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Calyx Horticultural Services presents

Into Horticulture

Issue 8   June 2012

Plant & Garden News

Myrtle rust reaches FNQ
Myrtle rust has been identified in a number of locations in Far North Queensland including national parks: Myrtle rust spreads to Wet Tropics.

627 years and counting for olive tree
Scientific analysis of "millennium-old" olive trees in northeast Spain has shown the oldest to be 627 years old, one of the oldest recorded in Europe. Small cylindrical samples that allowed counting of the tree rings were taken from the trunks. Previously cut sections of trunk were also examined. The Regional Government of Catalonia now calls these famous olives "monumental trees" instead of "millennium-old". Source: The millennium-old olive trees of the Iberian Peninsula are younger than expected.

Another type of insect-dependency by carnivorous plant
A symbiotic relationship between a carnivorous plant an insect has been discovered on Borneo. Ants living with Nepenthes bicalcarata appear to help the plant by assisting with the capturing and digestion of prey, with nutrients being passed on to the plants in the ants' wastes. The pitchers alone are inefficient and without ants the plants become nutrient stressed. In turn, the plant provides a specialised structure (domatia) for the ants to live in, and nectar for them to eat in addition to the insect prey they help catch. Original paper here: A Carnivorous Plant Fed by Its Ant Symbiont: A Unique Multi-Faceted Nutritional Mutualism.

Bowerbirds are gardeners, too
Research carried out in Taunton National Park in Queensland has revealed a high number of Solanum ellipticum around bowerbird bowers. Seeds in the fruits used to decorate them appear to be germinating nearby after the fruits are discarded, assisted by the birds' prior clearing of grass and weeds from the area. The scientists believe this is first known example of a species, other than humans, cultivating non-food plants. The birds also seem to be selecting for plants with more ornamental properties, with plants near bowers bearing fruit of a preferred greener colour. Source: Birds cultivate decorative plants to attract mates.

UK garden market not recession-proof
Analysis released by the UK's Horticultural Trades Association in April 2012 has shown economic conditions are affecting consumers' garden spending. Most impacted were sales of items like garden furniture or tools, which could be delayed or the best deal found online. In contrast, plant sales only fell slightly. The HTA stresses the importance of sustaining the interest of younger consumers through this time, as they will be the industry's customer base in future. read more at the HTA website: Opportunities for garden retail growth in spite of the pinch.

The biggest plant catalog of them all
Four of the world's great botanical gardens are to collaborate on a World Flora, involving a compilation of information on some 400,000 species into an online catalog. It will be built on The Plant List, a database of accepted names and synonyms of all known plant species. The World Flora will include descriptions, images and distribution information and has a projected completion date of 2020. Source: Four prominent botanical institutions announce plans to create first online World Flora.

Plant responses to touch investigated
Researchers at Rice University, Texas, have demonstrated that touching plants can stimulate the plant hormone jasmonate, which stimulates chemical defences against insects and fungi. The tendency for plants to grow shorter and slower when touched has also been linked to this plant hormone. In nature, wind or insects and other animals could induce these responses. Source: A bit touchy: Plants' insect defenses activated by touch.

Conifer an alternative to whale-scented fragrances
In spite of it's inelegant origins, ambergris is highly valued as a fixative in perfumes. However, the fragrance industry may soon have access to a plant-based alternative, thanks to the efforts of Canadian researchers. They've found a gene in the balsam fir tree (Abies balsamea), which could be used to produce a comparable substance more cheaply more reliably. Source: How to make high-end perfumes without whale barf.

Plant chatter
Research at the The University of Western Australia could be early evidence that plants can respond to sound, and may even use it to communicate with each other. Young roots of corn were found to emit a clicking sound in the 220Hz region. Furthermore, roots suspended in water were shown to lean toward a continuous sound source of similar frequency. It is possible that sound and vibration play a previously unrecognised role in plant function. Source: Talking plants.

Biochemical memory helps plants respond to future drought
Scientists have confirmed that "training" plants to tolerate periods of water stress can indeed help them cope better next time. Via changes in chromatin, the plants appear to "remember" prior stress and respond to subsequent dehydration by increasing transcription of certain genes. The findings could be used in future engineering of drought-tolerant crops, but can be applied to current plant management techniques. For example, by "hardening" off seedlings prior to transplanting by deliberate withholding of water. Source: UNL Scientists Find Plants 'Remember' Drought, Change Responses to Survive.

The secret of van Gogh's sunflowers
The sunflowers painted by van Gogh have a proliferation of yellow petals and a reduced central disc compared to common sunflowers which typically have a only single whorl of yellow "ray florets". A mutant gene creating a double-flowered inflorescence has been identified. A double varieties screened have the same mutation, suggesting this is the indeed the one responsible for the blooms van Gogh painted. Similar varieties are popular today as ornamentals and cut flowers. UGA scientists reveal genetic mutation depicted in van Gogh's sunflower paintings.

