No. 10 Darwinia, Chamelaucium and Verticordia IN THIS ISSUE Darwinia, Chamelaucium, This issue of Seed Notes will cover the genus and Verticordia Darwinia, Chamelaucium and Verticordia. The three genera, DChamelaucium, Darwinia and D Description Verticordia form part of the D Geographic tribe Chamelaucieae belonging distribution and to the Chamelaucium alliance habitat of the family Myrtaceae. D Reproductive biology They share many distinctive characteristics and will be D Seed collection treated in this publication as a D Seed quality group. The genus Darwinia was assessment named after Dr Erasmus Darwin, Above: Verticordia aurea. Below: Verticordia fragrans. Photos – Anne Cochrane the grandfather of the naturalist D Seed germination Charles Darwin. The meaning of Description D Recommended reading the name Chamelaucium is not very clear, although in Greek, DAll three genera consist of chamai means dwarf or on the woody perennials. They ground and leucos means white. range from dwarf shrubs Verticordia was named after the suitable as groundcovers, Roman goddess Venus due to to medium shrubs reaching the beauty of the flowers. several metres in height. Their leaves, which are more D often than not opposite, small and narrowly linear, all exhibit the distinctive aromatic smell of the family Myrtaceae. Many species within the Chamelaucium alliance have attractive, long lasting ornamental flowers, in particular the bells of the Darwinia and the small waxy flowers of the Chamelaucium. Many species have great potential occur in a range of colours for ornamental horticulture, from white to pink and to presenting an important red. Verticordia flowers future for floriculture (e.g. are feathery and often Chamelaucium uncinatum). prominently displayed, Flowers of the genus borne singly but appearing Darwinia come in green, as heads or spikes. They are yellow, pink and red while generally brightly coloured, those of the Chamelaucium ranging from yellow to red and to purple. Inter-generic Above right: Verticordia albida. hybridisation may occur Left: Verticordia penicillaris. between different species Photos – Anne Cochrane within the genera.D Seed Notes 10 page 1 Geographic distribution and habitat Seed collection These three genera are Species in the Chamelaucium alliance have indehiscent fruits, Dendemic to Australia, with a or nuts, that usually contain only one seed and are shed large proportion of species annually. They are never discharged but the entire flower of Darwinia and Verticordia dries and breaks off below the receptacle. Seed must be found in south-western collected when mature and timing of collections is important. Australia. Chamelaucium is It is possible to collect seed of each of the three genera entirely endemic to Western from below plants but insect predation may be higher in Australia. There are more such collections. Old flowers of Verticordia form the fruit than 150 species in the genus and hence old faded flowers are collected when they easily Verticordia; more than 20 in come off the plant. Both Darwinia and Chamelaucium form Chamelaucium and more than Approximate distribution of Darwinia, Chamelaucium and fruits that appear different from the flowers and turn brown 60 in Darwinia. All these plant Verticordia in Australia. and leathery to hard when ripe. For most species in the genera occupy a prominent place three genera several months from the beginning of flower in many shrub and heathland initiation to seed collection are needed. Most Darwinia and communities together with other myrtaceous genera such Chamelaucium are spring flowering with summer fruiting, as Callistemon, Agonis, Leptospermum, Melaleuca and whereas Verticordia may be either spring or summer flowering Calothamnus. Most species appear to have a need for well- and seed is ripe for collecting mid summer. drained soils, although many grow in a wide range of soils and D climatic conditions. Darwinia are found in sandy coastal heaths and in the species rich mountains of the Stirling Range National Park. Verticordia and Chamelaucium can be found on laterite, granites and in deep siliceous sand. Many populations of these genera are at risk of local extinction in the near future due to a range of threatening processes. These include disease, weed invasion, salinity, small population sizes, habitat fragmentation and/or continued land clearing. Over-picking of flowers from the wild also has impacted wild populations of several species, common and rare. In addition, Darwinia are considered susceptible to the dieback disease, Phytophthora cinnamomiD. Above: Collecting seed of the rare Verticordia staminosa ssp. cylindracea var. erecta. Photo – Anne Cochrane Reproductive biology Most species in the Chamelaucium alliance are likely to be Dpollinated by either specialised or unspecialised insects, and may include native bees and wasps. Darwinia species that have a conflorescence surrounded by bracts may possibly be bird- pollinated whereas most other members of the genus are thought to be