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Into Horticulture

Issue 15   April 2014

Plant & Garden News

Good gardens reduce crime

A study in Philadelphia has correlated well-maintained vegetation with lower rates of certain crimes such as aggravated assault and and burglary. This could be partly due to the calming effect of greenery on behaviour, and partly due to the strengthened sense of community leading to greater vigilance by residents. Furthermore, the message that people care about their community - and are watching - is communicated with well- maintained gardens and public spaces. Source: Study examines deterrent effect of urban greening on crime

Lignin biotechnology may revolutionise paper production

North American scientists have engineered poplar trees with modified lignin that makes processing for paper and biofuel easier and more environmentally friendly. Importantly, the strength of the trees was not adversely affected. Attempts to reduce the lignin content of trees by gene suppression have resulted in stunted or weakened trees in the past. Poplars are a useful species for growing on land not suitable for food crops. Sources: Poplars "Designed for Deconstruction" A Major Boon to Biofuels and Researchers design trees that make it easier to produce pulp

Trees green anti-depressants

A survey of Wisconsin residents has shown that, independent of social factors like age and income, those who lived in a neighborhood with less than 10 percent tree canopy were more likely to feel depression, stress and anxiety. The findings suggest a simple way to improve mental health in urban communities. Source: Wisconsin Research Shows Green Space Keeps You From Feeling Blue

Sugar dominant in branching mechanism

A new study in which scientists from University of Queensland were involved has challenged the long-accepted theory that auxin is the key regulator of apical dominance. Instead, demand for sugars appear to be primarily responsible. Tracking the movement of sugars with the radioactive C11 isotope (applied as carbon dioxide which was converted into sugars via photosynthesis), it was found that decapitation of the plant produced a rapid increase of sugar delivery to previously dormant buds. The sugars move about 100 times faster than auxin. which the researchers now believe plays a secondary role. The demand for sugar by growing apical shoots, limiting availability, may be what suppresses growth of lower buds. Source: Tracking Sugar Movement in Plants

Plants too, fight in the mating season

Examination of an Oxypetalum species (Apocynaceae) from South America has revealed horn-like structures on the pollinia (pollen sacs) with which appear to have no other function except to prevent the hooks which the pollinia attach themselves to pollinators becoming entangled with rival pollinia. Researchers think this is the first example in the plant kingdom of males physically fighting over a mate in a way comparable to many animals. Source: First evidence of plants evolving weaponry to compete in the struggle for selection

Urban gardeners lack information on soil contamination

One of the potential drawbacks of edible gardening in urban areas is the possibility the soil may have be contaminated from prior industrial uses or fallout from heavy traffic. A study conducted in Baltimore (USA), in which community gardeners were surveyed about their knowledge of these issues, has shown insufficient knowledge and expertise in assessing the risks of a site and how to minimise exposure to contamination that may be present. Source: Urban gardeners may be unaware of how best to manage contaminants in soil

New floral emblem for Bundaberg

The Golden Penda has been selected as the Bundaberg region's floral emblem. Besides the attractiveness of the flowers and foliage, its ease of cultivation in the region's conditions and the suitability of the tree for both private and public spaces was taken into consideration when making the decision. Golden Penda blossoms as Region's Floral Emblem

Study reveals unwelcome side effect of biochar

While stimulating marked increases in plant growth associated with brassinosteroids and auxin gene activation, a biochar study also showed that plant defence genes were suppressed by the soil supplement. This could have serious implications for the suitability of biochar for crop enhancement and carbon sequestration. Source: New study finds biochar stimulates more plant growth but less plant defence

Nitrogen and flowering in Phalaenopsis

A study on the use of nitrogen by Phalaenopsis (moth orchid) shows that adequate nitrogen fertilisation is required at all stages of growth for good flowering. The uptake and use of the nutrient throughout the growth cycle was followed by using the N15 isotope. It was found that a substantial amount of nitrogen taken up by the inflorescence was derived from fertiliser applied during flower development, but that some of the nitrogen applied in earlier vegetative growth stages also ended up in the flower spike. Source: Nitrogen source determined significant for inflorescence development in Phalaenopsis

What makes a petunia blue?

Researchers have discovered that if a newly-discovered type of cellular pump is defective, failure to acidify certain compartments (vacuoles) within petal cells makes petunia flowers blue instead of red or violet. The information may be useful in manipulating the colour in other flowers and fruits. Ways for plants to store toxic compounds within the vacuoles might also be developed. Source: Roses are red -- why some petunias are blue

Origins of Corn

The grass teosinte looks so different from corn that many have doubted the theory that it is the grain's ancestor. However, researchers growing teosinte under temperatures and carbon dioxide levels similar to those 10,000 years ago have observed more corn-like growth patterns. These characteristics were probably those expressed in the past and selected for by early farmers. Source: Greenhouse "Time Machine" Sheds Light on Corn Domestication

Rare tree sheds light on floral evolution mystery

Amborella trichopoda, a small tree from only one island in New Caledonia, has provided insights into the origin of flowers. This species is of significance because it is the only survivor of an evolutionary lineage tracing back to the last common ancestor of all flowering plants. The genome sequence indicates this ancestor arose following a doubling of the genome about 200 million years ago. Some of the duplicated genes then evolved new functions, including floral development. Genome doubling may therefore explain the relatively sudden proliferation of new flowering species. DNA of Storied Plant Provides Insight into the Evolution of Flowering Plants, Study Finds

Feature Article

The Gomphrenas

The button-like, papery flower heads of the ornamental annual Gomphrena globosa will be familiar to many readers, but compared to petunias and pansies, the genus hasn't received a lot of attention from breeders. This may be changing, however, with some significant new varieties released in recent years. We're likely to see more buzz about gomophrenas in the near future, so it's time to get to know them better.

