Rockland hammocks form on regions of rockland where a lack of fire has allowed hardwood trees to become dominant, nearly all of which are tropical in origin.[29] Natural firebreaks include exposed limestone cliffs and solution sinkholes.[30] Canopy species include gumbo-limbo (Bursera simaruba), paradise tree (Simarouba glauca), pigeonplum (Coccoloba diversifolia), Florida strangler fig (Ficus aurea), false mastic (Sideroxylon foetidissimum), willow bustic (Dipholis salicifolia), short-leaf fig (Ficus citrifolia), false tamarind (Lysiloma latisiliquum), West Indian mahogany (Swietenia mahagoni), and pepperleaf sweetwood (Licaria triandra). Epiphytes that grow in the canopy include Spanish moss (Tillandsia usneoides) and ball moss (T. recurvata). Plants such as black ironwood (Krugiodendron ferreum), inkwood (Exothea paniculata), lancewood (Damburneya coriacea), marlberry (Ardisia escallonoides), poisonwood (Metopium toxiferum), satinleaf (Chrysophyllum oliviforme), white stopper (Eugenia axillaris), shiny oysterwood (Gymnanthes lucida), wild coffee (Psychotria nervosa), shortleaf wild coffee (Psychotria tenuifolia), and pale lidflower (Calyptranthes pallens) grow in the understory. Southern live oak (Quercus virginiana), a temperate species, can be found on hammock margins.[29]