From: Clark Riley <clark_riley at qmail.bs.jhu.edu> on 1997.09.03 at 01:08:11(1151)|
Mail*Link(r) SMTP Dormancy triggers
In the case of temperate plants, including aroids, dormancy is often triggered
by a _COMBINATION_ of heat, light, and water conditions. Here in Baltimore,
last year's weather through the Summer was very nicely moist, giving a big
boost to the Konjac tubers. However, this Spring was consistently colder than
normal, so they and the Arisaema candida didn't emerge until well into _JUNE_!
Now we have had a long, hot, dry Summer. Though I supplemented their water,
I'll bet they sulk next year.
Despite the short growing season for these species, they can adjust by
changing the levels of chlorophyll, etc to recharge their batteries, as long
as there is plenty of available nutrients, including water. It seems most
hardy plants can adjust to variable growing seasons. Note how very dark green
foliage becomes in late Summer just before cool weather. Then, in a very short
time, the plants withdraw all the Magnesium, lose their chlorophyll and leaves
and go dormant.
In the case of tropicals such as titanum, the picture would be less clear.|
>From the meager literature on this group, I don't recall that the habitats
experience drought, they certainly don't experience cold weather, and
essentially no daylength variation. If there is a dormancy trigger, it
probably has to do with nutrients. Try changing your fertilizer for a couple
of rounds. Among Australian terrestrial orchids, it has been noted that they
often bloom after a fire. This can be simulated by giving a fertilizing with
extra Phosphorus (or maybe Potassium - I need to look that up at home). This
will "trick" them into blooming. Some orchid growers report that witholding
nitrogen will induce some reluctant ladyslippers into bloom, but often at the
expense of the plant!
clark riley, baltimore