Hosta Knockout will grow into a medium-sized Hosta, reaching 30cm-40cm in height with a spread of about 50cm at maturity. The growth rate is medium to slow. The leaves are broadly ovate with a thick texture. Due to its wide variegated white margin, the leaves may be thinner and can sometimes suffer small tears along the edges. The grey-green leaves have a yellow margin that changes to creamy, which may turn brown in extremely hot summers. It produces near-white flowers on scapes that are 60cm tall from late June to July. This cultivar holds up well against slugs and is tolerant of sun exposure.