This bouquet may look beautiful, but the weeds are killing our native plants

A bouquet featuring some of the worst invasive weeds in Western Australia's South West has won a top award at the Margaret River Agricultural Show.

Nature Conservation Margaret River entered the unusual floral arrangement in a bid to raise awareness of the environmental damage caused by invasive weeds, including plants commonly found in home gardens.

The bouquet featured arum lilies, English ivy, watsonia, Flinders Range wattle, agapanthus, periwinkle and Victorian tea tree.

Margaret River Agricultural Show vice-president Julie Kirby said there had been a record-breaking 200 floral exhibits across several individual categories, including roses, wedding bouquets, mixed arrangements, floral art, and mixed weed arrangements.

Nature Conservation Margaret River's entry was awarded ribbons in the mixed weeds category and best overall exhibit.

"The best exhibit is one that really catches the judges' eyes," Ms Kirby said.

"We have trained and accredited judges from the Western Australian Horticultural Council and they thought that the overall design, the workmanship, and the colour harmony and the quality and the condition of this particular display was just so impressive.

"With the mixed weed arrangement you don't need to grow it yourself, you can go and collect it from bushland or the roadside, or wherever you've got weeds present and enter them."

She said the bouquet was disposed of safely to prevent the seeds from spreading.

"It was a beautiful and educational way to show how garden plants can escape to become bushland weeds," Ms Kirby said.

Nature Conservation Margaret River biodiversity officer Obelia Walker said the organisation saw the competition as an opportunity to draw attention to some of the region's most problematic invasive plants.

She said she was surprised to discover the arrangement had taken out the overall bouquet award.

"I didn't realise that I'd actually won the champion bouquet for the whole category," Ms Walker said.

She said the judges recognised the arrangement as a creative way to get the community thinking about the threat posed by invasive weeds.

"Weeds are sometimes a tricky one to get people to pay attention to," Ms Walker said.

"They really take over and smother all our lovely native plants.

"Arum lily, of course, can just become such a monoculture and a carpet, but the others can as well."

Invasive plants thrive in the South West

The arum lily, considered one of the most damaging weeds in the country, was banned from sale in WA more than 20 years ago, but the rogue garden plant's infestation of forests across WA's South West shows no sign of slowing.

More than 3,000 private landowners have requested help to eradicate the weed on their properties.

Ms Walker said invasive weeds often thrived because they had no natural predators encouraged gardeners to consider alternative plants rather than risk introducing invasive species into the environment.

The organisation hopes the unusual prize-winning bouquet will encourage people to look more closely at what they are planting in their backyards.