alien araceae foreign garden escape green invader Lysichiton americanus nature plant skunk cabbage spadix spathe Swamp lantern yellow black brightly-coloured carpeting-plants clump-forming clumps colors colours common daisy-like drought-tolerant environmental-weed flower flowers garden flowers garden-escape gazania gazanias golden hardy introduced-species invasive lance-shaped leaves low-growing orange perennial plants prolific rapid-spreader resilient roadside-weeds South-African streaked tough vivid water-wise weed widespread wind-blown seeds brightly coloured carpeting plants environmental weed introduced species rapid spreader roadside weeds South African color coloration colored colorful colour coloured colourful garden-flowers lance-shaped-leaves wind-blown-seeds appearance