Spider plants have long narrow leaves that are 20 â `` 40 cm ( 8 â `` 15 in ) long and 5 â `` 20 mm ( 0.2 â `` 0.8 in ) broad . They grow from a central rosette . Spider plants have long narrow leaves that are 20 â `` 40 cm ( 8 â `` 15 in ) long and 5 â `` 20 mm ( 0.2 â `` 0.8 in ) broad , growing from a central rosette .