A new cultivar of oak leaf hydrangea resulting from a cross between 'Snow Queen' and 'Pee Wee'. The cultivar's claim to fame is its compact size maturing to only 3-4 ft tall and wide, ruby-red mature flowers, mahogany red fall foliage, and exfoliating bark. The particularly large panicles of flowers start white, but as the summer progresses, the color turns red, thus the name. 'Ruby Slippers' was introduced into the trade in 2010 by the U.S. National Arboretum.  Hardy to zone 5. This is a compact hydrangea, particularly suited for smaller landscapes or mass planting, also works well planted as a hedge.