As autumn settles on the greenhouse it is time to look ahead to spring next year and the shows we will be attending. Amongst the team we will need to decide who is going to be responsible for creating our displays, plants we can add to our sales table and of course looking at our plants to plan what may be in flower for each. We have included shows on our Events calendar but here is a summary up to April 2019.

Wednesday December 12th – Orchid Christmas – Writhlington School from 6pm-9pm – orchids, mince pies and mulled wine in the tropical splendour of the school greenhouses.

Saturday 2nd March 2019 10.30 am to 4.00 pm – Cheltenham & District Orchid Society Annual Show – Churchdown Community Centre Parton Road, Churchdown Gloucester GL3 2JH – We will be displaying and selling.

Saturday 30 March 2019 and Sunday 31 March 2019 – 10.30 a.m. to 4.30 p.m. each day – Bournmouth Orchid Society 60th Anniversary Show, Highcliffe Castle, Rothesay Drive, Highcliffe, Christchurch, Dorset  BH23 4LE – We will be displaying with a have a go lab and selling plants.

Monday 8th April (Late event), Tuesday 9th April (10am-5pm) and Wed 10th April (10am-5pm) – RHS London Orchid Show – The Lindley Hall, Elverton St, London SW1P 2PB – Our 18th London RHS Show with our biggest display yet and an amazing range of orchids for sale.

Some of our orchids are compact and convenient to grow others are not. These very attractive flowers belong to one of our more challenging Brazilian species.

This relative of Oncidium grows 3cm pseudobulbs separated by 15cm of vertical rhizome and so rapidly climb up from any basket or support they are given. I am sure this is a useful habit when you grow as an epiphyte in the coastal cloud forests of Brazil where plants presumably clamber their way up through the canopy to get access to more light and attract pollinators. However, in a greenhouse we are always playing catch up and keep up with the plant.

We have recently done lots of dividing to bring our large plant back down to a manageable size and so if anyone wants to try something a little different we will have plants for sale.

This remarkable orchid is one we have seen growing in hot dry rainforests in lowland Guatemala and in cool mountain forest in Brazil. The range of the species has actually been recorded from Mexico to Argentina and from 300-3900m altitude. Few orchids exist across such a range of habitats.

We first observed the species in Brazil where it was growing as a lithophyte on a South facing (Shady) rock face above primary forest at 1200m altitude. Plants were surrounded by moss and were growing cool damp and shaded. In Guatemala plants were growing as epiphytes low in trees (so again in shade) but the habitat was hot and seasonally dry. In Costa Rica we found the species thriving in mature regrowth forests at 1400m

When it comes to growing plants in cultivation it would seem difficult to identify the correct conditions but I expect plants would thrive in both our Cool Americas and Warm Americas sections. We know that our plant is seed from the Brazillian population as we purchased it in flask from Equatorial Plants and so we have opted for the cool damp shady habitat we observed there.

Plants flower once a year from the ends of this years growths and the long lasting flowers give a pretty display despite being small. The species is humming bird pollinated which explains the terminal pendulous nature of the plants.

This is the second article about culture at the Orchid Project. The vital topic of temperatures.

We run our greenhouse at a range of temperatures to allow us the grow a diverse range of species and each section is based on one or two of the habitats we have experienced on our expeditions to South and Central America, the Himalayas, South East Asia and Africa.

Temperatures are related to both the altitude and latitude of the habitats we are recreating so in simple terms it gets cooler as you climb a mountain or travel away from the equator. At 3000m altitude at the top of Mount Bigugu in Rwanda (on the equator) it is cool but not freezing in the winter with Erica scrub and orchids such as Disa starsii and Polystchya spatella (below)

At 3000m in Sikkim in March 3000m is a cool place with the snow not much higher up the mountains and the only orchids are hidden away under the snow or like Pleione hookeriana, leafless and buried in deep moss on tree trunks.

 Lachung at 3000m Sikkim and snow at 3700m at Yumthang 

Of course we have also been to some very hot places with lowland Guatemala in July probably the hottest with the temperature at night falling to around 28C and the day time temperature in the high 30s.

 Hot work collecting orchid data in Guatemala near Yaxha.

The next key to temperatures in greenhouses is to consider both the minimum temperature and the temperature at which the vents open. This does not give a maximum temperature but does significantly affect the day temperature during much of the year.