Editorial

Hooray for Trey

With a fairly lengthy article about mussaendas this edition, just a quick recommendation here for anyone working in the nursery industry in Australia. If you haven't discovered him already, check out Trey Pitsenberger, The Blogging Nurseryman

An independant garden centre operator in California, Trey blogs about his experiences and insights in coping with "Big Box" competition, worsening economic conditions and changing social trends. The focus is on taking control and taking action. Trey's blog and industry Facebook groups are an example of that.

Pay Trey a visit today: The Blogging Nurseryman by Trey Pitsenberger
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 illustration
illustration
Top: Enlarged sepals are the showy part of the Mussaenda inflorescence. Below: Enlarged portion of top photo showing partly-opened petals of one flower

Feature Plant

The Mussaendas

The mussaendas are a group of highly ornamental shrubs suited to tropical and subtropical climates with a bright future, both as landscape plants and as potted floral decorations.

They're members of the large Rubiaceae family, which also contains Gardenia, Ixora, Pentas and Coffea (coffee).

The most distinctive feature of Mussaenda (and some other genera of the Rubiaceae) is that the floral display is primarily derived from the calyx, with some individual flowers within an inflorescence carrying an enlarged petaloid sepal. Some cultivars have all five sepals enlarged. These are called calycophylls or sometimes semaphylls (that is, a structure which signals a pollinator). In many publications, these are erroneously referred to as bracts.

There are Mussaenda species native to Africa, Madagascar, Asia and the Pacific. Commonly cultivated species include Mussaenda philippica, M. erythrophylla, M. frondosa and Pseudomussaenda flava (also referred to as Mussaenda flava, M. glabra, M. luteola, M. lutea or M. incana in various publications).

University of the Philippines Los Baños has been active over many decades in breeding these ornamentals and is responsible for the popular cultivars 'Queen Sirikit', 'Doña Aurora' and 'Doña Luz'. Many more cultivars have been developed in the Phillipines, although not widely available in Australia.

Many are named after First Ladies and other notable women of the Phillipines, hence the Spanish form of address "Doña" in some cultivar names. 'Queen Skirit' was named after the Queen of Thailand to commemorate a visit to the Phillipines.

Mussaenda can produce seed (in a small fruit), but production is poor and unreliable. Seed is significant for the purposes of hybridising but vegetative methods are used for commercial propagation.

Cuttings can be also be difficult to strike, although this varies among cultivars. Alternative means of propagation include grafting, layering and marcotting. Refinement of methods for mass propagation of the more difficult cultivars (cutting type, growth regulators, incubation conditions, etc) could mean a greater range of cultivars available for purchase in the future.

These soft-wooded shrubs can have some tendency to climb, so depending on pruning they can be kept as shrubs, trained as small tree or allowed to scramble through a nearby tree. They are suitable for full sun or part shade.

The major attractions of mussaendas in the landscape is their extended flowering period. They will loose their leaves and go dormant through the cooler and drier winter, but put on a spectacular display throughout the warm, wet months. If conditions are suitable, they can flower year-round. They have poor drought and cold tolerance.

 illustration illustration
'Capricorn Ice' PBR and 'Capricorn Dream' PBR are two Mussaenda cultivars developed by Orams Nurseries in Queensland, Australia

Some species and cultivars have proven to be better performers than others outside of the tropics and local breeding efforts may help improve the popularity of mussaendas in subtopical and warm temperate parts of Australia. Orams Nursery, near Rockhampton on the central Queensland coast, have released two cultivars 'Capricorn Ice' PBR and 'Capricorn Dream' PBR.

In addition to their role in the garden, mussaendas have potential as potted floral gifts. Research in the Phillpines investigating appropriate treatment including growth regulators and selection of suitable hybrids is aimed at developing this market. Given that Mussaendas can bloom year-round in suitable climates, there is presumably no daylength requirement. This gives them a particular advantage over Poinsettia as a floral Christmas decoration in parts of the world where flowering must be artificially induced.

As research and hybridisation work progresses, cultivars with new colours, growth habits, climatic tolerances and amenability to propagation could mean that we'll be seeing more of these these flamboyant shrubs in our lives in the future.

Bibliography and Further Reading:
An extensive list of links to more information about Mussaenda, including publications used in preparation of the article above is based, can be found at www.calyx.com.au/mussaenda.html.

Acknowledgment: Thanks to Orams Nurseries for additional information and images of their cultivars.

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Into Horticulture (http://www.queenslandgardening.com/newsletters.html) is a free newsletter aimed at professionals in the nursery & garden industry, plus expert amateur gardeners. There's an emphasis on issues affecting Queensland, but anyone involved in horticulture will find this newsletter interesting and informative.

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