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Calyx Horticultural Services presents

Into Horticulture

Issue 16   August 2014

Plant & Garden News

For healthier people, plant trees

A US study has estimated that trees save the lives of more than 850 Americans and prevent some 670,000 acute respiratory incidences per year by removing air pollution. These positive health effects were valued at nearly $7 billion annually. Source: First national study finds trees saving lives, reducing respiratory problems: Air pollution modeling reveals broad-scale impacts of pollution removal by trees

Sound as pest control

Test plants exposed to recordings of feeding vibrations later showed greater production of mustard oils when fed on by actual caterpillars. Other types of vibrations did not increase these chemical defences. Besides revealing new ways that plants interact with their environment, the research points to ways that natural defences might be stimulated by growers. Source: Plants Respond to Leaf Vibrations Caused by Insects' Chewing, MU Study Finds

Axinaea stamens an unusual bird treat

An unusual form of bird pollination has been described in the genus Axinaea from Central and South America. Instead of the more usual nectar, the stamens carry bulbous appendages which provide birds with a food reward. However, the structures incorporate a "bellows" action which eject pollen on to the bird in the process. Most of Axinaea's relatives in the family Melastomataceae are pollinated by bees. The researchers speculate that the strategy adopted by Axinaea may be an adaptation to growth at high altitudes , where bird pollination may be more efficient. Source: Flower's bellows organ blasts pollen at bird pollinators

Some roses tested for salt tolerance

18 popular rose cultivars promoted by Texas A&M University under the Earth-Kind® brand for their pest tolerance and landscape performance have also been tested for salt tolerance. The cultivars varied, with 'Sea Foam' being one of the best and 'Cecile Brunner' one of the worst. Source: Earth-Kind roses analyzed for salt tolerance.

Acacia seeds tough it out

Two wattles planted at the Royal Botanic Garden Sydney represent the durability and future potential of the genus for deployment in extreme conditions. One (Acacia pycnantha), was grown from seed that survived the microgravity and ionising radiation of 2800 Earth orbits in space, the other (Acacia obtusata) was grown from seed stored since 1899. Source: Wattles - to infinity and beyond

New hope for late blight resistance

The centre of origin of potato late blight, Phytophthora infestans has been genetically tracked to a valley in central Mexico. The cause of the devastating Irish Potato Famine and a serious and costly crop disease worldwide today co-evolved with relatives of the potato in this valley, from where it spread repeatedly. The discovery presents tremendous opportunities for finding resistance genes. Source: Tracking potato famine pathogen to its home may aid $6 billion global fight

Ornithophily at least 47 million years old

The oldest known example of ornithophily (the pollination of flowers by birds) has been recently described. Even though structural features of bird fossils had previously suggested a such relationship, pollen found in the stomach contents of a bird from the Messel Pit (Germany) has confirmed that it goes back at least 47 million years. So far, there are no plant fossils of this age suggesting ornithophily, but typical indicators like red flowers of lack of scent are not preserved by fossilisation. Source: Age-old: Relationship between Birds and Flowers- The world's oldest fossil of a nectarivorous bird has been described

Antioxidant roses
Rosa canina
Rosa canina. Photo by Valentina Schmitzer

A Slovenian study in which several rose species and modern cultivars were compared, showed differences in levels of phenolic compounds, Among those tested, Rosa canina leaves exhibited high and varied content of the antioxidants. This could be an underlying reason for the popularity of this species in traditional medicine. On the other hand, the modern cultivar 'Schwanensee' had the lowest levels of those tested, which might explain its susceptibility to disease. Differences in phenolic makeup of indigenous rose species and modern cultivars

New nickel collector

A new plant species has been discovered in the Philipines that can accumulate nickel in its tissues at levels up to 1000 times higher than other plants, without being poisoned. Only about 450 species worldwide have exhibited nickel hyperaccumulation, a property which could be used for phytoremediation of contaminated soils, or even phytomining. Source: New species of metal-eating plant discovered in the Philippines

Temperature effects on plants can be complicated

In cold climates, warm temperatures might be assumed to increase growth. However, a study on two shrub species on an island south of New Zealand showed that episodes of activating warmth during winter are actually detrimental. Elevated respiration, especially by the roots, depletes plant reserves. If this were to occur repeatedly over many years, it could affect on the survival of these species. This indicates one of the unexpected consequences that a warming climate could have on plant life. Shrub growth decreases as winter temps warm up


Exposed complex mixture of plant aromas in a greenhouse of tomato plants, confused whitefly had trouble feeding in a UK study. The effect was temporary (no more than 15 hours), but could point to ways to delay attack until plant defenses can be activated. Source: Whitefly confused by cacophony of smells

Plants in glass houuses

Glass formed naturally in the extreme heat of a comet or asteroid impact in what is now Argentina has been found to contain plant matter. This has preserved detail down to the micron level, Scientists think that looking at impact glass on Mars could pould potentially reveal signs of former life if it existed there. Source: Impact glass stores biodata for millions of years


Remember Cut Flowers?

Back in the day, home-grown flowers were a simple and inexpensive pleasure. They could adorn a home or serve as a gift for guests to take home with them as a reminder of their visit (and of the gardening skills of the hosts).

