Rhododendron 'Robles' ENCORE AUTUMN LILAC
Common Name: evergreen azalea 
Type: Broadleaf evergreen
Family: Ericaceae
Zone: 7 to 9
Height: 2.00 to 3.00 feet
Spread: 2.00 to 3.00 feet
Bloom Description: Lilac with purple freckles
Sun: Part shade
Water: Medium
Maintenance: Medium
Suggested Use: Hedge
Flower: Showy
Leaf: Evergreen
Other: Winter Interest
Tolerate: Rabbit


Best grown in acidic, organically rich, humusy, medium moisture, moisture-retentive but well-drained soils in part shade. Prefers a sun dappled or high open shade. Morning sun with afternoon shade is also acceptable. Tolerates a fair amount of sun in cool northern summers, but leaves may scorch in hot afternoon sun in the St. Louis area. Plant in a location protected from strong winds. Plants perform well on north or east facing slopes. Do not site plants within or near the drip line of trees in the walnut family (most rhododendrons/azaleas are sensitive to toxic juglones produced by roots of walnuts, butternuts, pecans and hickories). Good soil drainage is essential (plants do not like “wet feet”). Poor drainage inevitably leads to root rot, therefore raised beds/plantings should be considered in heavy clay soils such as those present in much of the St. Louis area. Shallow, fibrous root systems (do not cultivate around plants) will benefit greatly from a mulch (e.g., wood chips, bark or pine needles) to help retain moisture and stabilize soil temperatures. Roots must never be allowed to dry out. Acidify soils as needed (plants generally like soil pH in the range of 5.0 to 5.5). Add sulfur or iron sulfate to soils to lower the pH. Add limestone or lime to soils to raise the pH. Clip off spent flower clusters immediately after bloom as practicable.

'Robles' is Winter hardy to USDA Zone 7. Plant in protected locations in USDA Zone 6.

Noteworthy Characteristics

Rhododendron is a genus of 500 to 900 species and includes both of what we commonly call rhododendrons and azaleas. Most are evergreen but some are deciduous. They originate mostly from the Northern Hemisphere with high concentrations in western China, the Himalayas and Myanmar (Burma). They are grown for their showy spring flowers and in the case of evergreen types for their attractive winter foliage. True rhododendrons have 10 stamens in a flower and azaleas have only 5. Much hybridization has resulted in a great number of hybrid cultivars. Of note to gardeners in cool temperate areas are the large and small leaved evergreen rhododendrons and the evergreen and deciduous azaleas.

Evergreen azaleas develop as multi-stemmed plants from the ground and usually grow 3-5 feet tall. They retain their leaves throughout the year and are not as winter hardy as the deciduous azaleas. In cold winters flower buds may be frozen resulting in reduced or no flowering and foliage may winter burn (turn brown and be killed). Color range is mostly from white to pink, red, lavender and purple.

Genus name comes from the Greek words rhodo meaning rose and dendron meaning tree. Transferred from the Greek name for Nerium oleander.

'Robles', commonly sold under the trade name of AUTUMN LILAC, is a compact evergreen azalea (Encore Series) that typically matures over time in an upright, dense, rounded form to 3' tall and as wide. Single, open, funnel-shaped, lilac flowers (to 3 1/4" diameter) with darker purple-violet freckles typically bloom for 2-3 weeks in early-midseason (April-May), and, with a somewhat sporadic additional bloom, from early July to frost. Elliptic, pubescent, dull green leaves (to 2" long) are evergreen. AUTUMN LILAC is the result of a cross between Rhododendron 'Watchet' (female parent) and Rhododendron 'Conleb' AUTUMN EMBERS (male parent) which occurred in April of 1996 under a controlled breeding program conducted in Independence, Louisiana by Robert Edward Lee. AUTUMN LILAC is reportedly very similar in characteristics and appearance to AUTUMN EMBERS except for flower color (lilac for the former and orange-red for the latter). Encore Series azaleas (29 different varieties as of 2013) are all repeat bloomers. The quality and quantity of mid-summer to fall bloom depends in part on the climate, location and correct sun/shade balance of the plant. The trademark name of each azalea in the Encore Series begins with the word AUTUMN in obvious reference to the fall bloom of each plant. U.S. Plant Patent PP22,762 was issued for AUTUMN LILAC on May 29, 2012.


Rhododendrons and azaleas are susceptible to many insect and disease problems. Insect pests include aphids, borers, lacebugs, caterpillars, leafhoppers, mealybugs, nematodes, scale, thrips and whitefly. Mites may also appear. Disease pests include blights, canker, crown rot, leaf gall, root rot, leaf spot, rust and powdery mildew. Chlorosis (leaves turn yellow) often indicates an iron deficiency in the soil that is often caused when the soil pH becomes too high. A healthy plant in the proper environment with proper care should have limited problems, however.

Garden Uses

Mass, group or specimen. Shrub borders, mixed borders, woodland gardens and shade gardens. Also effective in foundation plantings or as a hedge. Woodland margins.