have less than 30% of the cover of uninfested areas. Plant deaths in such large proportions can have a profound influence on the makeup of plant communities. For example, in southwestern Australia Banksia often occurs as an understorey to forests of jarrah (Eucalyptus marginata), another species highly vulnerable to dieback. Infestation kills both the jarrah overstorey and the original Banksia understorey, and over time these may be replaced by a more open woodland consisting of an overstorey of the resistant marri (Corymbia calophylla), and an understorey of the somewhat resistant Banksia sessilis (parrot bush). A number of species of Banksia are threatened by dieback. Nearly every known wild population of B. brownii shows some signs of dieback infection, which could possibly wipe it out within years. Other vulnerable species include B. cuneata, and B. verticillata. Dieback is notoriously difficult to treat, although there has been some success with phosphite and phosphorous acid, which are currently used to inoculate wild B. brownii populations. However this is not without potential problems as it alters the soil composition by adding phosphorus. Some evidence suggests that phosphorous acid may inhibit proteoid root formation. Because dieback thrives in moist soil conditions, it can be a severe problem for banksias that are watered, such as in the cut flower industry and urban gardens. Uses Gardening Most of species are shrubs, only few of them can be found as trees and they are very popular because of their size, the tallest species are: B. integrifolia having its subspecies B. integrifolia subsp. monticola notable for reaching the biggest size for the genus and it is the most frost tolerant in this genus, B. seminuda, B. littoralis, B. serrata; species that can grow as small trees or big shrubs: B. grandis, B. prionotes, B. marginata, B. coccinea, B. speciosa and B. menziesii. Due to their size these species are popularly planted in parks, gardens and streets, the remaining species in this genus are only shrubs. Banksias are popular garden plants in Australia because of their large, showy flower heads, and because the large amounts of nectar they produce attracts birds and small mammals. Popular garden species include B. spinulosa, B. ericifolia, B. aemula (Wallum Banksia ), B. serrata (Saw Banksia), Banksia media (Southern Plains Banksia) and the cultivar Banksia 'Giant Candles'. Banksia species are primarily propagated by seed in the home garden as cuttings can be difficult to strike.