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A small rosette species native to the semi-arid shrublands of South Africa's Eastern Cape Province. True to its Japanese common name Shizukuishi (雫石), meaning "dewdrop stone," the leaf tips swell into rounded globes and the transparent "windows" spread generously across each leaf. Under its Japanese trade name Obtusa, the plant has long been a staple introduction to succulent and Haworthia cultivation. POWO currently treats Haworthia cymbiformis var. obtusa (Haw.) Baker as the accepted name, but H. obtusa Haw. (1825) is so firmly established in Japanese horticultural trade that this site uses it as primary with the POWO synonym noted — the same approach taken with Pachypodium gracilius. Numerous selected cultivars such as OB-1 and Dodson Obtusa circulate in commerce; this page describes the straight species.
Native climate
Rainfall is spread fairly evenly across the year. Overall mild, with a wide temperature range.
* Accurate distribution data is scarce for this species, so these values are taken from the climate near the approximate center of its native range instead.
Sources: climate & elevation WorldClim 2.1 (1970–2000) · occurrences GBIF · native range POWO · current weather Open-Meteo
Care
Light & Placement
In its natural habitat the plant grows semi-buried at the base of shrubs or in the shelter of rocks, where strong direct sun is the exception rather than the norm. During Japan's midsummer heat above 30 °C, growth slows and a combination of intense light and high temperature causes the leaves to turn reddish-brown and the windows to cloud over. During the spring and autumn growing seasons (March–May, September–November), about 50 % shade cloth allows soft, diffuse light to reach the plant; in midsummer, shade is increased further or the plant is moved to a bright, shaded spot. Indoors, an east- or south-east-facing window filtered through a sheer curtain works well. When grown outdoors, positioning on a raised bench with good airflow — rather than directly on the ground — helps keep conditions stable. A bright indoor windowsill without supplemental heat is sufficient through winter.
Watering
During the spring and autumn growing seasons, water thoroughly once the growing medium has dried out, then repeat as the surface dries again. Through the semi-dormant periods of high summer and midwinter, watering is reduced to a light moistening once or twice a month.
Substrate
The balance between drainage and moisture retention matters. A base mix of fine-grain akadama : fine-grain kanuma : pumice at 4 : 3 : 3 works well; because the roots are fine, skewing slightly toward smaller particle sizes is worthwhile.
Fertilizer & Supplements
During the growing season, a liquid fertiliser diluted to more than double the manufacturer's recommended concentration, applied once or twice a month, is sufficient. Heavy feeding causes the leaves to elongate and the clarity of the windows to diminish.
Temperature & Overwintering
The preferred growing range is 15–28 °C, with a minimum of approximately 3 °C. When the medium is dry the plant can tolerate near-freezing temperatures, but wet soil combined with cold damages the roots. Through midwinter, dry dormancy on a bright indoor windowsill keeps the plant in good condition.
Starting from Seed
Where to source seeds
Pre-sowing treatment
Seeds are soaked for half a day in a solution combining a fungicide (such as Benlate or Daconil) with a biostimulant supplement (such as Menedael). Viability varies with storage conditions, so choose a supplier who can confirm the harvest year and sow promptly after acquisition.
Substrate
Fine-grain akadama : fine-grain kanuma : vermiculite at 1 : 1 : 1, sterilised in a microwave or with boiling water before use. A level, smooth surface helps very small seeds settle evenly.
Sowing method
Surface sowing with little or no covering of the seeds is standard. Because the seeds are fine and scatter easily, placing each one individually with the moistened tip of a toothpick makes positioning manageable. Seeds should be spaced at least 5 mm apart.
Light & temperature
A stable 22–28 °C under bright shade. Germination typically occurs within 7–21 days. Seeds stored under appropriate conditions germinate reliably.
Watering
Shallow tray-watering (capillary irrigation) with 1–2 cm of water in the tray. For the first three to four weeks, preventing the medium from drying out completely takes priority; once germination is underway, the water level is gradually reduced.
Fertilizer
No fertiliser is needed immediately after germination. Once the first true leaves are developing, a liquid fertiliser diluted to more than double the manufacturer's recommended concentration, applied once or twice a month, is ample.
After Germination to First Repotting
Germination through true leaves (up to 2 months)
Continue tray-watering and keep the seedlings in bright shade.
Weaning off bottom watering (months 2–4)
Gradually lower the water level in the tray, transitioning to bottom-up watering.
First repotting (year 1–2)
Once the root ball fills the container, transplant into a fine-particle growing medium.
Common Problems
Mold & damping-off
- Cause: Pathogenic organisms in the growing medium, excess moisture, insufficient airflow
- Prevention: Sterilise the medium before use, refresh the tray water regularly, and ensure circulation with a small fan
Leaf scorch & clouded windows
- Cause: Excessive light, coinciding with high summer temperatures, or abrupt changes in environment
- Prevention: Approximately 50 % shade cloth in spring and autumn; move to bright shade in midsummer; allow at least a week for the plant to adjust to any environmental change
Seeds fail to germinate
- Cause: Seed viability past its prime, insufficient temperature
- Prevention: Choose suppliers who can confirm the harvest year; use a heat mat to maintain a steady 22–28 °C
Seedlings don't match the named selection
- Cause: Most Obtusa plants in cultivation are selected clones, and seedlings grown from open-pollinated species seed rarely reproduce the same traits
- Prevention: For a specific selection (OB-1, Dodson Obtusa, etc.), offsets or leaf-propagated plants are the reliable route
Notes
No toxicity has been reported at the genus level.