Wild Thyme
Rhododendron serpyllifolium
Ericaceae · broadleaf deciduous shrub · introduced
Last updated
A deciduous azalea native to the southern half of Honshu, Shikoku, and Kyushu, Japan, reaching 3 to 4 feet. Pale rose or white flowers. Named for the tiny thyme-like leaves, among the smallest of any azalea species.
Hardy in Zone 6a-8b. The miniature foliage gives this species a fine-textured appearance unlike any other azalea. Acidic, well-drained soil. Twenty-one diseases and 15 pests documented at the genus level. All parts contain grayanotoxins and are toxic if ingested.
Plant Profile
Size & Form
Height
3–4 ft
Site Requirements
Hardiness
Zones 6a–8b
Ornamental Interest
Origin
Japan, southern half of Honshu and in Skikoku and Kyushu
Watch for this season
Root Colonization (Spring–Fall)
Gall Development & Sporulation
Powdery MildewHigh
Active Conidial Spread
RustHigh
Uredinial Stage (Summer)
+ 13 more — see full disease and pest lists below
Diseases: Regionally Documented (21)
Root Rot (Phytophthora spp.) Multiple obligate biotrophic fungi (Erysiphales: Erysipha... Powdery Mildew Ovulinia azaleae Ovulinia Petal Blight Lime-induced Chlorosis Symptom category — not a single disease Leaf Spot Exobasidium vaccinii Leaf and Flower Gall Cylindrocladium scoparium Cylindrocladium Blight and Root Rot Botrytis Petal Blight Multiple soilborne and waterborne pathogens cause cutting... Cutting Rots Leaf Burn Ramorum Blight (Sudden Oak Death) Botryosphaeria dothidea Botryosphaeria Dieback Seifertia azaleae Bud Blight Rhododendron necrotic ringspot virus Necrotic Ringspot Multiple genera (Melampsoridium, Thekopsora, Naohidemyces... Rust Taphrina wiesneri Witches' Broom Armillaria spp. — primarily A Armillaria Root Rot Pestalotiopsis sydowiana Gray Blight Physiological leaf spot Phytophthora Blight Tylenchorhynchus claytoni Nematode, Stunt
Pests: Regionally Documented (15)
Tetranychidae Spider mite Otiorhynchus spp. Root weevil Choristoneura rosaceana Obliquebanded Leafroller Caloptilia azaleella Azalea leafminer Stephanitis pyrioides Azalea Lace Bug Acanthococcus azaleae Azalea bark scale Aphidoidea Aphid Lepidoptera Caterpillars Parthenolecanium spp. Lecanium scale Stephanitis rhododendri Rhododendron lace bug Dialeurodes chittendeni Rhododendron whitefly Nematus lipovskyi Azalea sawfly Cacoecimorpha pronubana Carnation tortrix Icerya purchasi Cottony cushion scale Coleotechnites huntella Rhododendron bud moth
Data Maturity Structured Multiple sources. Expert review underway.