Chelsea Physic Garden Florilegium Society about the Florilegium Society at the Chelsea Physic garden.
ASBA the website of the American Society of Botanical Artists, who do a tremendous job raising public awareness of botanical art in the USA.
RHS this link is to the page on the Royal Horticultural Society website about exhibiting botanical artwork at their shows. Their picture committee sets the standard for quality in the botanical art world and the art exhibitions are a good place to begin if you want to start a botanical art collection, as prices are generally very reasonable and the artist is often there to answer any questions you might have about their work.
Katherine Tyrrell has written a blog with Ten Top Tips on winning an RHS Gold medal for Botanical Art which is an interesting read, and she also interviews Gold medal winning artists.
The Hunt Institute for Botanical Documentation hold an exhibition every three years of the best in contemporary botanical art. "Collectively, the 14 International catalogues include 1,129 artists and are the most comprehensive record available of contemporary botanical artists and illustrators."
SBA the annual Society of Botanical Artists exhibition, held in London, is well worth visiting to see the work of a broad range of botanical artists mainly from the UK.
Institute for Analytical Plant Illustration (IAPI) encourages the scientific illustration of flowering and non-flowering plants and communication of the diversity and intricacy of plant structures not necessarily visible to the naked eye.
Local Groups in the UK
There are many local botanical art groups in the UK either open to everyone or with some selection criteria - some just meet to paint, others have a programme of invited speakers/teachers/demonstrators.
Bath Society of Botanical Artists
Birmingham Society of Botanical Artists
Bristol and North Somerset Botanical Painting Society
The Eden Project Florilegium Society
Edinburgh Society of Botanical Artists
Frome Botanical Artists
Gloucestershire Society of Botanical Illustration
The Hampton Court Palace Florilegium Society
Horncastle Botanical Painters
ICENI Botanical Artists
Independent Botanical Illustration Society (Rotheram)
Leicester Floral Artists Society
Leicestershire Society of Botanical Illustrators
Mercia Botanical Artists Society
Botanical Artists of Ness Gardens
The Northamptonshire Botanical Artists Society
The Northern Society for Botanical Art
Nymans Garden Florilegium Society
Scottish Society of Botanical Artists
The Florilegium Society at Sheffield Botanical Gardens
The South West Society of Botanical Artists
Botanical Art Society of Sussex
Ventnor Botanical Artists
It is possible to get grants for illustrating particular projects and the UK National Lottery is a good place to start. You do need to fulfil certain criteria, but it can be a good way to pay for the costs of hanging an exhibition, raising awareness of your group, and getting some extra tuition and advice. One group received £3950 from the lottery for a Study of the Vascular Plants of Anston Stones Woods.