Gardens: what to do this week

Hardy perennial Hellebore ‘Slate’. Photograph: Dave Zubraski/Alamy

Pickle this

If your food waste goes to landfill, you’re missing a great soil improver. A bokashi system lets you collect and ferment it using beneficial micro-organisms: it’s easy, quick and compact, plus the runoff (or bokashi juice) is great for keeping sinks and drains “sweet”. Put the fermented waste in your heap or wormery, or bury it in the soil. For a bokashi starter kit, try evengreener.com.

Visit this

How many cherry trees can you name? I bet it’s one: ‘Morello’. The Cherry Fair at Brogdale Farm in Kent on 19 July aims to open our eyes to a world of cherries, from ‘Stella’ to ‘Merchant’. Taste and buy more than 30 varieties, and find out how to coax a great crop from your own tree.

Plant this

Come spring, you’ll be glad you planted up that unloved shady corner. Hardy perennial Hellebore ‘Slate’ has pretty, purple-black blooms from February to April, and would look good with lime-green euphorbias or white pulmonarias. Height and spread: 40cm x 40cm. Buy one H. ‘Slate’ in a 9cm pot for £11.99 (including free mainland UK p&p). To order, call 0330 333 6856, quoting ref GU357, or go to our Readers’ Offers page. Dispatched in July and August.

Scientists discover why some roses smell sweeter than others - and how to improve the scent

A Damascus Rose

Not all roses smell that sweet but scientists have found out why some smell sweeter than others and in the process have discovered a way of potentially improving the scent of the gardener’s favourite ornamental flower.

A study into the chemistry of rose scents has found a new biochemical pathway in the petals of the plants which produces a sweet-smelling fragrance that could be re-introduced into rose varieties that have lost their smell.

Scientists have identified an enzyme known as RhNUDX1 which plays a key role in producing the sweet fragrance of roses, which they suggest could be re-introduced into modern varieties that have lost their scent as a result of intensive breeding for better colour and shape.

Jean-Louis Magnard and colleagues from the University of Lyon in St Etienne in France identified the new source of rose scent in a study published in the journal Science that investigated the source of the strong scent in the rose Papa Meilland.

They found that the enzyme was lacking in another rose, called Rogue Meilland, which produces little scent and a genetic analysis revealed key differences in the genes responsible for the biochemical pathway that led to the synthesis of the enzyme.

The researchers found that the RhNUDX1 enzyme, which works in the cells of the flower petals, generates the well-known fragrance substance called monoterpene geraniol, the primary constituent of rose oil.

In the future, it might be possible to exploit the knowledge about the gene for RhNUDX1 in order to breed pleasant-smelling scents back into modern varieties that lack a strong fragrance, they said.

Rose Flower pictures

Scientists believe that the discovery of a new biochemical pathway that can synthesise rose scents is probably due to the independent evolution of chemical attractants designed to advertise flowers and bring pollinators to fertilise them.

It is known that a single constituent of rose oil, such as rose oxide, can impart different scents depending on which 3-D shape they have formed. Rose oxide, for instance, can produce four different scents, sweet, fruity, minty or citrusy, depending on which one of four 3-D shapes it has formed.

A version of this article appeared in the print edition of The Daily Star on July 03, 2015, on page 11.