Pleione Cultivation - Part 3
5. Watering Pleione
Pleiones are watered from spring through summer to autumn and then kept totally dry while dormant in the winter. The critical time is early in the season. The roots usually start to grow more or less as the flowers fade and at this time it is important to give only a little water - the aim is to keep the compost only-just damp and make the newly-emerging roots go searching for moisture. If the mix is too wet at this time there is a danger the new roots will rot. Once however the roots are well established (often evidenced by rapid leaf growth) watering can be increased substantially. Pleiones come from areas which get the summer monsoon. As long as your mix is very free draining, it is difficult to give them too much water once they are actively growing.
It is best to use rain water, soft tap water or water produced by reverse-osmosis, but this is not so critical for Pleione as for many other orchids and they will tolerate hard tap water. If possible, keep them open to the weather in summer so they can be rained on. They love it! While I still had a small collection I used to take the roof glass out of the glasshouse during summer so the rain could fall on them. It also kept them cooler.
As days shorten in the autumn and growth slows, reduce watering. When the leaves start to go yellow it is time to stop watering altogether and allow them to completely dry out. The leaves will go brown and finally fall off and the pseudobulbs enter their dormant phase.
Pleiones are watered from spring through summer to autumn and then kept totally dry while dormant in the winter. The critical time is early in the season. The roots usually start to grow more or less as the flowers fade and at this time it is important to give only a little water - the aim is to keep the compost only-just damp and make the newly-emerging roots go searching for moisture. If the mix is too wet at this time there is a danger the new roots will rot. Once however the roots are well established (often evidenced by rapid leaf growth) watering can be increased substantially. Pleiones come from areas which get the summer monsoon. As long as your mix is very free draining, it is difficult to give them too much water once they are actively growing.
It is best to use rain water, soft tap water or water produced by reverse-osmosis, but this is not so critical for Pleione as for many other orchids and they will tolerate hard tap water. If possible, keep them open to the weather in summer so they can be rained on. They love it! While I still had a small collection I used to take the roof glass out of the glasshouse during summer so the rain could fall on them. It also kept them cooler.
As days shorten in the autumn and growth slows, reduce watering. When the leaves start to go yellow it is time to stop watering altogether and allow them to completely dry out. The leaves will go brown and finally fall off and the pseudobulbs enter their dormant phase.
6. Feeding
Pleiones need to be fertilised to build up the pseudobulbs for flowering the following year. They like regular but weak feeds with a liquid fertiliser. Feeding should start once the leaves start to grow quickly - often late May with me, and continue until the autumn. I have used various feeding regimes and many different brands of fertilisers over the years. I don't think it makes too much difference as long as you do feed them regularly. In my current regime I use the "Miracle-Gro" brand of fertiliser:
Miracle-Gro fertiliser
This has an N - P - K analysis of 24 - 8 - 16 plus trace elements. I give this once a fortnight at about one third to one half of full strength. In the alternate weeks that they don't get this, I give them some liquid seaweed extract ("Maxicrop") again at one third to one half of full strength:
Maxicrop Seaweed Extract
For measuring fertiliser strength accurately, a conductivity meter is a very useful instrument:
Conductivity meter
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Orchid growers often invest in such an instrument because many orchids are very sensitive to being over-fed. Measuring the strength of your fertiliser solution accurately helps to avoid this possibility. These meters may measure in units of "parts per million" or "microsiemens". I am most familiar with the latter. Whenever I make up a fertiliser solution for the pleiones I aim to make it produce a reading of 600 to 800 microsiemens on the meter. For comparison, a full strength solution may read 2000 to 2500 microsiemens
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7. Light, Air & Temperature
When grown under glass, pleiones need to be shaded from direct, bright sunshine. A shade cloth giving about 50% shade is ideal, or the glass can be painted with a traditional style whitewash. They also enjoy fresh air, so provide plenty of ventilation - a fan is very useful to give some air movement. They prefer cool temperatures, preferably below 25 centigrade though they will tolerate higher temperatures for a while. Outside, they can tolerate full sun but it is more usual and advisable to provide somewhere semi-shaded, for example in the shade of a tree providing dappled light. You may also need to think about some protection from birds and other wildlife, (not to mention the footballs coming over the fence from the neighbours' kids!); growing inside a fruit cage would be ideal. Outside they are also more vulnerable to slugs & snails which love pleiones!
8. Exceptions - species that require different treatment
The treatment outlined so far applies to the vast majority of both species and hybrids. But a few require something different. Pleione maculata, Pleione praecox and their hybrid P. x lagenaria are autumn flowering. These, along with many autumn & winter flowering hybrids, have a rather shorter rest period and need to be kept warmer during this time - a minimum of 10 centigrade for P. maculata though P. praecox can go colder than this. They barely have a dormancy and start to grow new leaves very early - often before the end of the year - and new roots too. Despite this new growth, do not be tempted to give a lot of water - keep them a little moist - perhaps mist them occasionally and perhaps stand the pot in a few millimetres of water for a few minutes to give some moisture at the bottom of the pot for the new roots to go heading for. Don't start regular watering until you are sure the new roots are well down the pot. P. maculata in particular also likes to be kept warmer in the summer with plenty of humidity too.
Pleione saxicola is another autumn flowerer recently introduced to cultivation. It grows a lot of new root very early in the autumn, before even the flowers die down. It is probably better to keep it moist throughout so these roots don't die - though I have tried treating it like any other normal species and it grew OK.
Pleione coronaria, P. hookeriana and P. scopulorum all have a longer, cold winter and a shorter growing season than other species. These species do better if kept cold for longer in the winter, using a fridge if necessary. I suggest keeping P. coronaria and P. scopulorum in the fridge until around early March and P. hookeriana until late March. Keep an eye on them though and take them out if they threaten to flower earlier than this. Also, P. scopulorum unlike other Pleiones must not be allowed to dry out completely during dormancy or it will shrivel and die.
Pleione forrestii also I believe benefits from a long, cold dormancy and should be kept cold until early March if possible. However, this one more than the others has a tendency to flower early and if the buds are clearly developing quickly, remove it from the fridge. It might be worth noting that while cold may delay flowering it will not necessarily prevent it altogether - plants can achieve full flower in the fridge in the dark!
Finally it must be said that some of the species, particularly all those mentioned above, are not easy to grow and we still have much to learn.