Crassula perforata: reading the red rim as a temperature log
String of buttons grows as opposing pairs of triangular leaves fused at the base, so the stem appears to pass through them. That structure makes it the easiest Crassula to grow straight and the easiest to read: the red rim is a record of the cold it has seen.
The red rim is a cold log, not a light log
Unlike most succulents, the red margin on C. perforata is driven primarily by night temperature rather than light intensity. Plants held at 16–20 °C nights in good light stay entirely green; drop nights to 8–12 °C and the rims colour in ten to fourteen days at the same light level.
This makes it a useful canary in a mixed collection: if the perforata rims are red and the Echeveria next to it is still grey, your nights are cold and your days are not bright. That pairing tells you which variable to change.
Growing single stems straight
The stacked growth means each stem is a vertical chain with no branching unless forced. Left alone, one plant becomes three or four leaning columns that fall over at about 30 cm. The fix is early: at 10 cm, cut the stem into 4 cm sections.
Every section is a viable cutting. Lay them on dry mix for three days, then stand them upright with the base just touching the surface. Each will root in 14–21 days and, more importantly, each cut stump branches into two, so a single plant becomes a compact cluster rather than a leaning column.
Watering on a 15-day cycle with a winter extension
At 24 °C in a 12 cm pot the mix dries in 13–17 days. The plant's signal is unusually clear: the paired leaves lose their tight overlap and a visible gap opens between successive pairs on the stem. Water when the gap is roughly 1 mm at the top third of the stem.
In winter at 10 °C, extend to 25–30 days and expect the plant to keep looking good throughout — this is one of the few Crassula that does not deflate or drop leaves in a cool rest period. If the pairs start to wrinkle longitudinally, you have gone one cycle too far.
The one pest that matters: mealybug in the leaf axils
The fused leaf pairs create a shallow pocket at every node, and that is exactly where mealybug establishes. It is easy to miss because the pocket faces upward and is only 2–3 mm deep. Check by parting the top three node pairs with a toothpick; look for white cotton and a sticky sheen on the stem.
Treat by dabbing each pocket with a 70 % isopropyl swab, then repeat every seven days for four weeks to catch the hatching cycle. Water the plant sparingly during treatment — the alcohol plus wet mix at the same node is the one combination that reliably rots a stem.
Parameter table
- Latin name
- Crassula perforata
- Common name
- String of buttons
- Rosette form
- stacked
- Light range
- 25,000–45,000 lux
- Water interval
- 15 days at 24–28 °C
- Rest period
- Slows below 8 °C but keeps colour; red edges strongest December to March
- Hardiness
- 9b–11 (damaged below −1 °C)
- Offset behaviour
- Branches from the base after a cut; stems also root wherever they fall and touch mix
- Soil mix (by volume)
- 2 pumice : 1 akadama : 1 grit, by volume
- Mature diameter
- 30 cm
| Month | State | What the plant wants |
|---|---|---|
| January | Rest | Out of action for this genus — no water unless the plant visibly shrinks, and no repotting. |
| February | Rest | Out of action for this genus — no water unless the plant visibly shrinks, and no repotting. |
| 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 | Growth | Hottest weeks. Water in the evening, a third of the spring volume, and only on a visible symptom. |
| August | Growth | Heat eases at night. Prepare mix and pots for the autumn repotting window. |
| 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 | Rest | Out of action for this genus — no water unless the plant visibly shrinks, and no repotting. |
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
- The red rim tracks night temperature, not light — 8–12 °C nights colour it in ten days.
- Cut stems into 4 cm sections at 10 cm tall; every section roots in 14–21 days.
- Water when a 1 mm gap opens between leaf pairs in the top third.
- Check the leaf pockets for mealybug with a toothpick; treat weekly for four weeks.
Informational only — This page is a cultivation record, not horticultural or plant-pathology advice. Any treatment should follow the product label and local regulation.