Growing Paphiopedilums By Gary Dobbs
I class myself as a novice having only grown paphiopedilums for around 3 years. However, my results are speaking for themselves as more of my orchids are receiving awards at various shows. Simply, I gathered a significant amount of information including plant culture, greenhouse conditions and feed. I then experimented with this over a number of years deciding what best suited my plants through close observation. Obviously, some plants benefitted more than others; but the majority I have found seem well suited to the conditions I am presently providing. There have been a few fatalities along the way but most are exceeding my expectations.
Paphiopedilums are native to India and other parts of Asia including Indonesia, South China, Burma, The Phillipines, Solomon Islands and New Guinea. They grow in highlands in some regions as well as lowlands. Some are found growing in soil and leaf litter, others on limestone cliffs and rocks. However, all of them require the basic nutrients to grow well, eg calcium etc, and I feel they receive this in similar quantities from their respective environments.
Initially, paphiopedilums can take a few years to reach maturity and flower, especially species like rothschildianum, so an element of patience is required. A point to note is that I have now decided to concentrate on acquiring established plants with strong growths and healthy root systems, and either those approaching blooming size or ones that have previously flowered. I have found that the established plants seem to adapt better to re-potting and the new culture. The small seedlings are very slow growing so care must be taken with the conditions and feed until a certain size is reached. Also being smaller and weaker makes them more susceptible to problems and diseases.
To provide the intermediate to warm conditions for my mainly multi-floral paphiopedilum collection, I decided to purpose build my 3 x 3 m greenhouse. Solid brick walls on 2 sides, with large double glazed units and 28 mm polycarbonate roofing were all used to provide an airtight structure, helping with the control of temperatures and more so, heating costs. Equipment including a dedicated thermostatically controlled 3kw heater/fan, extractor fan and hydrofogger all contribute in providing the essential factors needed for optimal growth. Circulation fans are also important and they are running 24/7.
As I also live in an area with extremely hard water, it was also felt that a system providing reverse osmosis water would ensure the plants received the purest water and only the feed/nutrients I provided.
I class these orchids in the intermediate to warm range therefore growing at a minimum of 12c at night in winter and summer. The maximum is raised from around 18c during the day in winter to 24c throughout summer. However, during extremely warm periods, there is a thermostatically controlled extractor fan that is set to help cool the greenhouse and avoid plants shutting down. Vented windows also help in the cooling process and in turn help provide an essential circulation of fresh air.
I prefer to grow my paphiopedilums within a humidity range of between 65 and 80% which is maintained throughout the warmer months by a hydrofogger. This is required less in the autumn and winter where humidity naturally remains higher especially at night; thus hardly comes on. The air needs to be fresh and moist, but not saturated, and on balance with light and heat provided by the greenhouse. The air also needs to be well circulated by a number of circulation fans to avoid becoming stale.
Paphiopedilums grow in a variety of light levels, some in shade, others in strong light, such as philippinense. I attempt to provide approximately 1500-2000 fc for my plants controlling this through the addition of shading. My observations are that more light provides better quality flowers but with paler foliage, and also strengthens the plant making it less susceptible to diseases. The point to note is that the grower should experiment with their plants to ascertain where they perform best and grow them accordingly. This may take a few seasons as each grower has different conditions. Paphiopedilums are not fast growers and even though the plants can be moved around, it may be beneficial to leave them settled in a set position for a while.
Watering and Feeding
In general, most habitats of paphiopedilums are subject to monsoon conditions with plenty of air movement. I prefer them to dry rapidly after watering as the roots can easily rot should they stand in a waterlogged medium for any length of time. The plants require a basis of fairly high humidity, a porous growing medium and good circulating fresh air. As I only use pure reverse osmosis water, my plants will only receive the feed I provide. They are fed slightly acid around the 5.8 to 6.2 range. Feed strength is measured in microsiemens every watering by means of a pen with the reading being approximately 500-600. I have now been using Akerne’s Rain Mix (MSU feed) for a while now on all my orchids with excellent results. I have found it has all the necessary macro and micronutrients as well as calcium and magnesium for optimal growth. I have found that with this feed ratio of 13-3-15, it also provides the necessary nutrients of N-P-K for my plants to grow strongly and initiate flowers without the need to use bloom and growth feeds at certain times of the year. I treat each plant individually as they all dry out at varying times so therefore feed them at every watering “when they need it”. The medium needs to be kept moist, but not waterlogged and also avoid letting it dry out.
Pests and Diseases
Paphiopedilums, like any other orchids, will suffer attacks from aphids, mealy bugs, scale, mites, thrips, slugs and snails. Regular inspections and cleaning of the leaves is a process I regularly undertake. Any first signs are treated immediately, normally with Provado Ultimate Bug Killer or Liquid Alcohol. I also use a solution of Physan 20 fungicide as a preventative applying on a monthly basis.
One of the most fatal diseases to paphiopediulums is erwinia or brown rot which normally occurs through cuts or within the crown of the plant. If left untreated, it can spread and desimate the plant in days, leading to in some cases, the death of the plant. Removing the plant to an isolated area is also recommended as the disease can spread and therefore the whole collection may be at risk. Again, a strong solution of Physan 20 applied to the whole plant may help, but not guaranteed and the infected area or growth may have to be completely removed.
Potting mixes are a personal choice and after being fairly successful over the last few years with CHC (coconut husk), I have now commenced using a new bark medium that is showing very good results. I intend to assess this over the next 12 months but I am fairly optimistic and confident that the results will see me using the medium for the foreseeable future. As well as being an excellent medium, it also has a slow breakdown time of between 2 and 3 years, therefore avoiding the necessity of re-potting. As stated previously, the medium for paphiopedilums needs to be well draining, but kept moist to avoid damage to the roots. In addition to the bark, I also add small amounts of coarse perlite and small charcoal.
To help with paphiopedilum culture, it would be very beneficial to understand the individual plants habitat and growing conditions. Even though it may be extremely difficult to duplicate these conditions, you may be able to provide the plants basic requirements as a starting block and experiment further. One last piece of essential advice I feel is to obtain the book “The Paphiopedilum Growers Manual” by Lance A Birk. This has been invaluable and I can only say that it provided a significant amount of important information and observations that helped me in my paphiopedilum culture.