Hibiscus, or rosemallow, is a large genus which includes more than 200 species of deciduous and evergreen shrubs and trees, as well as annual and perennial herbaceous plants. Almost all of them are native to tropical and subtropical regions throughout the world (including the popular houseplant – the Chinese hibiscus (Hibiscus rosa-sinensis)); hence only very few of the genus can be grown outside in temperate climate. The common garden hibiscus (Hibiscus syriacus) is the most widely grown hardy species.
Hardy does not always means really hardy… Garden hibiscus may succesfully grow here for many years if winters are not very cold, and die back to the ground in a heavy winter like we had this year. Anyway new shoots grow fast and start flowering in late summer. Young plants are more frost-sensitive. Hibiscus feel good during our cool summers, they can be container-grown, moving them inside for the winter. Heavy mulching helps roots to survive the winter.
The common garden hibiscus (Hybiscus syriacus) is native to China and Western Asia. This species of hibiscus is well-loved and widely grown in Europe. These are compact shrubs of variable height up to 2-4 m. Flowers, which are smaller than those of true chinese hibiscus, come in a variety of colours – ranging from white to lilac, often bicoloured, single or double.
Garden hibiscus are widely used as landscape shrubs or small tress. They thrive in sunny, well-lit and moist locations. During hot weather, they require copious watering and feeding in order to extend their flowering from mid-July up to the first frosts. They tolerate shady position, but the flower display will be less spectacular. However in sunny position they overflower very fast.
Propagation is from seed (species), or by green and semi-woody cuttings (cultivars). Seeds are sown in early spring after the cold germination treatment.
Common hibiscus are not particular about the soil (they do need a well-drained spot though), but they strongly prefer full or half full sun, growing spindly in shaded location. They dislike strong winds. They are drought-resistant, but produce exceptional quantities of flowers, when regularly watered and fertilised. During cold spring with recurrent frosts, the young shoots of hibiscus should be protected (but mostly they sprout quite late, after the spring frosts are passed).
Winter thaws can be lethal to rosemallows, if their roots remain waterlogged for some time, therefore a thick layer of draining material should be spread at the bottom of the planting hole when planting hibiscus is clay soils.
© Giedra Bartas, 2010