Hibiscus syriacus ‘Greba’
Hibiscus syriacus ‘Greba’, marketed under the name Blue Angel™ Shrub Althea, is a delightful Hibiscus syriacus developed by Dr. Sam McFadden from crosses between ‘Bluebird’ and ‘Diane’. Hibiscus syriacus ‘Greba’ is a vigorous growing shrub to small tree with an extended blooming season featuring beautiful single blue broadly trumpet-shaped flowers. Hibiscus syriacus ‘Grewa’ is another hybrid cultivar of Dr. McFadden’s, which is a result of a cross between Hibiscus rosa-sinensis x Hibsicus syriacus ‘Diane’, that provides similar garden characteristics but a somewhat larger final size and numerous clean white flowers. Hibiscus syriacus ‘Grewa’ is marketed under the name White Angel™ Shrub Althea. Shrub Althea is at times known as Rose-of-Sharon and these shrubs have long been regional gardening favorites. These two cultivars offer tough versatile plants with reliable attractive warm season flowers.
Exposure: Best flowering is in full sun or light afternoon shade. Shady locations tend to reduce flower production.
Size: Height — This cultivar is somewhat smaller than the typical species type, maturing at 6 to 8 ft after several years. Plants eventually form upright oval to vase-shaped habits with a spread equal to or often less than their height.
Plant type: Erect woody deciduous shrub or small tree.
Planting time: Bare root plants in early winter, container-grown or balled-and-burlapped plants year-round.
Soil type: Well drained soils are needed. Plants are usually well adapted to a range of soil pH, but may occasionally require iron chelate on very high pH soils; plants are favorably responsive to good fertility, but can persist in low to moderate fertility soils. These shrubs are moderately drought tolerant once established.
Suggested uses: Blue Angel™ can be incorporated in the landscape as a general-purpose deciduous shrub, warm season accent, limbed up as a small tree, or grown in large landscape containers. Flowers provide ecosystem services as pollinator and hummingbird attractants and are sometimes employed as cut flowers for floral arrangements. These shrubs are useful in USDA hardiness zones 5 to 8 (9); insufficient winter chilling can sometimes reduce or delay budbreak in warmer parts of zone 9.
Special notes: Not to be confused with Hibiscus x moscheutos ‘Blue Angel’ which is a herbaceous perennial, not a woody shrub; avoid soils with cotton root rot; light aphid infestations can often be controlled by a removal with a strong stream of water.