Byblis--Notes on forms new to cultivation
(Carnivorous Plant Newsletter, 1993, 22:2, 39.)
Because of the efforts of our intrepid colleague Allen Lowrie of Western
Australia, there are some new forms of Byblis in cultivation
(B. aff. liniflora "Darwin", "Kununurra", and
"Robust straggling plant, Darwin"---hereafter "Darwin", "Kununurra", and
"Robust", respectively).
During the past few years I have been growing them and
learning about their cultural requirements. Byblis is a genus
of passive flypaper plants similar to Drosera--indeed the
species D. indica looks much like a Byblis.
The major characteristic distinguishing the two genera is in the arrangement
of the floral sexual organs. In Drosera the five stamens are
arranged symmetrically around the ovary and there are five (often branched)
styles also symmetrically arranged. In contrast Byblis flowers
are subtly zygomorphic. The five stamens are
grouped together to the side of the ovary--the five curved anthers
looking like a bunch of bananas--while the single pistil extends
away from the bundle of anthers.
The most
commonly grown plant in the genus is B. liniflora. This is
certainly the easiest plant of these to grow because its seeds germinate and
grow in any medium without any special treatment. I prefer to use a
50/50 sand/peat mix in a deep pot because the plants live longer.
In smaller pots they tend to be annuals.
In big pots they also they branch more to make a bushy plant, especially
if just a few plants are grown in a pot. The first flowers appear when the
plant is just a few months old, and seed is produced generously without
intervention--this plant is a weed!
B. gigantea is more challenging. The seeds must be pretreated
in order to germinate well. I have tried boiling water, bleach,
gibberellic acid,
and patience, but I have found the best way is by fire! The sort of fire
you need to produce is a cool burn. I gather some completely dried grasses
and straw and make a loose pile on the
soil surface of my pots, several centimeters tall and broad. When I light the
fire I puff on it so it burns vigorously for about 20-30 seconds before
burning out.
When I set fires for seed in plastic pots I first bury the pots to the rim in
large buckets filled with moist sand. This prevents the plastic pot from
melting. Because I am a little paranoid about the effects of unknown variables,
I always use dead grass from areas I know haven't been treated with pesticides
or herbicides.
I think it may be important to let the seeds sit on a moist
soil surface for a week or two before they are fire treated.
Germination should follow in a few weeks. While Adrian Slack in foggy England
and other growers in humid environments may need tuning forks to induce the
anthers to release pollen, I have found this is not necessary in my 60%
humidity Arizona greenhouse. Holding the flower petals
with thumb just under the
mature stamens I briskly rub or flick the anthers a dozen or more times. Pollen
collects on the thumb. Tuning forks will also work but are a bother.
"Kununurra" needs no special treatment to germinate, and
is catholic regarding soil mixes.
It is a lanky form with a weak stem and large internode distances.
It grows to a meter or more long,
generally causing problems as it scrambles though the tops of my
Sarracenia. Often the entire plant is pale green. It grows best in
pots 15 cm (6") or more deep. I have grown this giant in
5 cm pots (2") housing four plants, but the plants were dwarfed in all
respects to about one half normal size. These plants also became tinged
with red color overall. "Kununurra" needs a tuning fork or similar
method (such as mine above) to release pollen. Cross pollination
is required for it to set seed. This means you must have two plants
flowering approximately concurrently.
Self a plant all you like, but you will get nothing
for your labours. The flowers on "Kununurra" are very large (2-3 cm across),
nearly as big as on B. gigantea. The petals on the
largest flowers are clearly placed in a zygomorphic arrangement. Two of
the petals are paired on one side of the flower, and the other three are
grouped on the other side of the flower, very much like on most Mexican
Pinguicula. The petals on smaller flowers do not show this
asymmetry.
"Darwin"
must be exposed to fire to germinate well. When I first tried to germinate
this plant I did not use fire and nothing happened. A year later I tried
another batch of seed and got rapid germination after an experimental firing.
Heady with success, I fired the old pot which had been sitting
moist in a tray for a year and got more seedlings! This plant has a
compact bushy habit with many small flowers. The entire plant is deep red.
"Darwin" will self naturally and produce seed. I
made a delightful discovery about "Darwin" when I was collecting seed for the
first time. At the time I was mildly annoyed because
the seed capsules do not split open when they dry out at maturity.
Instead they stay firmly sealed. Since the capsules are sturdily made,
this makes collecting seed a little irritating because each must be forcibly
but carefully smashed without losing seed. But I noticed one of the seed pods
still on the plant
had opened widely without my intervention. Thinking about how
Erodium, Lithops and other plants use moisture as an
aid in seed dispersal, I dunked a sealed "Darwin" seed capsule in water
and was delighted when, a few minutes later, the capsule halves splayed
open like a mussel opening at low tide, revealing the seeds within!
"Darwin" is a wonderful plant to think about--it requires water for seed
dispersal and fire for germination. I wonder if a brush fire swept through
"Darwin" habitat, would seeds locked in dry capsules survive the conflagration
and be liberated when their capsules burn away? Thus heat treated, they
would be ready to germinate. This is similar to a fire survival method some
pines trees have--their tough cones do not release seed until a fire
opens them.
B. liniflora and "Kununurra" both have small seeds and do not
require a fire treatment, while B. gigantea and "Darwin" have large
seeds which must be burnt. My seeds of "Robust" were of intermediate
size but also responded well to fire. My plants are largely indistinguishable
from "Darwin", but other growers tell me their plants look more like
"Kununurra". So I am not too sure of what is happening here--I think
somewhere some seed has gotten mixed up. Capsules of my "Robust" open with
water the same as "Darwin".
Are the forms "Kununurra" and "Darwin"
taxonomically significant, or are their morphological differences
minor or even induced environmentally? Certainly it is not
environmental, because all my plants are growing in the
same conditions, in partial shade in trays (I know my descriptions
of the plants sound like I'm
growing "Darwin" in full sun and "Kununurra" in a dimly lit closet!).
I have experimented with hybridization to see if I could make
crosses between these forms. Since "Kununurra" does not produce seed if
selfed, it makes an ideal maternal parent since it eliminates the danger
of accidental selfings. I pollinated "Kununurra" flowers with pollen
from "Darwin" and waited. Within a few days I could tell the crosses
were not being successful, because "Kununurra"
flowers which are successfully pollinated usually lose their petals within
two days. Repeated attempts at making this cross have produced no seed.
Since the flower parts are so large I am sure I am successfully making
the cross, especially since my crosses between different clones of
"Kununurra" invariably produces seed. I think I am encountering a genetic
barrier--in other words, "Kununurra" and "Darwin" are certainly different
species and should be formally described. All these plants are interesting
and easy to grow. I keep mine sitting in water and away from frost and
they flower and set seed well.
Postscript: After publication of this article, Lowrie & Conran (1998) established the names
B. aquatica for B. aff. liniflora "Darwin"
and B. filifolia for B. aff. liniflora "Kununurra".
I am not sure if the "Robust" plant is the same as one of the other newer Byblis species.