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Horticulture 1000
HT1102 - Plant management 2 - Weeds
Fertiliser Weed control
2

Weeds

A weed is an unwanted plant that is growing in the wrong place.

Weeds:

Weeds will compete and slow down the growthWeeds will compete and slow down the growth of carrots growing in this garden.
The result will be smaller sized carrotsThe result will be smaller sized carrots.
 

Why weeds are successful

Weeds have characteristics that let them grow successfully in harsh conditions.

Thistles produce hundreds of seedsThistles produce hundreds of seeds, which are blown by the wind and spread widely.

Weeds (especially annual and biennial weeds) produce many seeds, and each seed can produce a new plant.

 
Couch grass has tough, stringy rhizomes – each can grow into a new plantCouch grass has tough, stringy rhizomes – each can grow into a new plant.

Weeds have runners, bulblets and other asexual means of reproduction. Perennial weeds become established very quickly and are difficult to destroy.

 
The dock has a strong taprootThe dock has a strong taproot.

Weeds grow and become established quickly and strongly. New plants can grow from pieces of dock root as well as from the seeds produced.

 
Dock root is very difficult to pull outDock root is very difficult to pull out.

Here is an example of a dock root. It is very difficult to pull out.

 
Gorse seed has been known to last for at least 20 years in the soilGorse seed has been known to last for at least 20 years in the soil.

Weeds have seeds that stay viable for a long time. The seeds can sit in the soil for years. They germinate when the right environmental conditions prevail.

 
Stinging nettle has little spines that cause irritationStinging nettle has hundreds of little spines that cause irritation to the skin when touched.

Weeds have protective mechanisms that prevent them being eaten by animals.

 

Weed identification

Weed identification is useful when looking at the best method of control. You can do this by:

Complete Activity 2A in your workbook

Key points   Key points

  • A weed is an unwanted plant that is growing in the wrong place.
  • Weeds compete with useful plants, reducing their growth and harbouring pests and diseases.
  • Weeds are successful because they can produce many seeds that can last for a long time; they have efficient asexual methods of reproduction, grow vigorously, and can have protective mechanisms.
 

What's next?

Go to: 3 Weed control.

Fertiliser Weed control