Liriope muscari 'Monroe White'  is a white-flowered monkey grass which begins blooming in mid August and is blooming now.  It gets about one foot tall and has evergreen dark green foliage.  It's a nice change from the typical purple-flowered Liriope.  I have both in our backyard with a section of white, then a section of purple, and ending with another section of white.  

Liriope muscari 'Monroe White'