Madelon Gilligan of New Zealand registered this upright growing, open-pollinated seedling of H. 'Lemon Honey' in 2015. 'Lemon Slice' is a small size plant about 9 inches high by 20 inches wide at maturity. It has yellow leaves which are slightly rippled, broadly ovate, slightly wavy and dull on top. Pale lavender, tubular flowers bloom from June into July. It sets seeds but their viability was not known at the time of registration.