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 “Why
plumeria go dormant”
This is a subject that has attached to it, many falsehoods from some very
prominent and serious plumeria growers. We have never subscribed to the
theory plumeria go dormant to protect themselves from the cold. The
following is our reasons:
The fact is the plumeria grower’s biggest losses are during this period
of time in our area/latitude. So if plumeria go dormant as a protection from
cold, why are so many trees affected so adversely by the cold?
The answer is very simple: Plumeria in areas of their native habitat go
dormant when the day length shortens. Why? Because it is the “DRY” season in
this equatorial part of the world. If plumeria did not loose their leaves it
would continue transpiration, i.e. loss of water through the leaves leading
to total dehydration then imminent death.
Length of day is called “photo period”. So when the day length shortens
(i.e. photo period) in autumn and winter plumeria go dormant. Because of
plumeria genetics and physiology this dormancy is prevalent anywhere in the
world a plumeria is exposed to sunlight.
Periodicity in Plumeria
J. R. S. LAWTON & E. E. J. AKPAN
Department of Botany, University of Ibadan.
MURASHIGE has reported experiments in Hawaii which show that
Plumeria acuminata, a plant native to tropical America, exhibits a
deciduous habit which is controlled by day length. Day length in Hawaii
varies from about 11 h 45 min in January to about 14 h 15 min in June. In
Nigeria it is noticeable that the tree also exhibits deciduousness where the
day length varies (at Ibadan, 7° 26' N.) from 11 h 40 min in January to 12 h
35 min in June, about half the variation found in Hawaii. The
rainfall ceases at Ibadan about mid-November, however, and the dry season
continues until about mid-March. Isolated storms may occur within these
limits. In the experiments described here, rain fell only on the following
dates: December 7 (0.3 in.), February 27 (0.57 in.) and March 6 (0.07 in.).
In the last 10 days of March, however, the rainfall totaled 2.47 in. The dry
season therefore coincides with the period of leaflessness in Plumeria.
A number of Nigerian indigenous plants also exhibit periodicity in their
leaflessness.
- Murashige, T. , Physiol. Plant.,
19, 348 (1966).
- Njoku, E. ,
J. Ecol., 51, 617 (1963). |
- Njoku, E. ,
J. Ecol., 52, 19 (1964).
- Njoku, E. ,
J. West Afr. Sci. Assoc., 4, 99
(1958).
- Vegis, A. ,
Ann. Rev. Plant Physiol., 15, 184
(1964).
- Holttum, R.
E. , Symp. Soc. Exp. Biol., 7, 159
(1953).
Much study has been done over the past 50 years on various tropical
plants, succulents, cacti, true palms and plumeria showing their inability
to “harden off” prior to winter as do “woody evergreens, coniferous
evergreens and deciduous trees” native to our latitude. My personal
experience and association with the Southern California Nursery Industry for
over fifty years and growing plumeria for forty years has made this fact
very obvious.
The following science is an important fact about tropical plants:
“Plants from tropical and subtropical regions tend to have more
saturated fatty acids in their membranes than those from temperate regions
(our latitude). Plants which acclimate to low temperatures increase the
proportion of unsaturated fatty acids in their membranes.”
In Southern California and most latitudes in the US our plumeria become
very stressed during this dormancy period. The plant is genetically
expecting hot dry conditions but cold and rain is prevalent. This also is in
part the reason for what is commonly called "black tip". True tropical
regions do not suffer cold conditions therefore "black tip" as we know it
doesn't exist.
Plumeria cultivated in out of doors conditions should be in the “peak of
health” to best survive the conditions of dormancy in our latitude. This
becomes the grower’s responsibility. We at Kimis hope to be of help so
please read all the articles on our websites.
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