Hibiscus Syriacus ‘Helene’ and ‘Diana’

Two Outstanding National Arboretum Introductions

Three different plants are commonly called Hibiscus – the tropical houseplant, the perennial rose mallow with dinner plate-sized flowers that dies to the ground each fall and the Rose-of-Sharon or shrub Althea. Rose-of-Sharons are easy-to-grow, tall flowering shrubs that will bring amazing color to your garden throughout the summer. Native to much of Asia, they thrive in the heat of summer. The USDA has introduced four cultivars of Rose-of-Sharon over the years. Two are unimpressive; two are outstanding – in our opinion the two best Rose-of-Sharon in existence: Hibiscus syriacus ‘Helene’ and Hibiscus syriacus ‘Diana.’

‘Helene’ produces gorgeous, pure white flowers with prominent ruby red throats. ‘Diana’ produces waxy, pure white flowers.

Both are a vase shaped, multi-stemmed deciduous shrubs with a vigorous upright growth habit. They mature to a height of 8-12 feet by 6 feet wide and can be trained as a large shrub or a small tree. Both varieties produce flowers with broad overlapping petals of an unusually heavy waxy substance. Both are also virtually sterile so they produce no unwanted seedlings, which are the bane of the common Rose-of-Sharon. Sterility also causes these varieties to be unusually long blooming as they produce more flowers in a futile attempt to set seeds. The beautiful flowers are enhanced by the deep green glossy foliage – deeper green than I have seen on any other Rose-of-Sharon.

Either variety can be trained as a small tree or planted in masses as a screen. ‘Diana’ and ‘Helene’ are particularly attractive planted around a deck, patio or swimming pool – either in the ground or in pots.

Planting and Care

  • Plant in full sun; will grow and bloom in moderate shade.
  • Tolerant of a broad range of soil moisture conditions from moist to, once established, quite dry. Will not tolerate soggy soils.
  • Use a handful of Plant-Tone fertilizer in early spring.
  • If necessary, prune in spring before the leaves appear.
  • Rated as deer resistant.
  • Hardy in Zones 5 – 9.