Phal-a-Normal: Is this Phal Leaf Normal?
Although you almost certainly got your phal because of its flowers, the plant’s leaves are a good way to diagnosis the plant’s health and to spot any potential problems. So what is normal for a phal leaf? Here are some photos of "normal" phal leaves as well as a few of the common problems.
Ideally, the leaves should be smooth to the touch. As a good rule of thumb, the ideal color is a light, bright green. (think new, spring leaves on a tree 
)
Generally, if the leaves are a forest or dark green, the plant is likely not getting enough light. However, depending upon the plants genetics, it may naturally and healthily be a darker green as well.
There are other phals, such as Phal. schilleriana, whose leaves naturally have a gray mottling.
On fully grown plants, the leaves can vary from about three inches per leaf (on some species for example) to over twelve inches—so the leaf span can be anywhere from six inches to over two feet! Like human height, the leaf size is very much determined by the plant’s genetics, so don’t worry if your mature plant has small leaves. :-)
The plant will produce new leaves, one at a time on alternating sides. As the plant ages, it is perfectly normal for the plant to loose a bottom leaf. For example, this leaf is more than four years old, and will likely continue to yellow and then fall off all by itself.
Of course, because yellowing leaves can also be a sign of disease or other problems, a grower unfamiliar with phals could easily be confused. Sure signs that the plant is doing well and just normally dropping a leaf due to its “old age” are if the yellowing leaf is the bottom-most leaf, there is new growth on the plant and at least one pair of established, healthy leaves. For example, the same plant with the four-year old leaf turning yellow, also has this new growth and three additional healthy leaf pairs.
The underside of the leaf is frequently where the first signs of disease or infestation appear, so it is helpful to know what the underside should look like normally. Like the top, the underside should be smooth.
Again, there is some variation in the shade of green and some plants even have a purplish pigment to the underside.
Heat and Cold Damage:
Phal leaves can be damaged by either extreme heat or cold. These leaves were damaged by cold during shipping. The damaged tissue cannot be saved and should be removed with sterile scissors, and the remaining leaf edge should be treated with cinnamon or a fungicide.
At the opposite extreme, these seedlings were damaged by too much direct sunlight. They are pink because they literally have a sunburn. Again, the damaged leaves (or the damaged portions) cannot be saved and should be removed.
Insects and Disease:
Although phals are fairly resistant to disease and bugs, they do get little buggers from time to time. There are plenty of good posts in the forum identifying various bugs that can be seen, but sometimes the damage to the leaves themselves is the best clue. For example, damage from spider mites often appears as a silvering of the underside of the leaf or as what appear to be small pinpricks. For comparison, here is the underside of a leaf damaged by spider mites, and a photo of the underside of an undamaged leaf on the same plant.
So, if your phal looks similar to the "normal" leaves above, sit back, relax and wait for that next spike! If you need help identifying or solving a particular problem, post away--someone will be sure to have the answer. Happy growing!
