The only cycad native to Japan, Cycas revoluta Thunb. was described by Carl Peter Thunberg in 1782 from material gathered on his Japanese stay; its Japanese name sotetsu (蘇鉄) has been recorded since antiquity. The species ranges from southern Kyushu through the Ryukyu Islands to coastal Fujian in southern China and eastern Taiwan, where it grows on warm-temperate to subtropical rocky slopes. Plants reach 1–7 m, with a thick grey caudex and a rosette of 50–150 cm pinnate fronds, and have long been planted around shrines, temples, and sacred sites such as Sefa-Utaki on Okinawa. It is the hardiest cycad in cultivation and can overwinter outdoors south of the Kantō region. Listed on CITES Appendix II and assessed as Least Concern by the IUCN; every part of the plant contains the potent toxin cycasin, and ingestion can cause severe liver damage.
Native climate
Rainfall is spread fairly evenly across the year. Overall a mild climate.
A broad-scale picture of the native range. Real growing spots — rock crevices, fog belts — can be milder.
Sources: climate & elevation WorldClim 2.1 (1970–2000) · occurrences GBIF · native range POWO
Care
Light & Placement
A full-sun plant from subtropical coastal rock, in active growth it wants as much direct sun as possible — strong light keeps the leaves short and stiff and tightens the deep green colour, while shaded plants etiolate and yellow. Keep shading under 20–30 percent even in Japan's midsummer, and raise pots off the ground for airflow rather than letting them sit on bare earth. Planted in the ground in southern Kantō or further south, it overwinters outdoors without protection. Potted specimens are best moved to a bright eave or indoor window out of rain in winter.
Watering
Water deeply once the surface has dried in active growth, and never leave water in the saucer. In winter, taper to once or twice a month. Cold plus wet soil is the main rot trigger.
Substrate
Drainage first, inorganic-led: Akadama : Kanuma : pumice = 3:3:4. Use a deep pot so the taproot can run straight down — this stabilises the plant.
Fertilizer & Supplements
A diluted liquid feed once a month in active growth, or a small pinch of slow-release at repotting. Growth is slow and overfeeding does not speed it — it only stretches the fronds.
Temperature & Overwintering
Optimal 22–32°C, minimum around −5°C. This is the hardiest cycad on the market, and south of Kantō it overwinters outdoors. Dry plants are reported to take brief dips to −8 to −10°C. Cold and wet soil together are fatal.
Starting from Seed
Where to source seeds
Pre-sowing treatment
The red fleshy seed coat (sarcotesta) invites rot — soak briefly to soften and remove it before sowing. Soak seeds for about half a day (overnight) in a mix of a registered seed-treatment fungicide (Benlate or Daconil) and a plant tonic (Menedael; outside Japan, SUPERthrive or a chelated iron / seaweed extract works similarly), each diluted per label. Floaters tend to be old or infertile. Germination requires steady warmth of 25–32°C.
Substrate
Lean toward straight inorganic — pumice fines as the base, or fine Akadama with pumice at 1:2. Use a deep pot for the taproot and sterilise the mix with boiling water or a microwave pass beforehand.
Sowing method
Lay the seed on its side — orientating the seam vertically distorts the emerging root. Cover only thinly so the upper half of the seed remains visible.
Light & temperature
Bright shade at a steady 25–30°C; a heat mat stabilises the soil temperature. Germination is uneven, taking 1–3 months on average. Don't discard the tray after three quiet months.
Watering
Bottom-water with the level 1–2 cm up the pot, refreshing it often to keep rot risk down. Drop the level gradually once seedlings emerge.
Fertilizer
No feeding right after germination. Once the first pinnate leaf opens, give a heavily diluted liquid feed once a month — growth is slow, so do not push the dose.
From Germination to Repotting
Germination through true leaves
Cotyledon first, then a pinnate leaf.
Weaning off bottom watering
Phase out over two to three months.
First repotting
In year two or three, into a deep pot.
Common Pitfalls
Mold & damping-off
- Cause: residual sarcotesta, excess moisture, contamination
- Prevention: clean off the fleshy coat completely, sterilise the substrate, refresh bottom-water often, and run a circulation fan
Etiolation
- Cause: insufficient light
- Prevention: harden off into strong light right after germination — outdoor sun or high-output LEDs keep the rachis short and stiff
Seeds fail to germinate
- Cause: stale seed, insufficient warmth, giving up too early
- Prevention: source fresh seed, hold 25–30°C steady on a heat mat, and keep the tray for at least three to six months
Notes
CITES Appendix II — seed, seedlings, and mature plants all require permits for international trade. The seeds are highly toxic; keep them out of reach of children and pets.
