Swamp Banksia grows in and around wetlands, lakes and rivers throughout the Swan Coastal Plain and the Darling Range. It’s common at Lake Gwelup. Some have been planted in revegetation projects eg. along the boardwalk. Others are original vegetation, like this enormous tree on the east side of the lake which is countless years old.
When not in flower, an easy feature to identify Swamp Banksia is the narrow leaves which are green on top and white underneath.
“As gusts of wind pass through a swamp banksia its leaves will often turn over, and its foliage will appear to change colour from green to white.” 
Scientific name Banksia littoralis
Common name Swamp Banksia
Flower March – August
Seed pod fruit forms woody cone
Among the trees at Lake Gwelup I can only find seed cones on the very old tree, despite the younger trees flowering every year. The height means I had difficulty taking photos. (I found this photo on Flickr.)
Associated wildlife Nectar available in winter is an important food source for birds. Larvae of a jewel beetle (Cyria vittigera) burrow in the trunk and the adult beetle eats the leaves. Weevil larvae burrow in the cone to eat the seeds. Banksia moth caterpillars (Danima banksiae) eat the leaves (and are amazing to see). The larvae of a gall wasp causes brown swellings on the leaves. 
Bark rough, grey
The trunk can grow huge like this tree at Lake Gwelup. Robert Powell believes they may live longer than other Perth banksias. 
Growth habit shrub or spreading tree up to 12m. Grows in or beside wetlands and watercourses.  After fire re-shoots from epicormic buds. 
Florabase record http://florabase.com/browse/profile/1830
- Powell, Robert (2009) Leaf and Branch: Trees and Tall Shrubs of Perth (2nd ed) Perth: DEC
- Barrett & Tay (2005) Perth Plants Perth: BGPA