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Calyx Horticultural Services presents

Into Horticulture

Issue 13   June 2013

Plant & Garden News

Soil contamination risks in urban gardens

One of the risks of vegetable gardening in urban areas is soil contaminated by toxins. Soil tests may indicate problems, but researchers in Detroit evaluating sampling strategies in a garden plot found that some of the methods failed to detect a lead "hotspot". They suggest that standard sampling procedures be reassessed, and that if possible garden planners check historical records to ascertain what activities the land was previously used for. Source: Detecting Lead Hotspots in Urban Gardens Requires Different Sampling Strategies according to Wayne State research

Tree's mega genome revealed

Sequencing of the largest genome so far completed - seven times the size of the human genome - has been recently been completed and it belongs to a plant. The Norway spruce's huge genome is due to extensive DNA repetition, which is common in conifers. The Norway spruce genome sequenced

Attracting predators with Alyssum

A Washington State University study in which sweet alyssum was grown near apple trees has shown a reduced incidence of wooly apple aphid due to the enhanced predator populations. Six different flowers including marigolds and zinnia were considered for the study, but alyssum was chosen because it attracted the most syrphids (hoverflies), the larvae of which feed on aphids. However, during the study few hoverfly larvae were found. rather, a diverse array of spiders and predactory insects appeared responsible for most of the aphid decline. Protein markers sprayed on the flowers and later identified on predators indicated they had indeed visited the flowers and so were presumably attracted by them. Source: Flower power fights orchard pests

Better germination may be a matter of "the vibe"

Research out of the University of Western Australia suggests communication between germinating seeds of the same or different species can affect growth. Chilli seed germination was helped by the presence of other chillis or basil plants, but hindered by fennel. Plastic barriers blocking chemical transfer suggests "nanomechanical vibrations" may be the mode of comminication. Source: Plants 'talk' to plants to help them grow

Europe to move on neonicotinoid ban

The European Commission looks set to proceeed with a controversial proposal to severely restrict the use of three neonicotinoid pesticides, on the basis of a threat to bees. Included in the group is imidacloprid, formulations of which are popular with home gardeners in Australia. According to the European proposal, home gardeners will not be able to use the chemicals at all. The proposal will be reviewed within two years. More information:
Bees & Pesticides: Commission to proceed with plan to better protect bees European Commssion media release
Bee deaths: EU to ban neonicotinoid pesticides BBC
Bees and the European neonicotinoids pesticide ban: Q&A The Guardian, UK

The Australian Pesticides and Veterinary Medicines Authority (APVMA) has responded with an updated (May 2013) outline of their review of these chemicals currently underway. Read it here: Neonicotinoids and honey bee health in Australia. A draft report for consultation is "mid-2013". (For more on the European ban, see news item below.)

Heat-inhibition of lettuce seed explored

Researchers have discovered a gene responsible for stopping lettuce germination in hot weather. When the seeds are exposed to moisture at warm temperatures, the gene switches on and increases production of absicic acid. This plant hormone inhibits germination. The mechanism may have helped the lettuce's Mediterranean ancestors avoid germinating in the summer, when conditions are usually too hot and dry to allow completion of the life cycle. Identification of the gene may lead to new varieties that don't require seed priming and other expensive and unreliable techiques to achieve year-round crop production. Source: Gene discovery may yield lettuce that will sprout in hot weather

Plant to reduce crime

Contary to the notion that vegetation may encourge crime by providing cover for perpetrators, a study in Philadelphia has shown that even after accounting for factors such as poverty and education levels, areas of the city with grass, shrubs and trees were associated with lower crime, especially robberies and assaults. The authors suggest greenery might encourage a greater degree on community interaction and supervision as well as having a calming effect. Source: Urban vegetation deters crime in Philadelphia

Better concrete from unexpected source
High-lignin cellulosic residues left by some types of biofuel production could be used in concrete manufacture. Replacing some of the cement in the mix with ash of the burnt biofuel byproduct actually increased the strength of the finished concrete. Source: Researchers building stronger, greener concrete with biofuel byproducts
Caffeine helps bees study

Honeybees fed with a sugar solution containing caffeine were better at remembering a floral scent than bees fed sugar only. Caffeine is found naturally in the nectar of coffee and citrus blossoms. This could encourage bees to keep coming back. Bees get a buzz from caffeine

Potato days

Originating near the Equator of South America, wild potatoes were adapted to a regime of shorter days than experienced during the European spring/summer growing season. Mutations in a single gene regulating tuber formation, recent research reveals, allowed the selection of varieties that produced under longer days and led to the potato's importance as a food crop today. in the future, the discovery may facilitate breeding of new varieties suited to specific locations. Source: Discovery of genetic mechanism allowing potato cultivation in northern latitudes

Gardening to be taught in UK schools

As part of a reform of their National Curriculum, gardening will be taught in UK schools from September 2014. Campaigning and research on the benefits of school gardening by the Royal Horticultural Society helped acheive this reform and the organisation will continue to be involved in providing advice and training. Source: RHS Backs Plan for Gardening in Schools

Daffodil flower secret uncovered

The trumpet-like corona is a distinctive feature of the daffodil. Previously thought to be an extension of the petals, new research suggests that it is a distinct organ developing from the hypanthium (the structure on which the floral parts are located) after the petals and stamens are established. Source: How the daffodil got its trumpet


Australian gardeners have been making international news, which is something you can't say every day. Congratulations to Fleming's Nurseries of Victoria for taking out "Best in Show" with their Trailfinders Australian Garden at the 2013 Chelsea Flower Show in the UK. The win, however, has attracted some criticism and sparked debate over the standard of judging at the show in general. The Telegraph in the UK has provide the following coverage:
Chelsea Flower Show 2013: top award is 'unfair' and should be scrapped, leading designer says
Chelsea Flower Show 2013: was 'Best in Show' unfairly awarded?
Chelsea Flower Show 2013: It's far from rosy at Chelsea, says judge over threat to resign

Back in Australia, a major new garden show has been announced. The inaugral "Australian Garden Show Sydney" will be staged in Centennial Park in September. Organisers aim to create a "showcase that will rival the world for its display of rare and amazing horticulture". That they think the garden industry and the public interest is sufficient to make a major show like this successful is encouraging. It will be interesting to see how it fares.

