What is a weed?

A weed is an unwanted species, for reasons including:

Introduced alien species

Competes with agricultural crops

Volunteer crop species

Contamination of crop harvest

Contamination of animal products

Affects the operation of farm machinery

Injurious to livestock and wildlife

Injurious to humans

Host plant for pests

Host plant for diseases

Provides shelter for feral animals




Invades grazing land

Low nutritional forage value




Changes soil chemistry

Increases soil erosion


Damage to property and infrastructure

Degrades habitat for native plants and animals

Climbing or smothering growth habit

Decreases recreation opportunities

Fire hazard 

Impacts on waterways and water resources

Deprives people and ecosystems of  water resources

Clogs irrigation channels

Clogs drinking, irrigation and hydroelectric power water pipes.

Blocks navigation and flood control

Invades marine environments

Scientific Names

The World Flora Online (WFO) used as the reference for most of the "accepted" species name (prior to June 2023 The Plant List had been used)

We also include ~7,000 commonly used synonyms (aka = also known as)

If you are looking for a name that is not listed please contact us so we can considering adding it

Family Names

Since authorities can use different family names, we have included family names from The Plant List, International Plant Names Index (IPNI) and US Department of Agriculture

We have given a priority to "eae" endings for consistency, and list alternative names as aka for the common families:

Apiaceae aka Umbelliferae
Asteraceae aka Compositae
Brassicaceae aka Cruciferae
Fabaceae aka Leguminosae
Lamiaceae aka Labiatae
Poaceae aka Gramineae

Priority given to the most commonly used family name

Where species have been reclassified, or families re-assigned, we include previous family names as aka because many sources continue to use the names

Common Names

The database currently has 100,000+ common names (in a number of languages)

The greatest number are English (~30,000) - French, German, Spanish (~6,000 each) - Chinese (~5,000) - Russian (~3,000) - with lesser numbers for other languages

We will add a facility for users to easily contribute more common names and when we have a sufficient number, you will be able to search for species by a "local" common name

See More Info (ie. links to other websites)

KYW does not currently provide "fact sheets" for species because there are usually other on-line sources that already have relevant species information

These links are to external websites and KYW is not responsible for any content

If you know of other websites with useful information, please contact us

My Weeds

Any data or text you add to your My Weeds™ library remains your copyright property and KYW does not in anyway use or share this information with other parties except to store the information so that you can access it

Photographs - Copyright & Creative Commons

The photographs displayed on this site have been sourced from photographers who have given permission for KYW to use their work, or who have licenced their work under a creative commons licence, or works that are in the public domain

Please note that the licencing information provided by KYW is based on information as at the time of image download and should not be relied upon for current licencing

If you intend to use any photographs it is your responsibility to visit the original source and to make your own determination as to licencing arrangements

Photographs by KYW have a CC BY 4.0 licence and can be downloaded from the site


At present the site text content is in English and we plan to translate other languages in the future

We have already done some translations and provide basic site navigation and species info in 40+ languages

We used Google translate to generate the initial translations and then verified translations using "local" language sites - we apologize in advance for any inaccuracies and welcome your feedback regarding any corrections or improvements

Privacy & Security

Your account login details are managed off site by Auth0 - a specialist application to ensure the protection of your user identity and password

Subscription payments are managed by PayPal - KYW does not store your payment details

The database and website is hosted by Amazon Web Services (AWS) to ensure industry standard levels of accessibility, security and backup

Countries & Regions

Since most countries do not have a published list of weed species, KYW has used a sampling methodology to arrive at lists of species by region (with the exceptions of Australia and New Zealand)

When searching you can select your country to find your region, or select a region to see what countries are included

KYW will be further developing country (and state/province) level data and welcome feedback from weed societies and/or accredited academic teams who are interested in helping to provide local intelligence

In the News

We collect news articles about weeds and update the database each month

These are links to external websites and KYW is not responsible for any news content

Please note - some sites have a limit on the number of articles you can view (usually per month) - and some sites have short surveys that you must answer to get access - this data is collected by the news site and not KYW