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Weeds

What is a weed?

The definition of a weed can be defined as:

• A plant growing where it is not wanted
• A plant out of place
• A plant that is more harmful than beneficial

Any plant can be a weed in a given circumstance. Kentucky bluegrass that spreads into a flowerbed is a weed; a poisonous native plant in a livestock pasture is a weed. A plant is a weed only in terms of its impact on human activities.

What is a noxious weed?

A noxious weed is a non-native plant from Europe or Asia that is placed on the Montana State List because it:

• Decreases the economic value of land and crops
• Decreases forage for livestock and wildlife
• Displaces native plant species
• Lowers plant diversity
• Increases soil erosion and sedimentation
• Affects recreational value

What is a native plant?

A native plant is one that has established naturally without human intervention and has existed for many years in a specific region or area. Native plants in Montana are those that grew in North American prior to European settlement.

Why are noxious weeds invasive?

There are many theories about why noxious weeds are invasive. When they came from Europe and Asia they left behind natural predators, like insects and grazing animals, parasites, and diseases which would control their rate of spread and growth. Plants referred to as noxious weeds also have characteristics that give them the ability to spread and compete well with many cultivated and rangeland plants. Most major weeds have at least several of the following characteristics:

• Continuous seed production for as long as growing conditions permit
• Unique ways of dispersing and spread, including vegetative propagation and seed production
• Ability of seeds to remain dormant in soil for long periods of time
• Ability to grow under adverse conditions
• Adaptation to a wide variety of soil and climatic conditions
• Compete well for soil moisture, nutrients, and sunlight