Rhododendron, Genus, 'Johanna', Cultivar,
- Genus
- Cultivar
Johanna Azalea
Overview
Rhododendron 'Johanna' is an evergreen azalea of the Kaempferi group, forming a low, spreading mound 2-3 feet (60-90 cm) tall and 3-4 feet (90-120 cm) wide. Deep red single flowers about 1.5-2 inches (4-5 cm) across open in a single mid-spring flush from April to May. The glossy dark green leaves are 1-1.5 inches (2.5-4 cm) long and turn deep red-purple through winter, returning to green in spring. Hardy in USDA zones 6 to 9, it blooms only in spring and sets buds the previous summer, so a hard late frost reduces the display. Acidic, well-drained soil between pH 4.5 and 6.0 is required; foliage yellows with interveinal chlorosis at higher pH. All parts contain grayanotoxins toxic to pets and humans if eaten. It flowers most heavily in part sun with 4-6 hours of direct light.
Native Range
This azalea is a hybrid of garden origin and does not occur in the wild. Its parentage traces to evergreen azalea species native to East Asia, chiefly Japan and southern China.Suggested Uses
Used as a low edging, groundcover-scale massing, or front-of-border filler, spaced 3-4 feet (90-120 cm) apart. The spreading habit suits slopes and the fronts of shrub beds.How to Identify
Appearance
Size & Dimensions
Height2' - 3'
Width/Spread3' - 4'
Bloom Information
Blooms once in mid-spring, from April to May, in a single flush lasting about three weeks. Flower buds set the previous summer, so a hard late frost can reduce the display. Plants do not rebloom later in the season.
Detailed Descriptions
Foliage Description
Dark greenGrowing Conditions
Sun Requirements
Requires 4-6 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grows in part sun and flowers most heavily with 4-6 hours of direct light, with bloom thinning in deep shade. Requires acidic soil between pH 4.5 and 6.0 that drains freely while holding even moisture around its shallow, fibrous roots. Water deeply through the first two growing seasons and during summer dry spells. A 2-3 inch (5-7.5 cm) layer of pine bark or pine straw mulch conserves moisture and maintains soil acidity. Where soil pH rises above 6.0, leaves show interveinal yellowing that calls for an acidifying amendment. Lace bugs and spider mites can stipple foliage in hot, exposed positions.Pruning
Prune within three weeks after the spring flush, before next year's flower buds form. Light shaping maintains the spreading outline, while hard cuts reduce the following spring's bloom. Established plants tolerate cutting back by up to one-third to renew density.Pruning Schedule
Prune: May–June
late spring
Container Growing
Suitable for container growing
Minimum container size: 5 gallons
