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Cattleya Culture - Part 3


The following article first appeared in the American Orchid Society BULLETIN Vol. 52, 1983 as part of a five-part series. While over 25 years old, it still remains an excellent resource for orchid growers. It has been edited to conform with modern taxonomic nomenclature and the availability of pesticides/insecticides and potting media.

POTTING CATTLEYAS can be the simplest aspect of growing or the most exasperating. It is certainly the most difficult about which to write! While we have already discussed much of the "why" we pot cattleyas as we do, here we will talk about the "how" and "when".


We learned earlier that most of the Cattleya alliance species grow as epiphytes in nature. Their roots are largely exposed and subject to periodic drying. Much of their moisture requirement is met by the frequent, brief rains of the tropics. Some is met by the nightly dews which are absorbed by the spongy, velamen layer of the roots. It is the plants' love of good root aeration that leads us to use the relatively coarse, free-draining media that we do.

Osmunda, hapuu, fir bark, charcoal, and many other materials share the desirable characteristics we look for in cattleya potting medium. One or another may work better in a particular area or for a particular grower, but all have relative merits and drawbacks. What works best for you and is cost-effective is the "best medium". It may not be so for others. An important point here is to give a fair trial to any new medium with which you are experimenting. This means growing a year, preferably two, in that medium before a final decision is reached. (Of course, if immediate, severe adverse reactions are noted, it is wisest to terminate the trial!) Because of the relatively slow responses of cattleyas, it often requires some months for the plant(s) to adjust to a new medium and begin to display any adverse or desirable reactions.

Leo Holguin tells a very good tale that illustrates this point. Many years ago, a hobbyist came to him for advice about mixes and potting Apparently, his plants were doing poorly, indeed, declining. Leo asked him what potting medium he was using. The hobbyist replied that he had recently repotted all his plants into new medium "Z", (Not a good idea in the first place: never experiment with a new medium on all your plants before trying it on a few, first!) after being dissatisfied with their performance in medium "Y". Leo asked him how long he had used medium "Y". "Oh, about six months or so", he responded. "I tried it because they didn't do well in medium 'X'." This sequence had apparently been repeated every 6-8 months with medium "W", medium "V", medium "U", etc. Leo suggested that the hobbyist give his plants a fair shake in medium "Z" for at least two years and see how they did. When the gentlemen returned two years later, he had learned his lesson, as his plants were finally recovering and growing well.

Especially in these days of shortages, it is well and good to experiment with new media and materials. But be scientific and use common sense! It is wise to evaluate a medium thoroughly before deciding to try it on your plants. Factors to consider before trying a new medium include convenience. Is it easy to use? Is it readily available locally, and is liable to remain so? Finally, is it reasonably priced? If you can answer these questions to your satisfaction, give the medium a try. Remember, though, to use it only on a few of your expendable plants at first. This will enable you to evaluate its performance fairly without sacrificing a good plant.

The basic media types were discussed earlier under the fertilizer section. The vast majority of cattleyas in this country are grown in fir bark and/or tree fern mixtures. These will provide freedom of drainage and aeration if appropriate, commercially prepared fertilizers are also readily available. Here on the west coast, we use fir bark almost exclusively, often with the addition of redwood bark. Habit and availability have led to this practice. In the southern and eastern areas of the United States, also in Hawaii, tree fern is used more extensively as it is more readily available [Editor's note: tree fern is now becoming more difficult to obtain and at reasonable prices.  As a result more plants are being grown in alternatives like Alifor, lava rock, Stalite and other inorganic media].

I want to stress here that the medium alone doesn't grow the plant! The grower does. This incorrect supposition can often lead to misunderstandings. "Boy, that mix sure works super for Joe down the street! I'm gonna try it!" If the medium doesn't grow plants like Joe's it isn't Joe's fault. Joe simply grows his plants well in his potting medium. Observation of your plants' growth habits is what will make you a good grower, not just the medium or fertilizer or whatever. Beyond helping to determine light levels, watering levels, or possible necessity of pest or disease control, good habits of observation are an absolute must in deciding how and when to pot.

