Barry Rice
- doing science on a terrestrial planet -
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 WesternAustralia, there are some new forms ofByblis 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 andlearning about their cultural requirements.Byblis is a genusof passive flypaper plants similar toDrosera--indeed the speciesD. indica looks much like aByblis.The major characteristic distinguishing the two genera is in the arrangementof the floral sexual organs. InDrosera the five stamens arearranged symmetrically around the ovary and there are five (often branched)styles also symmetrically arranged. In contrastByblis flowersare subtly zygomorphic. The five stamens aregrouped together to the side of the ovary--the five curved antherslooking like a bunch of bananas--while the single pistil extendsaway from the bundle of anthers.
The mostcommonly grown plant in the genus isB. liniflora. This is certainly the easiest plant of these to grow because its seeds germinate andgrow in any medium without any special treatment. I prefer to use a50/50 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, especiallyif 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 pretreatedin 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 fireyou need to produce is a cool burn. I gather some completely dried grasses and straw and make a loose pile on thesoil surface of my pots, several centimeters tall and broad. When I light thefire 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 inlarge 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 pesticidesor herbicides.I think it may be important to let the seeds sit on a moistsoil surface for a week or two before they are fire treated.Germination should follow in a few weeks. While Adrian Slack in foggy Englandand 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 petalswith thumb just under themature 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, andis 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 mySarracenia. Often the entire plant is pale green. It grows best inpots 15 cm (6") or more deep. I have grown this giant in5 cm pots (2") housing four plants, but the plants were dwarfed in allrespects to about one half normal size. These plants also became tinged with red color overall. "Kununurra" needs a tuning fork or similarmethod (such as mine above) to release pollen. Cross pollinationis required for it to set seed. This means you must have two plantsflowering approximately concurrently. Self a plant all you like, but you will get nothingfor 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 ofthe petals are paired on one side of the flower, and the other three aregrouped on the other side of the flower, very much like on most MexicanPinguicula. The petals on smaller flowers do not show thisasymmetry.
"Darwin" must be exposed to fire to germinate well. When I first tried to germinatethis plant I did not use fire and nothing happened. A year later I triedanother 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. Imade a delightful discovery about "Darwin" when I was collecting seed for thefirst time. At the time I was mildly annoyed becausethe 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 forciblybut carefully smashed without losing seed. But I noticed one of the seed podsstill on the planthad opened widely without my intervention. Thinking about howErodium,Lithops and other plants use moisture as an aid in seed dispersal, I dunked a sealed "Darwin" seed capsule in waterand was delighted when, a few minutes later, the capsule halves splayedopen like a mussel opening at low tide, revealing the seeds within!"Darwin" is a wonderful plant to think about--it requires water for seeddispersal and fire for germination. I wonder if a brush fire swept through"Darwin" habitat, would seeds locked in dry capsules survive the conflagrationand be liberated when their capsules burn away? Thus heat treated, theywould be ready to germinate. This is similar to a fire survival method somepines trees have--their tough cones do not release seed until a fireopens them.
B. liniflora and "Kununurra" both have small seeds and do notrequire a fire treatment, while B. gigantea and "Darwin" have largeseeds which must be burnt. My seeds of "Robust" were of intermediatesize but also responded well to fire. My plants are largely indistinguishablefrom "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 differencesminor or even induced environmentally? Certainly it is notenvironmental, because all my plants are growing in thesame 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 makecrosses between these forms. Since "Kununurra" does not produce seed if selfed, it makes an ideal maternal parent since it eliminates the dangerof 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 withintwo 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 geneticbarrier--in other words, "Kununurra" and "Darwin" are certainly differentspecies and should be formally described. All these plants are interestingand easy to grow. I keep mine sitting in water and away from frost andthey flower and set seed well.
Postscript: After publication of this article, Lowrie & Conran (1998) established the names B. aquatica forB. aff. liniflora "Darwin"and B. filifolia forB. aff. liniflora "Kununurra".I am not sure if the "Robust" plant is the same as one of the other newer Byblis species.