Our Aerangis species were much admired at the British Orchid Show and for good reason. They are compact plants that produce impressive flowers and look particularly arresting when grown mounted to show of the lovely roots and generally pendulous habit.
Aerangis biloba is the Aerangis we find the easiest to succeed with. It is a species from Central and West Africa where it grows in deep shade in woodland up to 700m altitude. The large leaves are a deep green again indicating a plant that enjoys low light levels. The name refers to the unequally bilobed leaves ( a character it actually shares with many Aerangis species).
We grow the species warm, shaded and watered throughout the year. We grow the species mounted to show off the pendulous flowers and to allow the extensive roots to hang freely. We know others who succeed with the species in pots but we find that it can suffer from rots on a crowded bench.
The flowers are a sparkling white with a tinge of salmon pink when first open. The flowers have relatively short spurs (just 3-4cm) that contain the nectar for pollinating moths and plants are very free flowering. We find that this species is easy to grow from seed and de-flasks well straight onto mounts. It has flowered for us just two years from de-flasking and even produces the occasional kiki (little plant) from its roots.
I have just been to Lidl to buy flowers and was shocked to see a tray of dyed phalaenopsis plants (the dye is injected into the stem of a white phalaenopsis to turn the flowers blue, green and purple) with no indication to unwary customers that these plants are not what they appear. The advert online (above) again fails to mention that the flowers colour is fake. Why does this make me so angry? Is it the lack of respect for the natural plants? The hoodwinking of customers? The total lack of ethical trading? It is probably that I expected better of Lidl – that will teach me.
I have complained and I suggest everyone complains or how long will it be before the food is fake too? – or perhaps it is already?
At the British Orchid Show I promised visitors that we would summarise the way we grow our plants. I will produce a new tab for orchid culture once we have covered the topics of water and watering, temperatures and light, potting and propagation. Here is the first which is an edit of advice we gave in 2017.
A rainy day in November seems like the perfect time to talk about water. We are often asked about the water we use, and how often we water in the school greenhouses, so here are a few of our basic principles.
1.Rain water not tap water. We only ever use rain water at Writhlington. We collect more than enough from the roof of the greenhouse and store it in our 16000litre rainwater tank at the back of the greenhouse. Even in last year’s very hot summer we didn’t run out of rainwater as it stores about four months worth.
2. We pump our rain water into a 1000 litre feeding tank in the greenhouse where we add plant food and let the water warm up to greenhouse temperature.
3. We feed with a high nitrogen feed but at very low concentrations. Generally we feed with every other tank of rainwater. This allows for washing out any salt build up. We add half a jar of dry feed to 1000 litre which gives us a conductivity reeding of about 300-400 micro-seimens/cm. This is around 1/4 strength recommended on most commercial plant foods. We water heavily and so week feed often makes sense as well as avoiding a salt build up where water evaporates.
4. We water daily for most of the year but twice daily if the weather is particularly hot and dry (Usually from late May until the middle of July), Watering involves training a hose around the greenhouse from the feeder tank and ‘making it rain’ we focus more water on plants that are mounted, in baskets or noticeably dry. We avoid plants that we have identified as liking it dryer, are in a resting period or are clearly still wet from previous waterings. Plants in pots generally need much less water than mounted plants or those in baskets. Little pots need watering more than big pots.
5. We alter water availability with plant placing and compost selection. A good general rule is that the higher the plant is the dryer it grows. Firstly watering upwards is harder (especially if you are small) and secondly the higher parts of the greenhouse are hotter and dryer. We use a really open bark compost to give excellent drainage of our heavy watering and add dried sphagnum moss sparingly if we want a particularly damp compost (though too much moss risks the plant becoming dry and staying dry)
6. We never damp down. Damping down a greenhouse to keep it cool and increase humidity is widely recommended but we don’t. We find that damping down wastes water, makes the floors green and dangerous, keeps humidity too high and encourages rots in plants. We like our plants to have damp roots but live in airy conditions where they can photosynthesise effectively and that are comfortable for people too. Our recording of humidity in tropical forests has shown that it falls to 50% during the heat of the day in all the forests we have visited and so we do not worry about low humidity in our greenhouse.
This species has a real wow factor and for anyone who only knows the hybrid Cymbidiums available at garden centres a real surprise with its elegant pendulous dense spikes. I commend the botanist who gave it such an appropriate name.
The species is native to the Himalayas where we have seen it growing abundantly in forests above Gangtok (capital of Sikkim) as well as in North Sikkim and Arunachal Pradesh. Unfortunately we have always visited the Himalayas in the spring (great for Coelogynes) and so have not seen the plants flowering in situ but when not in flower can be identified by the large number of seed pods left from the many crowded flowers on the spike.
When we were last in Sikkim we took students from Takse School out into the forests of Fambong Lho (photo below) to identify orchids and this one of the species the students found. It grows in cool wet evergreen forest and is usually high in trees.
It is a medium sized but vigorous species and we find that it is well suited to growing in a large basket which we water daily and develops a layer of moss over time. We grow with a minimum temperature of 10C in Cool Asia but it could tolerate lower.
A level science students are carrying out independent research projects based on techniques they learnt about at Kew when we visited Jonathan Kendon at the Jodrell Laboratories.
Each student is working with seed from a different orchid species. They have investigated TZ testing for seed viability and are now assessing the amount of surface sterilisation needed for their seed sample. All work is carried out in laminar flow cabinets and the students are sowing seed with different bleach concentrations or bleaching times using an adapted syringe method using micropipettes to sow the seed.