Pachypodium Care (con't)

(A photograph of a cactus emailed to me which I believe belongs to the genus Pachypodium)

The precursor to this blog entry is a post from last August which I made a link to here.

Questions:
Returning to our exchange of e-mails last year, here is an update on my columnar whatsit.
It remained dormant and leafless all during the winter. A month or so ago it began putting out leaves from all columns and I gave it one dose of Miracle Grow in its every-three-weeks watering.
It now has leaves from the top of each column and seems to be putting out more.
BUT once they come out at the top of the tallest (about 42" tall) they shrivel in curls, although others seem to be pushing out behind them.
What might be happening and what can I do?
Is the stalk simply too tall? Can the water not get up that high?
Are there bugs on that stalk and not on the others (I can't see any and am reluctant to spray it since the dosing last year seemed not to do anything good.)
Could it use more feeding?
Should I just forget about it and admire the rest?

Answers (for now):
As I said in a previous email I believe that your columnar whatsit is in the genus Pachypodium. In short, I know of no other cactus (at this point in my career) that produced those tufts of almost tropical looking foliage atop their spiky stems.

I've revisited a few references here in the library and these are my thoughts regarding your questions:
The stem is not too tall for water to be able to easily travel. Cacti can grow to well over 20' in their natural habitats and do just fine so we can rule that out. Plants vascular systems can allow water to be transported up and down hundred of feet in fact. I still refer to an article I read years ago on giant redwoods of the west coast where they talked about how, at 300 feet above the soil surface, water transport became significantly more difficult, often leading to the tips of these giants being sheared off by coastal storms.

That being said, one concern might be if the tallest stem is being hit with any kind of dry air. Is there a heater or fan that blows on the tallest stem at all? Here in the office I try and keep plants as moist as possible but sometimes if they are in the direct path of a ventilation or heating system that can dry plants out very badly regardless of my efforts. Even though it sounds kind of crazy, I suppose you could mist the tallest leaves and see if they continue to be deformed. Cactus often thrive in dry climates, hence "sounds kind of crazy", but our apartments can get so dry this time of year before we open them up to the summer humidity outside.

Since the issue is isolated, I might guess that it is an insect issue. There are plenty of mites that are not easily visible to the naked eye, but I do not know of any that target cacti, nor do the references suggest any in particular. Red mites and spider mites have been found to attack some cacti, but those two you can usually see. I would probably spray the top, deformed leaves with an insecticidal soap just to be safe. Isolate the plant before spraying if you are worried about spraying any other plants or furniture in the same area. If you have an outside space where you can situate it, perhaps the fresh air will help it out. Of course, I'd avoid leaving it out during any major rain, like we might get tomorrow.

I certainly wouldn't fertilize it any more than you already are.

Hope this adds at least a little new food for thought. Chat again soon.