Luke Callaghan lives in Newtonhill, on the North-East coast of Scotland, and he has a passion for growing the absolutely stunning Odontoglossum orchids, a genus of about a hundred cool climate orchids, native to the Andes and other mountainous regions. 

Luke became fascinated with orchids from a really early age when his mother took him to the 14th World Orchid Conference in Glasgow in 1993. He started growing orchids seedlings from the age of nine, on window sills in his parent’s house, moving on at age fourteen to building his first basic vivarium from perspex.

Glasgow was selected as only the second-ever European venue for the 14th World Orchid Conference on the strength of the reputation of the city’s Botanic Gardens, which has its own orchid collection, and the environmentally-controlled conditions which the SECC could offer to house many rare specimens from Thailand, China and Brazil. The conference was an outstanding success, with over 20,000 visitors and 1,300 delegates from around the world.

We asked Luke to tell us more about these fascinating plants, his enthusiasm for growing them and his hopes to hold a National Collection.

Paphiopedilum Rothschildianum 

“At the 14th World Orchid Conference, I saw a plant which was completely awe inspiring to a nine year old. With the flower spike at over 1 metre tall and each flower being over a foot wide, the flowers of this orchid looked like condors soaring through the air: I had never seen anything like it in my life!

“Called Paphiopedilum rothschildianum ‘Mont Millais’, bred by the Eric Young Orchid Foundation, this orchid was awarded the Grand Champion plant at the Conference and I wanted one! With a price tag though at over £1000 for this king of orchids, it was a little out of the reach of a young aficionado.

“Another Paphiopedilum orchid which cemented my boyhood orchid obsession was Paphiopedilum sanderianum. It has arguably one of the largest flowers in the world and the petals can be in excess of 1metre long. This orchid was lost to science for about a hundred years and modern plant growers only had Victorian paintings for reference. The petals were so long that people believed the paintings to be exaggerated until the orchid was rediscovered in Borneo in the 70s. The P. sanderianum is so rare in cultivation that when mine flowered earlier this year it may well have been the only one in flower in Europe.”

Odontoglossum Orchids
“I chose to specialise in Odontoglossum orchids when I was around twenty seven due to their obvious beauty. No other orchid family has the mix of colours that these orchids offer and once their cultural requirements are understood, they flower every year. 

“The other reason I grow Odontoglossum orchids and probably the most important one, is their rarity in cultivation. There is a very real chance these orchids could disappear as so few people grow them. It terrifies me that some of the most stunning plants to ever evolve could be lost without people ever knowing they existed.”

Growing Conditions
“Odontoglossum orchids are difficult for commercial nurseries to grow and as such there are few orchid nurseries who grow them. The species require cold conditions and high humidity: maximum temperatures in summer of around 25C and winter night temperatures which get down to down to 8C, are perfect. 

“Odontoglossum orchids cannot successfully be cultivated at home without grow tents, lights, humidity meters and ideally, a cold greenhouse. My current greenhouse is 10 foot by 6 foot and is insulated with rubber tiles on the floor with gravel underneath to minimise heat loss through the floor. 

“There are two layers of bubble wrap over all the glass, a 3kw greenhouse fan heater and two automatic roof vents, plus an air circulating fan as orchids enjoy strong air movement. 

“I set the window vents to open at 22C as this is hot for this type of orchid and I keep the greenhouse at a minimum temperature of 10C or so in winter. Odontoglossum orchids need a temperature drop or there will be no flowers. Through the summer I leave the door open and pour water over the floor to reduce the temperature. Believe it or not, night temperatures in Scotland can be too hot for these orchids –  they do not like anything above 12C at night.

“The plants also require heavy shade so I paint my greenhouse with white greenhouse shade paint and use a double layer of green shading through the late spring to early autumn. In winter, I remove the green shading and leave the white paint.”

