Weed Information

Weed Information -Weed Ecology

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How do weeds spread?

Seed dispersal

Seeds are scattered and spread into new areas away from the parent plants in 4 main ways:

 1) Wind: some seeds have a shape adapted for being carried by the wind. (weeds = sycamore seeds have 'wings', dandelion seeds are attached to tiny feather-like parachutes, feathery pampas seeds)   sycamore
 

2) Water: seeds and fragments of stems from plants living close to waterways are transported by rivers, streams and sea to new areas (weeds = willow twigs, wandering jew/tradescantia)  

3) Animals: Seeds inside fruit attract animals such as birds or lizards, which eat the fruit and fly/run off with the seed inside their gut, and eventually the seeds are passed out of the gut unharmed in the animal's poo! (weeds = privet, woolly nightshade , kiwifruit) . Some seeds, such as bidibids have hooks and attachment that help the seeds stick to animal fur or sheep's wool.  

kereru

4) The plant itself! Some plants have seed pods or seed heads that burst open, catapulting the seeds away from the adult plant (weeds =  broom & gorse pods)  

seed

Vegetative dispersal

This is where the weed spreads not by a germinating seed and seedling, but by methods such as brittle stems that break easily (or fragment), re-sprout and take root where they land (e.g., wandering jew/tradescantia, crack willow) - making new individual willow or tradescantia plants. Other weeds have long roots or runners that can produce shoots away from the mature plant. (e.g., strawberry, blackberry).

Humans give weeds a helping hand....

weeding child

don't spread weeds - pull them out!

  • Some people do not know enough about the dangers of weeds to our environment or livelihoods and encourage weeds unintentionally. For example, some people dump garden rubbish on roadsides or in the bush, thinking that it is biodegradeable. They don't realise they could be starting a weed problem.
  • In some places, weedy plants are still being sold in nurseries and planted in gardens because they are pretty.
  • Aquatic weeds are sold in pet shops for aquariums and backyard ponds. Some of these plants escape to natural areas, such as rivers, creeks and lakes, especially when people dump the contents of fishtanks into waterways.
  • Some seeds sold in bird-seed mixes are weedy and may escape the bird's beak!
  • Cars, 4WDs and mountain bikes can carry plant fragments (e.g., wandering jew/tradescantia) or seeds in their tyres, bumpers, mudflaps or undersides.
  • Trampers can transport seeds on boots or clothes.
  • Increasing tourism, trade and transport mean seeds and plant material are now moving between countries more often, and some may slip into NZ accidentally in shipping containers or planes.
  • Many aquatic weeds spread vegetatively, by fragmentation. A small piece attached to a propeller or trailer wheel can infest a healthy lake!
  • Many of the world's worst weeds can now be bought through the internet! 
weeding child

clean up your weedy backyard! 

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Weeds in New Zealand