Remember our friend from the first article and how his favorite plant died after he repotted it? He lacked good observational habits. Otherwise, he might have noted that the plant in question was not at a point where it could safely be repotted. Knowing when to repot is probably the most difficult part of growing cattleyas successfully. It is encouraging to note, however, that time and experience have provided us with more insight than the early growers had.

Before the advent of the large-scale growing of hybrids, Cattleya species by the tens of thousands were imported for cut-flower use. While many of these species grew easily and prolifically under cultivation, a few were intractable, at best sulking and refusing to grow if not potted at just the right time. Cattleya warscewiczii (C. gigas) and C. dowiana are two good examples, as are the bifoliate species Cattleya amethystoglossa (especially the "blue" or coerulea forms) and C. guttata. The mere mention of these and other Cattleya species can still strike fear into the most experienced grower's heart. Observation was the saving grace with these difficult species. Over time, growers noticed that there was a very particular time of year (and stage of growth) at which a given species would initiate most or all of its roots for the year. If the plants were potted at just this time, they took off and grew happily. If not - no more plant!

While most cattleyas grown today are very complex hybrids, and exhibit little or none of this fussiness, problems can still occur if common sense is not used. Basic knowledge of the species behind a hybrid is important as this background determines to a large extent the plant's preferences.

Common sense dictates that a plant in bud should not normally be repotted. Not only will the flowers be poor, but the plant's strength will be sapped by the flowers. If the plant must be potted while it is in bud, it is best to break off the buds to protect the plant's future productivity. A plant with mature leads that have finished their rooting is another poor bet for repotting. Waiting for fresh root tips to appear or the beginning of a new growth will help to ensure that plant's speedy recovery from the shock of repotting.

As one grows and learns from his or her cattleyas, a sense of when to repot will develop. Observation of the plants throughout the year helps the grower to learn at what growth stages a particular plant, or type of hybrid, will "throw" roots. Once this is learned, it is best to repot just before the roots are to be initiated. This added precaution will prevent the newly emerging, tender root tips from being damaged or broken. Many times, if the root tips newly emerging from the base of the growth are destroyed, the plant will not grow any new roots until another new growth is formed.

Knowing the species background of hybrids is important, especially in those hybrids relatively close to species (primary or secondary hybrids) or which have a great deal of certain species in their background. For instance, yellows can be more demanding than whites or lavenders as there is usually quite a bit of Cattleya dowiana represented in their breeding. For this reason, extra care must be utilized with most yellow hybrids to pot only when there is evidence of root activity, preferably in the spring or early summer. This also holds true for bifoliate-type greens as they are heavily influenced by Cattleya guttata and/or C. bicolor. It should be stressed that these are examples but are not the only two things one need look for. If you have noticed that a certain plant or plants exhibit(s) a failure to establish well after potting, close observation can often lead to a better understanding of why the plant(s) may be acting that way.

FIGURE 1. Newly emerging roots indicated that now is the time to repot this overgrown cattleya.

Because it may be difficult to visualize the stages of rooting behaviour (and, not coincidentally, being difficult to write about), this series of illustrations and explanations should help to clarify the subject.

This obviously overgrown plant in FIGURE 1 shows the rooting behaviour of many standard Cattleya hybrids. Note that the first pseudobulb over the pot edge is mature and fully rooted; it has probably already flowered. The roots are healthy but have not branched. The second pseudobulb over the edge is maturing (note that the sheathing basal leaves/bracts are still green) and is just beginning to show renewed root activity at its base. This plant should be potted now!

There are several other interesting features illustrated here. The roots on the mature bulb are healthily growing in air like aerial roots. Although they will branch freely all along their length, it is best to trim them when potting to approximately four inches. As these roots have matured in air, they will probably die when confined to a pot. Four-inch length allows for anchorage and possible branching without excessive potential for rot in dead tissue.

