alien beach Carpobrotus edulis coast dune ecology flora flowers habitat hottentot fig ice plant introduction invasive natural nature pink plant sand soft Spain summer wild Aizoaceae angular-pigface Cape-fig carpobrotus-glaucescens coastal creeping-succulent daisy-like-flowers drought-resistant dune-stabilizer edible fire-resistant fleshy flower food groundcover Hottentot-plant ice-plant medicinal nutritional open perennials pigface pink-purple plant-mat prostrate salt-substitute salt-tolerant sand-dunes sand-stabilizer smooth-leaves sour-fig strand-ivy succulent sunlight sunshine thick triangular-leaves yellow all-weather-space Apocynaceae bark caudex caudiciform-plant conservatory display displayed distinctive dome exotics fat-twisted-roots flower-dome fockea-edulis gardens Gardens-by-the-Bay glasshouse gnarled greenhouse grotesque ground-level horticultural horticulture Hottentot-bread indoors plants semi-deciduous shape shaped shapes Singapore South-Africa-native surface surfaces texture textures tree trunk unusual utilitarian vegetation vine-branches bee bees insect insects