Gomphrena species belong to the family Amaranthaceae, which contains a variety of edible, ornamental and weed species. Ornamental Amaranthaceae include Amaranthus and Celosia as well as Gomphrena. The recently commercialised Australian native Ptilotus is also a member of this family.

The "flowers" of Gomphrena species are actually a cluster of papery bracts between which the tiny true flowers are borne. New bracts and flowers are developed at the tip as old ones fall away, meaning the "flower" can last quite a long time on the plant.

Narrow leaves borne on branching stems with long internodes mean the larger types, if given space, form an attractive low bush of airy foliage, especially if given a bit of tip pruning early on.

Gomphrenas love heat. They can also tolerate some dryness, are relatively pest and disease free and have a long bloom preiod. These qualities help explain why the genus is making inroads in the bedding plant scene, given our increasing need to reduce water, chemical and labour inputs.

While well suited to traditional garden styles, the unusual "architectural" form of both flowers and overall plant habit means they are not out of place in more contemporary designs.

There has also been an surge of interest in butterfly gardens in recent years, and gomphrenas are popular to include as a nectar source.

What's more, they are suitable for cut flowers, either fresh or dried. With so many admirable qualities, it's little wonder they're becoming so popular.

Gomphrena globosa

Commonly known as globe amaranth or bachelor buttons. Generations of gardeners have valued this annual for its ease of growth, especially in hot conditions. It is believed that globe amaranth originated in India and was introduced to America in 1714 [1].

Some well-known G. globosa strains include Buddy and Gnome. Some of the QIS series are G. globosa. Globe amaranth is a facultative short day plant [2].

Gomphrena haageana

While G. globosa varieties come in the white/pink/purple colour ranges, G. haageana is notable in the orange/red spectrum. It originates from the southwest of North America and has been cultivated since the mid 1800s [1].

The growth habit is also larger and can last more than one year in a suitable climate. The longer stems make it more suitable for commercial cut flower production.

Best known form is 'Strawberry Fields', with a orange-red flower heads that look a little like strawberries. It has been in cultivation overseas since the 1920s at least [3]. Other red and orange selections are also commercially available as part of the QIS Series. There's a lavender variety in the US.

Gomphrena Fireworks

Marketed as having "more blooms per plant than other gomphrenas", and a "scaffolding" habit [4], the arrival of Fireworks around 2009 did a great deal to increase interest in the genus.

Those who have grown it rave about its toughness, prolific blooming and its stunning visual effect. It can reach over a metre high and wide, with flowers held aloft on long stems. It can be cut back to return the following year if not killed by cold.

The floral bracts are hot pink, complimented by the tiny gold flowers protruding from within. Given the popularity of this plant, we might expect new colours to introduced into this line in the future. It has been introduced in Australia but it may be still hard to find here.

Gomphrena Pink Zazzle™

Also hot pink, this new hybrid is smaller and more compact than Fireworks, with fuzzy leaves. Large flowers, good branching and daylength-neutral flowering are key features being promoted in addition to all-round toughness [5].

Gomphrena Pinball™

Another new release, this is the first vegetatively propagated Gomphrena series. These hybrids are touted as having "unique texture, mounding habit and continuous flowering" [6]

It's unlikely that Pink Zazzle and Pinball are yet available in Australia, but gardeners may wish to keep an eye out for these and other new varieties in coming years.

Australian Gomphrena

There are many species native to Australia, with some attempt made to introduce selections into commercial trade. These include G. leontopodioides 'Empress', G. leontopodioides 'Balboa' and G. flaccida 'Pink Gem'. Gomphrena canescens is another species with ornamental potential.

While these have yet to achieve widespread popularity, it's possible that they might get fresh attention with the surge of interest in the genus. Furthermore, these and other Australian natives could also be a source of useful traits in future hybridisation programs.

Gomphrena Weed

A review of garden gomphrenas wouldn't be complete without mention of the common weed G. celosioides. It's a low-growing, drought tolerant pest plant with a white infloresence of a form typical of the genus.

References and further reading

[1] Globe Amaranth - Plant of the Week University of Arkansas
[2] Light and flowering of bedding plants Michigan State University
[6] Pinball™ Sakata Ornamentals

For more background information see the list of links on
     Gomphrena Strawberry Fields
Young inflorescences of 'Strawberry Fields'
Gomphrena Strawberry Fields
The tiny true flowers are produced between papery bracts
Gomphrena Strawberry Fields
New flowers and bracts continue to be produced from the tip the inflorescence over an extended period
Gomphrena celosioides
The weed species Gomphrena celosioides

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