Source: Wikimedia Commons
Keisk's rhododendron
AdvancedRhododendron keiskei
An endemic Japanese dwarf rhododendron, unusual among Japanese azaleas for its cream to pale yellow flowers in April–May. It grows on rocky slopes and streamsides; the creeping dwarf Yakushima form is sold for shohin and rock gardens.
About
Rhododendron keiskei is an evergreen shrub endemic to Japan, found in Honshu west of Kanto, Shikoku and Kyushu north of Yakushima. It grows on rocky mountain slopes, cliffs and rocky stream banks, and despite its Japanese name ('shade azalea') it is botanically a scaly-leaved (lepidote) rhododendron. In April–May it bears 2–4 cream to pale yellow-green flowers 3–4 cm across at the shoot tips—a rare yellow among Japanese azaleas. The oblong leaves are 4–8 cm long; shoots, leaves and flowers carry glandular scales, and the leaf edges roll under when dry. It grows 1–2 m tall. On Yakushima a creeping dwarf form (var. ozawae) grows only about 30 cm in 10 years, with leaves 1.5–2.5 cm long, and is sold for shohin bonsai and rock gardens. Take care with var. hypoglaucum, whose leaf undersides are grey-white: it is a Nationally Rare Species under Japan's Species Conservation Act, and trading it is generally prohibited. It prefers humid conditions and is hard to keep long-term in dry urban settings.
Size of the Keisk's rhododendron
The Keisk's rhododendron grows to 1–2 m tall; the Yakushima dwarf form reaches about 30 cm in 10 years.
Basic Info
Origin
Endemic to Japan (Honshu west of Kanto, Shikoku, Kyushu to Yakushima)
Lifespan
Little data on lifespan
Size
1–2 m tall; the Yakushima dwarf form reaches about 30 cm in 10 years
Temperature
-5〜35℃
Watering & Fertilizer
Fertilizer (sparingly after flowering and in autumn)
Growing Tips
Light & placement
Grows in sun as well as shade but not in deep shade. Bright part shade out of hot afternoon sun is easiest
Watering
Likes moisture and dislikes drought. Water well as the surface starts to dry and mist in summer; leaf edges roll under when too dry
Temperature & overwintering
The typical form is rated to about −18°C (0°F) and the Yakushima dwarf to about −23°C (−10°F); summer heat and dryness are the harder part
Soil & repotting
As for azaleas, use acidic, free-draining, airy soil such as kanuma. Repot after flowering
Fertilizer
Slow-growing, so feed lightly—a little after flowering and in autumn
Pruning & styling
Prune right after flowering. Growth is slow, so little cutting is needed; keep its natural multi-stemmed habit
Pests & cautions
Var. hypoglaucum (grey-white leaf undersides) is a protected Nationally Rare Species and may not be traded—avoid plants you cannot identify. Buy nursery-grown plants, never wild-dug ones
Keisk's rhododendron FAQ
QWhat is the growing difficulty level for Keisk's rhododendron?
Advanced. A variety suitable for advanced growers. Requires advanced cultivation techniques and specialized equipment, with careful environmental adjustments needed.
QHow large does Keisk's rhododendron get?
The mature size of Keisk's rhododendron is 1–2 m tall; the Yakushima dwarf form reaches about 30 cm in 10 years. This may vary slightly depending on cultivation environment and individual differences.
QHow should I water and fertilize Keisk's rhododendron?
Keisk's rhododendron: watering & fertilizer — Fertilizer (sparingly after flowering and in autumn). Aim for appropriate frequency and amount.
QWhat is the typical price for Keisk's rhododendron?
The price of Keisk's rhododendron varies significantly by variety, characteristics, size, and lineage. Please check GrowerDirect's price guide for the latest market information.
Last updated: September 23, 2026
References & Sources
Edited & verified by: GrowerDirect Editorial Team
The classifications, regulations, and growing data on this page are created and verified based on the primary information database below.
Primary sources
- Species+ (CITES listing search)
- Ministry of the Environment: Nationally Rare Species list (R. keiskei var. hypoglaucum)
- Wikipedia (Japanese): Rhododendron keiskei
- Uekipedia: Rhododendron keiskei
- Oregon State Univ. Landscape Plants: Rhododendron keiskei
- Kimi's mini bonsai days: Satsuki care (soil for azaleas)
- GBIF
- GBIF: Rhododendron keiskei var. ozawae
Taxonomy & Authority
Accepted name: Rhododendron keiskei Miq.
Synonyms: Azalea keiskei (Miq.) Kuntze, Rhododendron jodogawa Hassk., Rhododendron laticostum Ingram
Authority databases: GBIF · GBIF · GBIF: Rhododendron keiskei var. ozawae
Nomenclature follows global taxonomic authority databases.
Regulations & Conservation Status
The species is neither CITES-listed nor restricted for domestic sale. However, var. hypoglaucum is a Nationally Rare Species under Japan's Act on Conservation of Endangered Species (designated May 2012); selling, giving and displaying or advertising it for sale are generally prohibited. Do not list or buy plants with grey-white leaf undersides, and choose cultivated rather than wild-collected plants.
Sources: Species+ (CITES listing search) / Ministry of the Environment: Nationally Rare Species list (R. keiskei var. hypoglaucum)
Regulations may change. Always verify the latest information with the relevant authorities.
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