And back to the United Kingdom again, their Horticultural Trades Association have released their 2013 Garden Retail Market Analysis, an executive summary of which can be downloaded from their website here. Sales were down in 2012 compared to 2011, bad weather in the key month of April being blamed for a large part of the fall. Online sales and consumer confidence were also implicated.

The under-45 age group accounted for a disproportionate part of the decline. That falling numbers in this demographic are able to afford their own houses was pointed out, as well as the trend toward living in flats etc without a garden. One must assume that similar forces are affecting the garden market in Australia, land of grossly overpriced real estate.

We've also had our share of bad weather of various types arounfd the country. Will things ever get back to "normal"? Let's hope the organisers of The Australian Garden Show Sydney know something we don't!

The Tabebuias

In spite of their spectacular floral displays, this group of tropical trees is relatively unknown and under-used in Australia compared to Poincianas and Jacarandas. An article on the genus Tabebuia as ornamentals (they are also used for timber and medicine) was intended for this newsletter, but on delving into the subject I realised a short article could not do the topic justice.

Instead, the information has been collated into a webpage. If it's a subject of interest to you, take a look: This is possibly the most comprehensive overview on ornamental Tabebuias on the web at present, and will continue to be updated with more information, links and images over time.

The Science of Horticulture

Learning to live with Myrtle Rust

In 2010, a new fungal disease was detected in Australia - Myrtle Rust. Affecting plants of the family Myrtaceae, the potential for harm in Australia was enormous. Not only do myrtaceous plants constitute a very significant part of our native flora (including Eucalyptus), many industries such as forestry and apiculture are reliant on them. Many native and some exotic Myrtaceae are also widely used in ornamental horticulture in Australia.

So, how is ornamental horticulture coping with the myrtle rust threat so far? Should we even continue to plant myrtaceous ornamentals in Australia?

How bad is it?

Myrtle rust has spread extensively in Australia since it's first sighting, and at the time of writing, has been recorded on 143 species [1].

The good news is that, so far, the impact of the disease has not been as bad as initially feared, and the nursery and garden industry may be able to cope [2].


There are chemicals now registered in Australia for control of Myrtle Rust. While they may be useful in maintaining clean nursery stock, existing landscapes or valuable specimens, they are not a long-term solution to the problem. The general trend worldwide is to reduce use of chemicals and in the case of Australian natives, low inputs and environmental values are among the reasons to plant them.

Selection of resistant lines

Looking for resistance, whether in currently available cultivars or in the breeding of new ones, will be an important strategy for living with Myrtle Rust going forward.

Australian plant breeding and marketing company Ozbreed have been working with The University of Sydney to evaluate some of their myrtaceous lines for susceptibility to the rust. There was considerable variation across the range of species tested, and within species. Callistemon viminalis, for example, appears to be generally more resistant than some other Myrtaceae, but the seven cultivars tested tested exhibited a range of reactions from moderately to highly resistant [3].

Ozbreed stresses that susceptibility will also vary with environmental conditions. They recommend that in tropical and subtropical climates only resistant or highly resistant cultivars be planted, given the severity of rust infections in those regions.

Nevertheless, the results indicate that there is potential for future selection and breeding of new rust-resistant myrtaceous ornamentals. Many resistant cultivars may already be in the marketplace, but testing and promotion are required to give consumers confidence in using this material. Rust resistance could be used as a marketable feature, just as psyllid resistance has been for many lilypilly cultivars.

An alternative is to avoid myrtaceous plants altogether, but this would leave a big whole in the garden designer's palette, especially when environmental responsibility (e.g. providing food for native birds and insects) and utility (e.g. low water and fertiliser demands of many species) are important.

No doubt there are many under-exploited natives from other families which could be useful additions to cultivated landscapes, but selection, evaluation and commercialisation could take many years. This could be present an opportunity for some nurseries, however. It could also lead to greater diversity in the landscape, which is helpful in reducing the impact of any disease. Who knows what's around the corner?

The future

As myrtle rust is such a new disease, there must be much still to be learnt about it that could affect its management, besides further screening and breeding efforts. As far as the garden industry is concerned, the process of adapting to myrtle rust has only just begun.

Acknowledgment: Thank-you to Ozbreed Pty Ltd for providing information and feedback on this article.

References and Further Reading

[1] Myrtle rust Queensland Department of Agriculture, Fisheries and Forestry
[2] Cyclone Oswald another blow for embattled Queensland Comments by Donald Scotts, Nursery and Garden Industry Association of Queensland, published by Nursery World (Accessed 7 June 2013)
For the latest information on movement restrictions and control options, contact the appropriate government authority in your state. In Queensland, the Myrtle rust section of the Department of Agriculture, Fisheries and Forestry website is good place to start.
The Australian Pesticides and Veterinary Medicines Authority is also a source of information on registered chemicals, including their Public Chemical Registration Information System (PUBCRIS) database.
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