Seedlings in Flask – The most critical thing is to keep them cool. I have been told that because of the light source, heat builds up in the flask and will be about 10 degrees F warmer than the surrounding air. Excessive heat in phrags slows or stops growth. This is especially true of seedlings. You might try a room temp of around 68 F. I would think that lower would be fine. I am currently working with the light source at about 14″ above the shelf and running to 4′ flourescent bulbs for a 2′ x 4′ shelf.
Seedlings out of Flask – I have had a great deal of luck with seedlings out of flask in a number of media. Some that I would recommend are: live moss, perlite, or a mixture of Coconut shell fibre and perlite. In any case, I put styrofoam peanuts in the bottom to allow for drainage. Also, any of these media allow for a lot of watering. My experience with moss is that it will work exceptionally well, as long as you can keep it alive. With the perlite, compots are best and should be deep enough so that when the water drains out, the seedling’s roots can grow to the level of dampness that they like best. I tend to use pots over 4″ in height. With either of these, I water at least every second day. This is NOT the case with lindenii seedlings or crosses with lindenii. They are not water tolerant. So far, the best result that I have managed is using the perlite in a 6″ deep pot and watering only twice a week. Still the mortality rate was high. The more densely you plant the seedlings in the compots, the better they seem to do. These notes are from my own experience and each grower must discover the method that works best in his or her conditions. I have been successful in growing little plants just past the protocorm stage on without problem when growing in LIVE sphagnum moss. About the same light as for Phalaenopsis is good, but a cooler temperature is best.
***Please note that some species are unusual in that they are self-fertile. Various hybridizers have noted that some phrag species are capable of self-fertilization. This is often the case with schlimii and hinksianum and is almost always the case with reticulatum, boissierianum and czerwaikowianum (the last three producing pods with viable seed on every flower along a stem). It is possible to have a selfing take place prior to pollen being introduced from another plant which results in a selfing of the first parent. In my years of working with phrags, this has only happened once to the best of my knowledge. It is however a good thing to remember.***
Light – Mature plants can handle light pretty much to the degree that a cattleya can. This may seem like a lot and the leaves may get lighter in colour, but they do fine. I prefer to grow them with more intense light and with a longer day length. I live in Southwestern Ontario and our winter days are short here. I extend the day length in winter with supplemental lighting, so that the plants day runs from about 5am to 9pm. This is to keep them growing well in winter and also because certain species stop flowering in shorter day length periods (pearcei, ecuadorense, etc).
Water – I use rainwater whenever I can and this is almost always. I have used city water also, but the city water here is luckily of very good quality. I water either every day or every second day. Plants that I have sold people for in houses, I have recommended drenching thoroughly twice per week and this has seemed to work well.
Temperature – This is difficult to control in summer, but I try to keep the air temperature at or below 80 F. As mentioned, the plants do not like the heat. Caudatum and the others in it’s group become extremely susceptible to rot as the temperature climbs. I place those and my besseaes directly in front of the swamp cooler pads to try to keep them cool in summer. Most of the red tones are also weakened by warmer temperatures. The best colours that I get is in fall just prior to having the heat turned back on for the winter. You should never judge a plant for colour blooming during a hot spell. The colour may be vastly different during cooler times. I have also noted that the size and form of flowers of besseae are negatively affected by heat.
Air Movement – I don’t think this is generally mentioned nearly enough. Good air movement is critical. It reduces stress and relieves pockets of heat build up. It also dries leaves and crowns. I’m not sure of the mechanism, but my greenhouse has dropped to just above freezing for hours at a time and I lost only one plant as a result. The only reason that I can attribute for this success is the fact that I have lots of fans going.
Potting – I would recommend that all of the caudatum group be potted in small pots so that they do not remain too wet for too long. About the same size that is successfully used for paphs would likely do. For the others, I tend to overpot because I can’t keep up with their growth. I have used lots of different media with success. Currently I am using coconut shell fibre. I put a layer of styrofoam about 1/5 to 1/3 of the pot depth, covered by large chunks of the fibre (like I would use for the cattleyas) then a top dressing of fine fibre (not the brick stuff expanded). On top of this, I will add shreds of moss, so that it will grow to cover the top. This works well for me. The roots concentrate in the depth of the pot where the moisture content is most ideal. I water a great deal and have not found this material to break down easily so far.
Dividing – it is possible to grow a phrag division that has a stem going down with no active roots, but I do not recommend it. I am adding this item because of the general mistake of growers to divide mature plants into single growth divisions or to purchase single growth divisions. Being divided like that is too much strain on the plants and they may take years to recover. I have found that it is faster to grow a seedling out of flask to flowering size than it is to get a single growth division to the same point in many cases. I recommend a MINIMUM of two mature growths with new growth starting.
Fertilization – General health will be maintained throught proper culture, paying careful attention to the above details. In addition, I use various fertilizers. I have used simple fertilizers like ‘Miracle Grow’ and fish emulsion fertilizer. The latter I would not recommend unless you have a greenhouse (and one that does not vent in the direction of your neighbours!) Currently, I am using a Plant Product fertilizer in combination with Calcium nitrate as recommended by that firm. I go with the “weakly, weekly” routine. I feel that small amounts of fertilizer on a regular basis provide a consistent nutrient base while never shocking the plant unduly. Several larger firms have noted improvement by use of a ‘rest’ period of one month in the summer. I think that this may be due to the fact that the month’s time period allows for excesses built up in the media to be washed out. My own practice is to give a good rinse several times per year. This I accomplish by watering the entire greenhouse thoroughly, allowing it to stand half an hour and then rinsing thoroughly again with clear rain water (no fertilizer).