 Banksia violacea is one of a small number of Banksia species that has both lignotuberous and non @-@ lignotuberous populations . In both cases , plants are adapted to release their aerial seed bank following a <unk> , ensuring seedlings are established on clear and relatively fertile ground ; however the possession of a lignotuber makes plants much less reliant on fire regime for population maintenance and regeneration , as maternal plants are not killed by <unk> , but <unk> from below ground level . <unk> plants generally occur among the north @-@ eastern populations , in the vicinity of <unk> . An investigation into the <unk> of these plants failed to find any <unk> , climatic or other environmental factors associated with the possession of a lignotuber . 
