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During summer 2001 a vegetation survey was undertaken of Poole Harbour Special Protection Area. The survey involved mapping the lower and mid-upper salt-marsh zones and any habitats listed on Annexe I of the European Union Habitats Directive. Locations of rare and uncommon plant species were also mapped. Salt-marsh and associated plant communities were described along with transitional vegetation at the back of the salt-marsh, and, where, possible, assigned to their appropriate National Vegetation Classification (NVC) community or sub-community.

As a result of the survey seven Annexe I habitats were mapped. A total of thirty-nine NVC communities and sub-communities were found to be present, twenty-two from salt-marshes, eight from sand dune and shingle habitats, seven brackish swamps and two brackish grasslands. Several types of vegetation did not fit easily within the NVC and are described in detail. The transitional vegetation between salt-marsh and mire is of particular interest and is possibly unique to the harbour.

There is a total of 440 ha of salt-marsh within the harbour, a decrease of some 190 ha since the last survey in 1985, this is largely due to the continued erosion of the Spartina beds. By contrast reedbeds increased by some 32 ha during the same time period.

The flora of the harbour is largely restricted to halophytic species, with the richest flora found in the upper salt-marsh particularly where there is some freshwater seepage. One hundred and forty species were recorded, including two Red Data Data book and six Nationally Scarce species. A new population of One-flowered Glasswort was discovered, but the rare Dwarf Spike-rush was not refound.