While the production of more elaborate and artistic creations were considered a suitable hobby for ladies of adequate means and leisure, flowers were more often humbly arranged in a vase, or even just a jam jar.

In more recent years, however, it seems that people simply don't think so much about picking and using flowers indoors. The reasons would seem to be fairly obvious - less access to flowers due to shrinking yards and shrinking time in which to garden. Also, water shortages and general fashion trends have seem a trend towards fewer flowers and more minimalist and "architectural" plants like succulents and grasses.

Lately there has been a new wave of interest in "grow your own" but that's mostly about edibles. Some people are even digging up their front gardens to grow more vegetables. Wasting space on flowers is not on. Some would even consider it irresponsible.

Given the resurgence of interest not only in vegetable growing but in cooking, the handmade and locally made, green living and retro everything, perhaps flowers for the house could also see a revival. Especially with support from the horticultural industries.

In the next edition of this newsletter, why and how the industry might be more involved will be discussed. Meanwhile, presented below is part one of an article about a popular type of plant that many Australians would have growing in their gardens but probably never thought about using indoors - grevilleas.

Have a rummage around in the back of the cupboard and dust off those vases!

New plants or products

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Feature Article

Grevilleas as Cut Flowers - Part One

The woody plant genus Grevillea contains some of the showiest members of the Australian flora and are among the most popular natives for garden cultivation in this Australia. In addition to the species, hybridisation and selection has produced many cultivars in a wide variety of floral colours and forms which are appreciated by both humans and birdlife. Furthermore, the range of growth habits from trees and shrubs to prostrate groundcovers mean they can be utilised in many ways in the landscape.

While a familiar sight in local gardens, grevilleas aren't generally thought of as flowers for cutting. This is in spite of the fact that many of their cousins in the family Proteaceae Banksia and Telopea (better known as Waratah) and the African genera Protea, Serruria, Leucadendron and Leucospermum are well established in the commercial trade [1,2]. Nevertheless, in recent years there has been increasing interest in Grevillea by the industry at home and abroad.


Before discussing use of the actual flowers, the value of grevillea foliage in floral arrangements must be acknowledged. Many Grevillea species have interesting leaves which are variously shaped and coloured and some of the early interest by florists actually lay with the foliage rather than the flowers. An American floriculture manual published in 1922 refers to using seedlings of Grevillea robusta (Silky Oak) to fill out window boxes as a substitute for Boston fern [3].

More recently Grevillea baileyana has gained attention for its lobed juvenile leaves with bronze undersides and their long vase life [4].


While individual flowers (florets) all display the distinctive Proteaceae morphology [5], the number and presentation in the inflorescence varies considerably. For floristry, varieties with large cylindrical/conical brush-type blooms borne at the ends of branches have received the most attention. Most have parentage including Grevillea banksii or related species [6] derived from subtropical and tropical parts of the continent.

Short vase life has been a major impediment to the use of grevilleas as cut flowers in the past, with premature abscission of the florets from the stalk being a common complaint. Wilting and colour loss can also be a problem. Work is being done, however, to improve the ability of the flowers to withstand transport and handling and give the final recipient a satisfactory display.

One of the most important discoveries has been determining the best stage at which to harvest. The point at which styles fully emerge from the flowers is too late. The blooms should be picked while the styles are still looped within the perianth. This may be between 10% to 100% of styles on the inflorescence looped, with the optimum depending on the cultivar [7,8].

Other lines of research include treatment with sugars, hormones or other chemicals after harvest or in the vase water. Such techniques are used with many other floral crops. It is also important to know factors such as ethylene sensitivity and optimal temperature and humidity [9].

Furthermore, some varieties have been shown to perform better than others, which suggests hybridisation and selection could produce even better varieties. Some work in this direction has been done [6,10].

Next time in part 2 - Using grevilleas from your garden

References and other sources

[1] Commercial Growing of Cut Flowers Australian Native Plants Society (Australia)
[2] Proteaceae Floral Crops: Cultivar Development and Underexploited Uses Perspectives on new crops and new uses, ASHS Press
[3] Fritz Bahr's commercial floriculture; a practical manual for the retail grower
[4] Spectacular Foliage from the Tropical North Australian Native Plants Society (Australia)
[5] Grevillea-Background Australian Native Plants Society (Australia)
[6] Grevillea : Breeding and Development of Cut Flowers Rural Industries Research and Development Corporation
[7] Quality specifications for Australian wildflowers. Cultivar: 'Moonlight' Rural Industries Research and Development Corporation
[8] Tropical grevilleas vase life better than expected. Australian Horticulture, Sept 1996 p43-45
[9] Postharvest Handling of Australian Flowers from Australian Native Plants and Related Species Rural Industries Research and Development Corporation
[10] Vase life characteristics of selected Grevillea (Abstract) Australian Journal of Experimental Agriculture, CSIRO Publishing
Development and senescence of Grevillea 'Sylvia' inflorescences, flowers and flower parts. University of Queensland
Stem end blockage in cut Grevillea 'Crimson Yul-lo' inflorescences University of Queensland

For more background information about grevilleas in general see the list of links on

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