CSIRO Media Release 94/58
12 July 1994


WILLOWS AND SEX: CALL FOR WILLOW IMPORTATION BAN

Recently imported willow varieties could choke Australian rivers, 
according to Mr Kurt Cremer of the CSIRO Division of Forestry.  

'The new varieties are hybrids of Salix matsudana x alba . Both male and 
female trees have been introduced to Australia from New Zealand', Mr 
Cremer said.  'The females should not be planted as their seed can float 
for long distances on even the slightest breeze'.

'If seeds spread as they have done in New Zealand many of our waterways 
could be blocked by thickets of willows' he said.

All willows in Australia have been introduced from overseas, usually as 
cuttings.  There are a number of varieties, but until recently each 
variety was either all male or all female.  The spread of willows was 
predominantly by deliberate planting of cuttings or by pieces broken from 
existing plants taking root and establishing in new locations.

Mr Cremer said that in New Zealand, two willows, present as both sexes, 
have spread aggressively as seedlings in river channels in the Canterbury 
region and in swamps throughout the country.  'If we wait until we have 
that problem it could be too late to deal with it effectively', he said.

'A thorough investigation is needed to determine which new willows, if 
any, should be allowed into Australia', Mr Cremer said.

Willows are valuable in some cleared Australian landscapes, especially 
where natives are impossible or very difficult to grow satisfactorily.  

Mr Cremer said, 'They are cheap to reproduce - just push a stick into 
moist soil. The trees form dense mats of rootlets at and below water 
level which is particularly useful along rivers to stabilise banks and 
reduce erosion. We need, however, to prevent their uncontrolled 
introduction and spread' he said.

More information from:
Kurt Cremer 064-533235 		Mick Crowe 06-2818357