As the Gardener's HQ website covers many species of plants, from many different countries, it is likely that some of the plants covered may be considered a weed in your area.
Please be aware that though they may be invasive in your area, that they may make ideal garden plants in other areas which have different climates.
I therefore feel justified to include species that may be considered a pest in many parts of the world.
I do however strongly agree that gardeners need to be aware of which plants are invasive in their own areas, and that they should avoid growing plants that may be problematic to the balance of their local ecosystem.
For many species that are invasive it can be a good idea to grow the native species that they have outcompeted so that you help with their natural recovery
That said in some areas the native plants do not stand a chance against the invasive species, in this case you may wish to consider growing a similar type of plant. One that does not grow aggressively but still grows well. Sometimes you may need to grow a completely different genus of plant to compete with the invader.
Below are some links to information on invasive plants below.
http://www.invasivespeciesinfo.gov/
Preventing the spread of invasive plants in teh UK
http://en.wikipedia.org/wiki/List_of_invasive_species_in_Europe
http://en.wikipedia.org/wiki/List_of_invasive_species_in_Asia
http://www.invasivespeciesinfo.gov/ - Asia
http://www.iewf.org/weedid/index_by_reserve.htm
http://www.doc.govt.nz/ - New Zealand
Invasive Species in South Africa
http://www.invasivespeciesinfo.gov/international/southamer.shtml
Plants such as the Plume Poppy of the Macleaya genus are considered invasive in many areas, but may struggle to grow in other areas. Photograph by Leonora Enking.
I hope that you find the above information useful and that you carefully consider which plants may be invasive when you are planning what to grow in your Garden.
For more Gardener's HQ gardening articles go here.