We have five distinct section and I will give our minimum and vent open temperatures for these as well as the habitats we feel these sections replicate from our expeditions.

Temperate – Here we grow Cymbidiums, Coelogynes, Pleiones, Native species and Australian Species  – The vents are open most days even in the winter giving this section a very fresh feel. We shade above 400W/m2 and water heavily in the summer but a less in the winter. Several species here grow cooler than many books recommend but we find that the plants flourish in these cool airy conditions. In the summer we leave the door open in hot June/july weather but do not worry to much about high temperatures (regularly above 30C) as we keep plants very wet.

Cool Americas – A wide range of species from the mountains of Central and South Americas (as well as a few from Africa) Shady damp and cool is the target. Plants are packed in and help to maintain their own humidity and cool conditions. We find niches for plants that enjoy deeper shade or more light by hanging high or low in the greenhouse.

Warm Americas – This is not a very warm section as most Cattleya species do come from mountains but below 1000m. This section is brightest reflecting our experience of forests in Guatemala (shade above 500w/m2

Warm Asia – Our warmest section at 18C is not warm enough for some heat loving lowland species but matches the lowland forests we have seen in the Himalayas and south East Asia. The majority of tropical diversity is not found in very hot lowland forests and this is probably due to the impact of the ice ages when the global climate dries and tropical forests retreat to mountain rufugia.

Cool Asia – Is where we grow the majority of our Himalayan species (from 1000-2500m altitude), Coelogynes, dendrobiums and cool growing species from other areas such as the mountains of Madagascar that experience similar cool tropical conditions.

What about high summer temperatures?

The question we most often get is about how we cope with high temperatures in the summer (especially after this summer). A lot of books and references suggest that for cool growing orchids you should keep temperatures below 26C and people panic when their temperatures go over 30C in hot weather.

As shown in the table we have our vents automatically open to give a ‘maximum’ temperature in cool weather but of course in June when it is 28C outside the greenhouse temperature often goes over 30C and this year we recorded a record of 35C in Cool Americas. Our philosophy is that if plants are well watered wet at their roots they can cool themselves through transpiration so in hot weather we shade (additional internal shading gives areas where leaf temperatures are kept cool) and water well – that means every day and twice a day in extreme weather especially for mounted plants.

Some species do suffer in very hot weather particularly Dracula species and some Masdevallias where we get leaf damage (black spots and dropped leaves) and for these species we try to keep plants happy by hanging or moving them right down to floor level. If a plant really can’t cope with UK summer temperatures we don’t grow it. We certainly find that the cool growing Himalayan species such as Cymbidiums and Coelogynes don’t mind the hot weather as long as they are really wet.

Some of our warmer growing species really appreciate hot weather and put on a real growth spurt – again water is important to help this.

What about cold spells in the winter?

As I have already said there are some species that would like to grow warmer than our Warm Asia minimum temperature. If we have several days of sub-zero temperatures and snow the greenhouse will tend to sit at the minimum temperature and when this happens we try to avoid to much water on the leaves of these warm growing plants. We do need to water in cold spells though as the heating working hard tends to dry plants out. remember that the top of the greenhouse is significantly warmer than bench level.

As we have thermal screening that automatically deploys, at night and when the outside temperature is below zero, we do override the system to open the screening in the day to let the plants enjoy some light in a prolonged cold snap.

If the Temperate section has been at 6C for several days, and has not warmed with sunlight on the greenhouse, we do open the doors to Cool Americas to allow a day time rise in our coldest section

Last month we featured our large clone of Pleurothallis tuerkheimii and today we feature the smaller growing and pendulous clone.

The natural habitat of the species is damp forests and cloud forests from Mexico to Panama between 700m and 2400m altitude. As I explained last month, this broad natural range supports our observation that this is an adaptable and accommodating plant to grow.

In comparing the two forms the smaller pendulous form seems much less tolerant of high temperatures and bright light (suggesting it is found at higher altitudes than the larger form) and as a result we grow the  plant in deep shade low in the Cool Americas section against a north facing wall.

The larger clone is shown below and shows the upright growth and spike habit compared to the dramatically pendulous habit of todays form.

One of the delights in observing and growing orchids is to spot the variations within a species and we love to hear any observations on this species or others we feature.