This picture also shows what we call the "stairstep" habit of many unifoliate species and hybrid cattleyas. The plant appears to be climbing out of its pot. While we will be discussing this habit at greater length later in the article, this habit greatly affects how a cattleya must be potted. The division must be leaned forward so that the rhizome is level with the surface of the mix. A plant potted in this way will tend to grow along the surface of the mix, rooting as it goes. If the rear portion of a division is sunk into the mix so as to keep the bulbs straight up and the new growth at surface level, the plant will tend to climb right out of its pot. Not only is this unattractive, the fresh root tips will not penetrate the potting medium quickly, if at all, leaving them exposed to insect or physical damage. So, no matter how unnatural it may seem at first to have the bulbs leaning forward, potting in this way really will help your plants to grow better in the long term.

FIGURE 2. Though the new roots of this
cattleya are well on their way, it is not too late
to repot.


FIGURE 2 shows a spring-flowering Cattleya hybrid approximately two weeks after flowering. The roots on the lead bulb have begun to grow and this plant may now safely be repotted. Ideally, it should have been potted immediately after the flowers were cut two weeks earlier. Extreme caution will have to be exercised to avoid damage to the elongating roots.

Potting time is also an excellent time to clean up the plant, removing dead sheaths and old flower stems. Good sanitation is an important part of growing orchids well. Besides, the plants look better when they are cleaned and cattleyas out of flower need all the help they can get to look attractive!




FIGURE 3. Now is not the time to repot this
plant, as the roots of its newest growth are fully



It is too late to pot the plant in FIGURE 3! This is another spring-flowering hybrid and was photographed about a month after the flower had been cut. Note that the roots are almost fully made up and new growth is beginning to break. We like to wait for the new growth to make up at least half-way before potting as it is all too easy to break off a young growth while tamping in the mix. While breaking a new growth is certainly not fatal, it is still a set-back to be avoided where possible.


FIGURE 4. Failing to repot when necessary resulted in this tangled mess of new growths and roots.

"The bulbs are at the edge of the pot, but the mix is still good and it's growing so well! Maybe I'll just wait till next year to pot this one." Here, in FIGURE 4, is what happened. Saving a little work this year can lead to a major task next potting season. Pictures like this make even experienced potters shudder. When this type of tangling goes too far, entire leads must sometimes be sacrificed so that the division may be properly potted. We have even had new leads grow straight down over the pot's edge and through the slatted wood bench to flower underneath! The important lesson here is never to put off until tomorrow what is best done today!

FIGURE 5. Properly positioned and staked, this Cattleya division should re-establish quickly.

Here in FIGURE 5 we have a properly potted division of a mature Caltleya hybrid. The back of the division is against the rim of the pot and the front has plenty of room for two years' growth. Notice that the bulbs lean forward slightly, allowing the rhizome to be level with the surface of the potting medium. The bulbs are secured with string, steadying the plant. An unsecured plant can damage its tender, new root tips against the medium if it rocks while being moved or watered. The new growth can be seen emerging at the medium surface and is beginning to orient itself properly upright. It is in perfect position to root directly into the fresh medium. The vital label is in place and this plant is ready to go back into place in the greenhouse.

FIGURE 6. Because this division was incorrectly oriented, one month after repotting its new growth is entirely above the medium.

An improperly potted division as in FIGURE 6 will show symptoms early on. Although the mature lead bulb rooted into the mix, the developing growth is well above the surface of the mix. This photo was taken approximately one month after potting. The combination of incorrect orientation and the stairstep effect will result in the leads growing farther above the mix so that in two or three years, when the plant again requires potting, the newest lead may be four inches or more above the surface of the potting medium. Note also that the back bulbs are partially buried. This is a potential problem area for rots as the base of the bulbs may never entirely dry.

FIGURE 7. New leads whose bases are level with the mix will root firmly soon after repotting.

This division in FIGURE 7 had been potted (correctly) approximately one month before this photo was taken. The new leads emerged at the mix surface and are now beginning to orient themselves upright as they grow. Beginning root activity can be seen at the base of the new growths. Some temporary shrivelling of the older bulbs is normal but they will plump up quickly as new roots form.

FIGURE 8. Little more than a month after repotting, the roots of this new growth have penetrated the potting mix.


FIGURE 9. Recently repotted, this Cattleya
seedling is beginning to take root.