insect-pollinated. It has been postulated that Verticordia grandis may be bird Above: Darwinia citriodora. pollinated due to the flower Photo – Andrew Crawford structure. Apparent pollinator mutualisms also have been reported for some other species of Verticordia. Profuse flowering in some species indicates intense competition for pollinators. Honey eating birds are frequent visitors to the flowers of Single flower of Verticordia all three genera. carinata. D Photo – Anne Cochrane Seed Notes 10 page 2 Seed quality assessment Seed germination It is very difficult to determine from a cursory visual assessment Dwhether or not a seed has formed within the fruits of Darwinia, Chamelaucium or Verticordia. Seed set is often low, particularly in Verticordia. To determine whether seed has set, it is necessary Verticordia fimbrilepis. to perform a cut test on a representative sample of fruit. Simply dissect the fruit with a scalpel blade. If you wish to keep the seed for germinating then care is needed not to damage any Chamelaucium griffinii. seed found. It is preferable to use a microscope for this job. Seed needs to be white, firm Species in all three genera are and translucent for it to considered difficult to grow from Dseed. Plants have traditionally be considered healthy and potentially viable. been propagated by cuttings. In Darwinia and Chamelaucium, It is likely that seed dormancy it is far easier to determine in Verticordia, Darwinia and Darwinia collina seed dissected from fruit is influenced by whether seed has formed (above) and whole fruit (below). Chamelaucium within the fruit. The fruit Photo – Anne Cochrane a complex interaction of factors. will be slightly swollen at the The breakdown of seed dormancy base and in the case of the and the transition of dormant latter, it may be glossy seed to germinable seed appears and not shrivelled. to require not only the removal D of the seed coat, which acts as Verticordia staminosa a barrier to water uptake, but ssp. cylindracea. also the addition of growth hormones to overcome an Whole fruits of Chamelaucium after-ripening requirement. aorocladus; central right fruit coloured It is possible that the and plump indicating good seed. hypanthium (floral tube) Darwinia chapmaniana seed and perianth (sepals and and fruit. petals of a flower) might help protect the seed from weathering, thus Chamelaucium uncinatum. maintaining dormancy. Dormancy breaks down naturally over time because of weathering and soil Chamelaucium aorocladus disturbance. Many species in seed and fruit. these three genera appear to have a strong reliance on Darwinia leiostyla seed fire to stimulate germination, and fruit. indicating heat and/or smoke Verticordia spicata may help alleviate dormancy ssp. squamosa. in seeds. Recent research has demonstrated smoke responsiveness for some Verticordia albida species. Naked seed from the Germinating seeds of partially dissected cut test mentioned under Seed Chamelaucium, Darwinia and flower revealing seed. Quality Assessment can be grown Verticordia. in the jelly-like substance agar, or Photos – Anne Cochrane put into small dishes with filter Darwinia acerosa. Fruit on right paper and kept moist. Some seed swollen and holding seed; fruit on will germinate after several weeks. left shrivelled with aborted seed. If access to the growth hormone gibberellic acid is available then additions of this to the agar or Darwinia oxylepis seed and fruit. filter paper at 25 mg per litre will Photos – Anne Cochrane greatly assist germination. D Seed Notes 10 page 3 Seed Notes for Western Australia These Seed Notes aim to provide information on seed identification, collection, biology and germination for a wide range of seed types for Western Australian native species. They have been written and compiled by Anne Cochrane, Manager of DEC's Threatened Flora Seed Centre. Concept by Grazyna Paczkowska. Designed by DEC’s Graphic Design Section. The Seed Notes are available from www.naturebase.net Top left: Chamelaucium sp. Gingin. Top right: Verticordia aurea. Above: Verticordia endlicheriana var. angustifolia. Photos – Anne Cochrane Recommended reading Seed Notes Blake, T. L. 1981. A Guide to Darwinia and Elliot, W. R. and Jones, D. L. 1984. are published by Homoranthus. Society for Growing Australian Encyclopaedia of Australian Plants Suitable the Perth Branch of the Plants, Melbourne. for Cultivation. Volume 3. Lothian Publishing, Wildflower Society of Melbourne. Western Australia (Inc.) DCochrane, A., Brown, K., Cunneen, S. and with assistance from Kelly, A. 2001. Intra- and inter-specific Sharr, F. A. 1978. Western Australian Plant the Western Australian variation in seed production and germination Names and their Meanings. A Glossary. Lotteries Commission in 22 rare and threatened Western Australian University of Western Australia Press, Perth. and the Department taxa in the genus Verticordia (Myrtaceae). of Environment and Journal of the Royal Society of Western Conservation (DEC). Australia 84, 3. D 2007501-0308-1 Seed Notes 10 page 4.