Time
“I spend about half an hour each weekday with my orchids and about two to three hours at the weekend, usually consisting of checking the plants for disease and bugs and looking for new growths and flower spikes. I sometimes go out at night with a torch to catch slugs who love to eat the buds. Being out in the greenhouse is a great way to unwind and relax after work or at the end of a long week. Seeing the plants in flower is great and is the point of growing the plants but I get a lot of satisfaction from growing a plant well. It is great for my mental health and through Covid, it has really helped me deal with the added strain of the pandemic.”

Hybrids
“I started producing my own hybrids only recently. Orchids are difficult to grow from seed, in nature they form a symbiotic relationship with a fungus and this must be replicated in a laboratory. I have to send the seed to a specialist lab where the seed is sown onto agar jelly under sterile conditions. The process from seed sowing to seedlings being removed from the flask, takes about eighteen months and then it’s another five years until the new hybrid flowers. My first hybrid is about two and a half years old now so a while yet before it flowers. 

“The other benefit of making your own hybrids is you can name them and I hope to follow in the footsteps of some of the world’s great hybridisers.” 

Plans for the Future
“Orchid growing can become a true addiction and I’m already thinking of my second orchid greenhouse having only built my current one two years ago.

“I now own a collection of around a hundred Odontoglossum orchids and with my own unique hybrids, I hope to have a National Collection in the future allowing people to view my orchids and become inspired to grow them too.”

Top Tips for Growing Orchids
Phalaenopsis orchids are by far the most common orchid to buy in shops. Many people buy them in full flower and when it does not re-flower, throw them away, perpetuating the myth that orchids are hard to grow. Some orchids are hard to grow but not all and we asked Luke for his top tips for keeping orchids alive and blooming in our own homes!

Growing Medium
“I grow virtually all my orchids in clear pots because orchids roots are green when wet and photosynthesis just like the leaves. The growing medium is a mix of 20% orchid bark, 20% perlite and 60% sphagnum moss. This allows lots of air to circulate around the roots and crucially ensures the plants are not water logged.” 

Watering
“Don’t overwater orchids, this is the quickest way to kill them Treat them more like a succulent than a houseplant, almost all orchids have some kind of water storage facility. The quickest way to kill an orchid is to leave it sitting in water.

“Orchids grow best with rain water which does not contain chlorine so beneficial bacterial colonies thrive, giving a better uptake of nutrients to the plants. If you have no rain water, leave tap water for 24 hours in a jug which will remove the majority of the chlorine and will allow it to acclimatise to the right temperature. 

“The drawback of rainwater is its purity so I add nutrients like seaweed extract with added iron, Epsom salts and low urea liquid fertiliser. I buy specialist orchid fertiliser from a nursery and use this at half concentrations at every watering through spring and summer; in autumn and winter I only do this once a month. It is also important to wash through once a month with pure rainwater to remove salt build up.

“Create humidity around the plant by using a tray with pebbles and some water.”

Light
“Light is very important: generally orchids need bright light but not direct light as can burn the leaves so an east facing windowsill works well. Diffused light is ideal so use a net curtain between the plant and the window.

“Put the orchids outside in the summer in a shady spot from the start of July until the end of September to improve the likelihood of the plant flowering. This will produce more robust growth and better flower colour.”

Temperature
“The temperature drop from day to night is crucial. The number one thing to support reflowering in almost all orchids is a temperature drop from day to night. Try putting them in a cold conservatory or the coldest room in the house. As long as frost does not form on the leaves they will not die.”

Specialist Orchid Nurseries
“The most important advice is to grow an orchid from a specialist orchid nursery and not one from a supermarket. The UK has some of the oldest orchid nurseries in the world and you can buy a beautiful, unusual plant for £20. I buy orchids from Burnham Nurseries and Odontoglossum orchids from McBeans Nursery, the last nursery in Europe to sell these orchids.

“You can see more gorgeous pictures and follow Luke’s passion in orchid growing on his Instagram page at @lukesorchidsandveg.