Above, the potting medium has been cleared away from around the base of this four-to-six-week-old division in FIGURE 8 to illustrate how the new roots quickly penetrate the medium. Although most cattleyas root when their pseudobulbs are at least half-mature (and often also immediately after flowering), root loss through potting can encourage rooting, as is the case here.



FIGURES 9 and 10 show the rooting behaviour of young seedlings. FIGURE 9 shows a recently potted seedingjust beginning to root. The slight dehydration in evidence is remedied as the plant establishes.




FIGURE 10. Vigorous rooting three months
after repotting indicates this Cattleya seedling
is becoming well-established.

The seedling shown in FIGURE 10 has been potted for about three months. Well on its way to being fully established, green-tipped, clean, white roots are growing profusely into the fresh mix. Vigorous rooting, as illustrated here, is just as satisfying to many experienced growers as flowering!

All of the experience and good intentions in the world won't help you with certain varieties. Many older cultivars, with notoriously poor growth habits, have passed out of cultivation simply because they grew too large, or poorly, to be considered worthwhile. Distance between pseudobulbs, pseudobulb size, and liberal production of multiple, new leads are all important considerations in this energy- and space-conscious age.



FIGURE 11. The elevated position of these new growths is a sign of an incipient "stairstep" growth habit.

There are still many clones in cultivation that have some or all of the above-mentioned drawbacks but are grown either because of their intrinsic antique value, or because they are good parents. The Rhyncholaeliocattleya (Brassolaeliocattleya) Norman's Bay line is a good example of this type. FIGURE 11 shows the beginnings of the worst trait of this line; the extreme, stairstep growth habit. The lead bulb (on the right) has initiated two new growths, an excellent habit, but the lower new growth is approximately 1 1/2 inches above the surface of the mix and the upper is approximately 2 1/2 inches above. Difficult to pot at best! Note here, as well as FIGURE 12, that there is one to two inches between pseudobulbs. Plants with this habit leap out of their pots very quickly!


FIGURE 12. Two years after repotting, the extreme stairstep growth habit of this Cattleya
hybrid has produced this unwieldy plant.

FIGURE 12 shows the stairstep effect in a more advanced stage. This plant was potted two years ago. There are already four bulbs on one rhizome which are over the pot edge. This obviously renders the plant difficult to keep upright, to bring into the home to enjoy or to keep out of its neighbors' pots! When purchasing plants, look for this behaviour and avoid it where possible. Unless, of course, you just can't resist the flower!

FIGURE 13. A stairstep growth habit manifests
itself early in this seedling's development.

The stairstep effect, generally less severe in FIGURES 13 and 14 than in FIGURES 11 and 12, can be observed very early in an orchid's life. In FIGURE 13 we have a seedling approximately 30 months old and ready for its first pot after being in a flat. We can see that it is climbing already.

FIGURE 14 shows the proper, if somewhat unnatural-looking orientation of the plant to a pot. Although the bulbs lean radically, the rhizome is level. The bulbs can easily be tied up (see FIGURE 5) or left. The new growth will develop nice and straight, assuming that it has had sufficient light.

After all these "do's" and "don't's", the beginning grower might understandably approach potting his cattleyas with some trepidation. This is not the intention of this article. While cattleyas are certainly not the easiest orchids to pot properly, they are in general not all that difficult.



FIGURE 14. To combat this tendency to climb,
an almost horizontal orientation of the seedling is
necessary in repotting.

Two points should be remembered: first, it takes just a little extra time and effort to do a good job; and the extra time will be repaid many times over by the better growth of your plants. Second, in endeavoring to cover all the bases, I may have implied that the potting of these plants is quite complex. For 95% of the cattleyas you will ever grow, potting is not difficult at all. To help readers look out for potential problems, the problem areas need to be enumerated. Few people need or want help with their easily-grown plants; they want help with their problem plants.

At this point, advice given earlier should be repeated. That is, don't be afraid of your plants! They want to grow and flower. All the grower need do is to be aware of and to be responsive to their needs. This implies clear-headed, positive observation and good judgment.

The next article in this series on the culture of cattleyas will deal with problems of pest control. Armacost & Royston, 3376 Foothill Road, Box 385, Carpinteria, California 93013.