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Into Horticulture

Issue 4   August 2011

Plant & Garden News

Historic tree vandalised
Mackay's National Trust listed Leichhardt Tree has been vandalised. It appears to have been attacked with an axe or similar sharp object. Located on Bluewater Quay, sailing ships were tied to the tree in the early days of Mackay before the wharves were built. Police are investigating. Source: Violent act taken out on the region's historic Leichhardt Tree

Plants never sleep
Did you know that the stems of most plants tend to grow most at night? While it is still unclear why plants do this, scientists have come closer to understanding the mechanism. Three genes produce proteins that interact to form an "evening complex" which suppress certain growth genes during the day and early evening. Source: Biologists discover an 'evening' protein complex that regulates plant growth

The Nursery Effect
The belief that plants behave differently depending on the nursery in which they were raised - a "nursery effect" now has some scientific support. In a Canadian study, cuttings were taken from genetically identical poplar trees grown in two different regions. Even though this generation of trees were raised under the same conditions, they subsequently responded differently to drought stress. Furthermore, it was shown that different genes were activated. This suggests the performance of plants in the landscape could be affected by the way the stock plants used for the cuttings were treated. Source: New research shows forest trees remember their roots

Plant hormone discovery has horticultural potential
Strigolactone, discovered at the University of Queensland, could be used to manipulate the size and shape of plants by controlling branching. The chemical suppresses branch development, which could be advantageous in forestry. On the other hand, repression of the chemical could encourage branching, which is often desirable in orchard production and other horticultural applications. Interestingly, the chemical is quite similar to one called karrikins from smoke, which stimulates germination of some seeds (but does not affect branching). Source: Plant branching hormone discovered

Macadamia's Qld ancestry to be explored
Samples of from some of the few remaining wild macadamias in SE Qld and NNSW are being collected for genetic analysis for use in ongoing development of the crop. The first nuts taken to Hawaii in 1982 by Captain Jordan, which led to the macadamia becoming an internationally valued nut crop, came from Pimpama. One of the goals of the current research is to confirm whether "The Jordan Tree" on the Gold Coast is actually the ancestor from which the Hawaiian cultivars were developed. Source: Geneticists seek mother of all macadamias on the Gold Coast

Small leaves confer drought tolerance - but why?
Scientists studying the evolutionary advantages of small leaves in arid environments believe it may be due to the greater relative density and length of major veins in the leaf tissue that results. This helps to ensure adequate water flow even if air bubble forms in the veins (embolism) during drought. Source: Being small has its advantages, if you are a leaf

A new type of plant tag
Microchip technology similar to that used to identify animals is being tested in plants. Scientists in Italy have developed a way to embed Radiofrequency Identification (RFID) tags in rose bushes that causes minimal damage. Potential applications of such technology include tracking of plants for research or quarantine purposes, identification of valuable specimens vulnerable to theft, and visitor guides in botanic gardens. Media releases including link to original HortTechnology article: Embedding microchips in ornamental shrubs

Maritime technology seed inspired
Seed of the palm Dypsis rivularis have inspired the development of a coating that could replace the toxic anti-fouling paints currently used on ship hulls. It was suspected that the seeds, which are dispersed by ocean currents, might prevent marine organisms from colonising them by having a hairy micro-structure that is constantly moving. Initial attempts at an artificial surface mimicking the of the seeds' surface are promising. Source: Specialized seeds can really float your boat

Making Anthurium blue
Flower colour is determined not only by the chemical pigments present, but other aspects of cell chemistry and structure. Scientists at the University of the West Indies have been studying pH in the vacuoles of epidermal cells in the spathes of Anthurium andraeanum. They found that generally, the lighter the colour the higher the pH. The eventual goal is to expand the current colour range by engineering blues into the species, which requires a suitable pH environment. Media release including link to the original "HortScience" journal article: Engineering blue-hued flowers

Bundaberg rain garden could be first of many
A bio-retention basin has been constructed to reduce runoff from Bagara Streetscape. Besides helping to protect Burkitts Reef from contaminated water, the "rain garden" provides urban green space and biodiversity. This is the first raingarden in the region, but Bundaberg Regional Council anticipates that more will be built in new developments. Source: First rain garden in region will benefit coastal environment

Ginger could be new weapon against fruit fly
With chemicals dimethoate and fenthion under review by the Australian Pesticides and Veterinary Medicines Authority, researchers at the Queensland University of Technology are looking for alternative ways to control Queensland fruit fly. One potential method involves using an extract of ginger called zingerone to lure male fruit flies into traps. Source: Qld fruit fly scientists in race against time

Ferns fight formaldehyde
It has been known for some years that indoor plants can combat the effects of indoor air pollution. Scientists have tested the ability of 86 diverse species of plants to remove volatile formaldehyde. They found that, as a class, the ferns were the most efficient, with Osmunda japonica (Japanese royal fern) coming in first amongst all 86 tested. Media release, including link to the original American Society for Horticultural Science article, here: Study of phytoremediation benefits of 86 indoor plants published

A new wave in weed control
Australian research is working towards a weed-killing device that uses microwaves instead of chemicals. Energy could be focused on individual plants, making it potentially useful for spot-treatment. It would not be affected by wind or rain or leave herbicide residue. Making the system more energy-efficient will be one of the aims of future research. More information from the Rural Industries Research and Development Corporation: Microwaves to cook away weeds

Editorial - More gardening on TV, please!

