavy watering we use large bark and no moss although natural moss tends to develop on top of most pots and baskets. We grow plants in small pots, mounted and in baskets

Pleurothallis truncata grown on a middle shelf.

Probably our most challenging plants are the ones that want it wet and bright (such as Cattleya coccinea and Casttleya wittigiana) and we make a point of hanging these in very easy to reach spots so that they don’t miss out on their watering just because they are up in the light. (notice the moss that has grown on the Cattleya wittigiana mount)

We don’t damp down in our greenhouse for four reasons. Firstly damping down to maximise humidity will reduce the efficiency of transpiration which requires a higher humidity inside the leaf than outside. Reduced transpiration will reduce the leaf’s natural cooling and so increase heat stress. We have also recorded humidity in the forests we have visited and find that the humidity naturally falls each day to around 50% as the temperature increases (simple physics) The second reason is safety as too much damping down creates a dangerously slippery floor, and thirdly damping down is very wasteful in water. We are 100% self sufficient in rain water collected from the greenhouse roof and do not use mains water at all in our greenhouse.

Growing orchids indoors

I have talked at length about how we grow plants in our Cloud Forest Greenhouse, how can we grow similar plants indoors?

The first principle is to again consider microhabitats. A south facing window is very hot and bright but on the opposite wall facing the window it is shady and much cooler. A north facing window is a wonderfully even cool habitat. I have said that we are not obsessed by humidity, but ideal ways to raise humidity for cloud forest orchids is to group plants together, or enclose plants in a cabinet, tank or terrarium. We do not grow in terrariums but are delighted to hear the success stories of customers who grow orchids from cool mountains of the Americas really well. - Please send us some photos to share in this article.

We grow our indoor orchids in IKEA display cabinets and on windowsils.

These Ikea cabinets are opposite a north facing window and so we supplement light with LED grow lights which were not difficult to add to the IKEA units. Our plants are mostly in pots and we spray every other day with a pump sprayer

Our windowsil plants live in our downstairs bathroom. This is a cool room and the window faces west but is shaded by a tree so the plants afre evenly cool and shaded. As you can see we have cut a 6cm carry tray to fit the tray they are sitting in. This makes them easy to water with our sprayer and stops them falling over.

Pleurothallis amparoana

The wonderful thing about growing cool orchids from the Americas is the fantastic diversity of plants that can be grown together. Every time I push my way past Miltonia cunneata to catch sight of an interesting Stelis species I find myself transported back to the magnificent cool mountain forests we have explored on our memorable expeditions.