Haworthia cooperi var. truncata: growing clear windows, not leaves
In this plant the leaf tip has been reduced to a translucent window that lets light into buried photosynthetic tissue. Everything about its care follows from that: it wants very little direct light, a great deal of humidity, and it will tell you immediately when the balance is wrong.
4,000–12,000 lux, and why the windows cloud
The window is clear only while the tissue underneath is unstressed. At 4,000–12,000 lux the leaf tips stay glass-clear with visible internal striping. Above 20,000 lux the cells beneath the window produce protective pigments and the tip goes milky, then opaque white, then brown. That damage does not reverse on the affected leaf.
The practical placement is a shaded shelf, an east window behind a sheer blind, or 60 cm beneath a low-output LED bar. If you are using a lux meter, aim for 6,000–9,000 lux and check it at the leaf tips, not at the pot rim.
Water and air humidity pull in opposite directions
H. cooperi has shallow, fleshy roots and no water-storage stem, so total drought is more dangerous for it than for a Haworthiopsis. An 8 cm rosette in a 9 cm pot wants water every 14–18 days in summer and every 18–24 days in winter, without the long dry rest given to the fasciata.
At the same time it grows best at 50–65 % relative humidity. In a dry heated room the windows dull and the tips curl inward. A pebble tray under the pot, kept topped up, solves this without wetting the crown — but never mist the rosette itself, because water sitting in the leaf whorl at 20 °C causes crown rot in about six days.
Divide offsets at 1.5 cm, not later
This is the opposite of the fasciata rule. H. cooperi offsets sit on a short rhizome and separate cleanly, and because the mother is small, a pup left too long distorts the rosette symmetry. Take them when the pup is about 1.5 cm across with three or four of its own leaves.
Tease the pup free with a fingernail at the attachment point rather than cutting; the rhizome snaps cleanly. Pot in the same akadama-heavy mix and water after four days. New roots appear in 12–20 days and the pup will have matched the mother's diameter within one season.
Reading the window as a health indicator
Window clarity is the fastest diagnostic on this plant. Fully clear with visible internal veining means light, water and humidity are all in range. Slightly milky means light is marginally high — move it 30 cm further from the source. Clear at the edges but opaque at the centre usually means the plant is dry and the light is too strong at the same time.
A rosette that has gone uniformly pale green with no visible striping at all is almost always over-lit rather than under-watered, which is the opposite of the usual succulent diagnosis. Reduce light first and give it two weeks before changing anything about watering.
Parameter table
- Latin name
- Haworthia cooperi var. truncata
- Common name
- Window Haworthia
- Rosette form
- stacked
- Light range
- 4,000–12,000 lux
- Water interval
- 16 days at 24–28 °C
- Rest period
- No dormancy; the leaf windows cloud over if light exceeds 20,000 lux
- Hardiness
- 10–11 (protect below 5 °C)
- Offset behaviour
- Free offsetting from the base once the rosette exceeds 3 cm, 3–8 per year
- Soil mix (by volume)
- 1 akadama : 1 pumice : 1 kanuma, 2–4 mm
- Mature diameter
- 7 cm
| Month | State | What the plant wants |
|---|---|---|
| January | Growth | Deepest rest. Water only if the lowest leaf ring softens; keep the room as bright as you can. |
| February | Growth | Late rest. Daylight is returning — begin adding an hour of supplementary light every two weeks. |
| March | Growth | Repotting window opens for summer growers. Trim roots, refresh the mineral fraction, dry for a week. |
| April | Growth | Growth restarts. First full watering at the rim, then resume the published interval. |
| May | Growth | Peak growth and the offset season. Feed at quarter strength every third watering. |
| June | Growth | Lengthening days, rising heat. Watch the leaf turgor test rather than the calendar. |
| July | Rest | Out of action for this genus — no water unless the plant visibly shrinks, and no repotting. |
| August | Rest | Out of action for this genus — no water unless the plant visibly shrinks, and no repotting. |
| September | Growth | Autumn window for winter growers. Root-prune and repot while the soil is still warm. |
| October | Growth | Peak autumn growth. This is the season when most colour work should be done. |
| November | Growth | Daylight falls fast. Taper watering by a quarter and stop feeding entirely. |
| December | Growth | Slow, dry and bright. This is the colour peak for most genera in the collection. |
Tinted rows are the months this genus is genuinely out of action: no repotting, no feeding, and water only if the plant visibly shrinks.
Four things to take away
- Target 6,000–9,000 lux measured at the leaf tips; over 20,000 lux clouds the windows permanently.
- Water every 14–18 days in summer, 18–24 in winter; this is not a long-dry-rest species.
- 50–65 % humidity via a pebble tray — never mist into the leaf whorl.
- Take offsets at about 1.5 cm; they root in 12–20 days.
Informational only — This page is a cultivation record, not horticultural or plant-pathology advice. Any treatment should follow the product label and local regulation.