One characteristic of some Dendrobium species is that they have the
capacity to produce plantlets from the meristematic tissue that lies in the
form of small buds along the sides of the canes of the adult plants. Most of the year these buds lie dormant, but
if they are activated by hormonal changes in the plant they can turn into
floral stems or into little plantlets.
In the hobby these little plants are known as keiki, this is the
Hawaiian word for baby. I will use the term
keiki to refer to this form of propagation on the rest of this article. Keikis are plantlets produced vegetatively by
the mother plant, it is an asexual type of reproduction which means that the
little plants will be exact copies of the mother.
The frequency of keiki production varies
wildly in the Dendrobium genus. Some species will never, or only very rarely
produce them, I have yet to see a keiki in a plant of Dendrobium farmeri or Den.
secundum. In other cases some plants
will produce keiki and others of the same species will not. This is my experience with Den. harveyanum, one plant has produced
several keiki while another has never produced them. Some species will almost always produce one
to a few keiki from older canes, an example of these are Den. anosmum, Den. cucullatum
and Den. primulinum. In the extreme of keiki production Den. crumenatum and Den. kingianum produce them frequently and sometimes abundantly.
There are several circumstances
that can stimulate the production of keiki.
A relatively common occurrence is the production of keiki instead of
flowers. Normally canes will not produce keiki in their
first year, before they have bloomed. If
a mature cane produces keiki instead of flowers when its blooming season comes
around, this means something has disrupted the sequence of metabolic processes
that produce the hormonal changes that turn the resting vegetative buds into
floral buds. In Dendrobium descended from Den.
nobile and related species, if the
plant is given a fertilizer with a high nitrogen content during the latter part
of the growing season or the resting plant experiences too high temperatures,
this can “short circuit” the blooming response and then it can either not bloom
or it can produce keiki where blooms would have been expected. I
have seen plants produce keiki all along the cane where flowers should have
been. In rare cases a plant can both
produce keiki and some flowers. A few
days ago a friend showed me one of his Den.
nobile hybrids where the plant had produced keikis instead of flowers and
then some of these keiki had produced a single flower from the tip of their
tiny canes.
In many Dendrobium species the sudden production of keiki by a plant on
canes young and old is a signal of significant root loss. I have frequently observed this on Dendrobium species from the Spathulata section and on hybrids
descended from Sphatulata/Phalaenanthe
section. These hybrids are produced by
the millions and are commonly sold on Walmart, Home Depot and other stores
because they travel well and their flower sprays last for weeks in good
condition even in hot weather. The
problem with these Dendrobium is that
most the people that buy them often now virtually nothing about their growing
needs. When these orchids are repotted
they are frequently put in dense bark mixes that are kept wet. If the mix is so dense and soggy that it
doesn’t allow oxygen to reach the roots, the roots die. The one common indication that the roots
have died is the complete defoliation of the plant. That is all canes, young and old shed their
leaves due to the loss of the capacity for water uptake. By the way, it is normal for the older canes
of many types of Dendrobium to be leafless,
it is abnormal for a cane of the year to lose their leaves, particularly in the
evergreen types that are common in the retail market. If the plant is cared for well, it might
start growing in its season and if it has a number of healthy canes it can even
produce a reasonably large mature growth that will in time produce a new root
system. But if, the loss of roots has
been accompanied with the loss of the lower vegetative buds, the plant can
produce keiki from the top of the canes.
I have seen plants that have lost the lower vegetative buds because the
owner buried the base of the stem under the potting media and the new growths
have succumbed to rot. By the way,
sometimes a Dendrobium will produce a
new cane from a bud that is located slightly higher in the stem than previous
growths, this is not a keiki, as canes produced this way can develop normally
to full size. This sometimes happens
when the buds at the base of the stem are lost.
Keiki produced at the top of the
canes varies hugely in quantity and quality depending of the ancestry of the
plant. I have an antelope Dendrobium (of
the Spathulata section) called Percy’s Passion.
This plant lost its roots and produced a single very large keiki that is
for all purposes a small adult plant.
This keiki has even bloomed with a substantial inflorescence while still
attached to its mother’s cane. In these
cases these keiki can be cut from their stem, potted and treated as an adult
plant, they don’t need any special considerations.
On the other hand some plants
will produce tiny keikis at the very tip of the canes. These keiki are typically one to two inches
long and depending on the parent species, can have a substantial quantity of
roots or almost none. Keikis that are
smaller than two inches are a special case. They are much more fragile than
those that are over two inches and might not survive being detached from the
cane. If they have few roots they will
need care that addresses their particular needs and it may be more than the
average grower might want to provide, also they will take a long time to reach
maturity. In my experience that hardiness
and vigor of these tiny keiki vary depending on the species. Keiki of anosmum,
cucullatum, crumenatum and primulinum
larger than two inches long, are quite hardy and survive very well if given
appropriate care and an environment with high air humidity. I have not been so lucky with small keikis of
the Phalaenanthe section and of the
“antelope” Dendrobium of the Sphatulata section. In my experience keiki from these groups
take more time to grow larger, produce roots more slowly and succumb to rot
more readily. Admittedly this is
probably due to the particular environment in which I keep the keiki in my
orchid growing area, some people elsewhere might have a different results.
I have observed that older canes
sometimes produce keiki even in the absence of any of the issues that I have
detailed previously. My guess as to what
causes this is that keiki production in older canes is probably related to the
loss of the roots that are connected to that particular cane. In these cases the plant still has a healthy
root system in his younger canes and all the canes receive moisture from those
roots, so this keiki production is not related to any distress from the part of
the plant. I don’t cut out these keikis
until they have at least two canes and a significant number of roots.
If a cane losses its vascular
connection with the rest of the plant it can start producing keiki. This may happen if part of the stem rots or
is damaged. If the base of the stem is
buried in the media the death of the base of the stem might not be evident to
the casual observer. Also even though
the cane connection to the vascular system is severed there still might be a
substantial amount of dead but not decayed tissue holding the cane together
with the rest of the plant. When this
happens to my pendent Dendrobium I
may cut the cane in the part that has decayed and plant the keiki, still with
the cane attached, in another container or mount. This often makes a huge difference in the
speed in which the keiki reaches adults size, as the piece of cane can provide,
if large enough, with enough support to allow the keiki to produce a
substantially larger new cane in its next growth phase.
Many growers propagate their Dendrobium using the capacity of these
plants to produce keiki. They cut the
older canes into three to four node sections and lay them in sand that is kept
moist. I have seen this method producing
satisfactory results with canes from “soft cane” Dendrobiums such as anosmum,
cucullatum and with many of the types of the Dendrobium that are available at department stores and that are
lumped in the literature under the denomination “evergreen”.
