Note that at higher altitudes, this could be the native dandelion, Taraxacum aristum.
Environmental weed in NSW and Vic (as Taraxacum officinale).
http://keyserver.lucidcentral.org/weeds/data/media/Html/taraxacum_officinale.htm
Taraxacum sp. is listed in the following regions:
Canberra & Southern Tablelands | Southern Highlands | Albury, Wodonga | South Coast | Greater Sydney | Gippsland
Synonyms
Taraxacum officinaleMaps
ANU Daley Precinct Aranda Bushland Australian National University Bournda National Park City Renewal Authority Area Clyde Cameron Reserve Commonwealth & Kings Parks David Winterbottom Park Eurobodalla National Park Genoplesium plumosum target area Genoplesium superbum target area Genoplesium vernale target area Goulburn Mulwaree Council Goulburn Wetlands Griffith Woodland Haig Park Hughes Garran Woodland Isaacs Ridge and Nearby Isaacs Ridge Offset Area Lake Burley Griffin West MichaelBedingfied's Home Garden Mittagong Mongarlowe River Morton National Park Mount Ainslie to Black Mountain Mount Mugga Mugga Namadgi National Park Point Hut Pond Red Hill Nature Reserve Red Hill to Yarralumla Creek Stirling Park Sullivans Creek, Turner Tuggeranong Hill Wadbilliga National Park Wingecarribee Local Government Area WodongaPlaces
Mount Clear, ACT Narellan, NSW Red Hill, ACT Tennent, ACT Tomboye, NSW Wodonga, VIC