21st June 2005

 

A WONDERFUL WEED WITH A STRETCHY STEM

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Cleavers, goose grass and Sticky Willy are all common names for a rather annoying, sticky plant which clings to your trousers and sticks to your dog’s fur on country walks.

 

Its adhesive properties are well known, but now researchers at the University of Lincoln have discovered another special characteristic of this extraordinary plant – it has an amazingly stretchy lower stem.

 

Galium aparine is a member of the Bedstraw family known for its persistence as a troublesome agricultural weed; its small seeds can contaminate grain and the long stems can become entangled in combine harvesters.

 

But cleavers also have beneficial characteristics: historically it has been boiled as spinach before the two-seeded fruits appear and in Sweden the seeds are roasted, ground and used as a substitute for coffee. 

 

The green seeds were also once used to adorn the tops of lacemakers’ pins to provide a padded head.

 

Until recently research into this species has largely focused on its commercial importance as an agricultural weed, but researchers at the University of Lincoln have discovered that the plant has a highly extensible and relatively elastic basal stem.

 

Under laboratory conditions the lower stem stretched by up to 24 per cent of its original length before breaking.

 

“This is rather unusual for a terrestrial plant and it is only in aquatic species of the buttercup family and some seaweeds where similar mechanical behaviour has been observed,” said Dr Adrian Goodman, who is a lecturer at the university.

 

“The inspiration for the study came from a chance meeting I had with the plant when walking around the university campus.

 

“I noticed that cleavers had rather peculiar properties when I tried to remove some of the stems which had become attached to my trouser legs.”

 

As yet the researchers are unable to pinpoint how the plant stretches so much, but they have a better idea of why it should do so.

 

“It may be that the stems are better able to cope with sudden tugs, in a similar way to the stems of aquatic plants which cope with changes in flow rate in their watery environment,” said Dr Goodman.

 

“Indeed, cleavers are commonly found scrambling up hedges and attached to upright species such as grasses, and they may have evolved in such away as to minimise the effects of a support which sways in the wind.

 

“Furthermore, this species is known to be dispersed by animals – the hooked seeds are frequently found attached to their fur – so the stretchy lower stem may have evolved as a mechanism to help prevent the plant from being uprooted.”

 

So when you are next weeding in your garden, walking by a hedgerow or removing the hooked seeds from your pet’s fur, pause for a moment and take time to ponder about this intriguing plant and its rather remarkable stem.

 

Go to picture 1

Dr Adrian Goodman checks out the stretchy stem of Galium aparine, or Sticky Willy

 

Go to picture 2

A close up of the bristly two-seeded fruit of the cleavers

For more information contact:

Jez Ashberry, Press and Media Relations Manager

01522 886042                         jashberry@lincoln.ac.uk

Visit our news web pages:      www.lincoln.ac.uk/news/latestnews.htm