If you watch TV at all, you must have noticed the proliferation of renovation and real estate shows screening lately. Is it just a coincidence, or does it say something about the real estate market? Perhaps it signals a renewed focus in home and family life as a response to what's happening in the global economy?

Whatever the cause, such shows help to promote some of the benefits of an attractive landscape to the public. One of the limitations of a makeover-style program, however, is that there is a limit to what can be achieved in the garden in the extremely short time frames they usually operate in.

In real life, however, not everyone wants to flip a house in a few weeks. If there is more interest in enhancing our lives at home, maybe it's about time for a new program on free-to-air television that's 100% dedicated to gardening.

How about it, TV networks and industry associations?

Spring events

Springtime is here! Besides enjoying your own garden, be sure to take advantage of some of the many garden shows and open gardens at this time of year. If you live in this Queensland, check

If you're in charge of organising such an event, it's not too late to send in some details for free inclusion in the diary. Many municipalities hold garden competitions at this time of year, and if you're organising tours of winning gardens, you're welcome to send in information about those, too.

Kate (left) and Helen help bring damaged gardens back to health
Feature Article

Volunteer group restores flooded Brisbane gardens

Brisbane Garden Recovery started with the chance meeting of two garden enthusiasts at the Yeronga Recovery Centre in the aftermath of January's devastating floods.

With small children in tow and armed with donated plants and mulch, Kate Wall, Helen Hynd and a small team of volunteers attacked mud, weeds and dying plants with gusto. To date, the group has restored over 150 gardens through 12 suburbs.

Their work not only brings life back to badly damaged gardens, it also has aided the garden owners in their journey to recovery. With control of their gardens back, "floodies" are also given the gift of hope, raised spirits and the empowerment to keep on gardening.

The group operates entirely on donations. Council has helped with mulch, and Neutrog Fertilisers have donated all the fertiliser. Plants have all come from private donations or nursery seconds.

More plant donations are needed desperately! If you have cuttings, spare plants or garden supplies or nursery seconds, they would love to hear from you:
       FACEBOOK: Brisbane Garden Recovery

Acknowledgement: Thank-you to co-founder of Brisbane Garden Recovery Kate Wall, who supplied the information above. Kate now runs local gardening business The Gardeners Wall
For Your Virtual Library

Plants in Action  An online plant physiology textbook available at the University of Queensland website. Published by the Australian Society of Plant Scientists, New Zealand Society of Plant Biologists, and New Zealand Institute of Agricultural and Horticultural Science

The Plant List A database of nomenclatural information that aims to include all known plant species. An international collaborative effort that draws on databases help by several botanical institutions.

Mansfeld's World Database of Agriculture and Horticultural Crops Information on over 6000 crop species

The Science of Horticulture

Seed Dormancy (Part 1)

Raising plants from seed is a fascinating and satisfying aspect of gardening. On a more practical level, it's a necessary skill if you want to fill a vegetable garden cheaply and it provides options for obtaining a variety of ornamental plants that might be otherwise unprocurable. Professional growers, of course, produce many plants (or rootstocks) from seed as a cost-efficient propagation method.

Seed raising isn't always straightforward, however. If your efforts aren't successful, don't necessarily assume the seeds are dead or that your skills as a propagator are to blame. The seeds could simply be dormant.

Seed dormancy factors affect the speed and uniformity of germination, and have implications for seed storage. Therefore, an understanding of dormancy can be useful for anyone involved in raising plants from seed.

Not all seeds have dormancy factors. Some will sprout provided environmental conditions (moisture, oxygen, temperature etc) are suitable for growth.

Many plants, however, employ dormancy mechanisms. In some cases, the seed may require quite particular conditions that make germination difficult to achieve in an artificial environment, but this is not in itself dormancy (although it may be just as frustrating for the gardener). Botanically, dormancy is a "block" or "lock" on germination.

Depending on the species, dormancy may reside in different parts of the seed such as the embryo, the endosperm or the seed coat and more than one type of dormancy can operate on the seed at the same time.

Some forms of dormancy:

Impermeable seed coat - The propagator can mimic the natural action of abrasion, fire or an animals' digestive systems with seed treatments such as cutting, sandpaper, heat or acid, a process known as scarification.

Chilling or warming requirement - A temperature treatment (usually applied with moisture) to overcome dormancy is called stratification.

Presence of chemical inhibitors - These need to be leached away or degraded. (Inhibitors sometimes occur in the fruit tissue surrounding seeds, also).

Requirement for chemical triggers - For example, many fire-adapted species respond to substances in smoke.

Light requirement - Amount and/or wavelength of light can either inhibit germination or stimulate it. Whether a seed is buried, exposed or shaded by a competing plant has obvious implications for its chances of survival in various habitats.

Embryo immaturity - after being shed from the mother plant, the embryo may require further development inside the seed before it can germinate.

A wide range of dormancy mechanisms exist in the plant kingdom. In a given species, these may apply individually or in combination. In the latter case, dormancy-breaking treatments may have to be applied in a particular order for germination to proceed.

Just to complicate matters further, dormancy may vary from one batch of seed to another, and unfavourable environmental factors can induce dormancy in seeds that weren't dormant before (secondary dormancy).

More about seed dormancy, with links to further reading, in Part 2 of this article in the next newsletter

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