Crassula helmsii (Kirk) Cockayne

This species’ habitat figures, and what two fixed rules read from them.

The rain rule reads no season: 70% of the year's rain (510 mm of 682 mm) takes 8 months, May to December. Mean temperature moves 10.1 °C between the warmest and coldest month. Months are the habitat's, southern hemisphere; shifted six months for a northern-hemisphere collection: November to June.

Read from the median year of CHELSA monthly rainfall and mean temperature across the envelope cells: the rain rule takes the smallest set of months carrying 70% of the rain and calls it winter when its mean is more than half a degree below the year's, summer when more than that above, and neither in between; the temperature rule, used only under 120 mm, names the cooler six months when they are at least a degree cooler than the other six. Months are shifted for the other hemisphere only where the temperature curve gives a season to reverse. A reading of the curves, not an observation of the plant.

This species’ habitat figures, with their source.

682 mm a year at the habitat, 510 mm of it May to December. Wettest month August at 70 mm, driest February at 39 mm. Across the envelope cells the year's total runs 480 mm to 934 mm (10th to 90th percentile of each cell's own year) (median year across the envelope cells, CHELSA; habitat calendar, southern hemisphere).

CHELSA monthly precipitation, median year across the envelope cells. The rain that falls where the species is recorded; nothing about how the plant takes water.

This species’ habitat figures, with their source.

Open sky over the habitat: 12 to 45 mol/m²/day across the year (daily light integral, median year across the envelope cells, CHELSA; the lowest 10th-percentile month across the cells is 10, the highest 90th-percentile month 49).

CHELSA shortwave radiation at each envelope cell, a daily-mean flux taken to a daily total and converted at 2.07 mol of PAR per MJ. The sky over the habitat, measured; what reaches a plant under a rock, a shrub or a shade cloth is not.

This species’ habitat figures, with their source.

Coldest: the 1st-percentile night over 44 years at the typical cell is 2.1 °C, the absolute minimum -2.2 °C, 19 frost nights in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 36.5 °C. Monthly means: coldest night 5.2 °C in July (across the envelope cells 1.9 °C to 8.6 °C), warmest day 24.5 °C in January (median year across the envelope cells, CHELSA). Cold floor: 2.1 °C, which is the 1st-percentile night over 44 years at the typical cell (NASA POWER).

NASA POWER daily minima and maxima 1981–2024 at the typical cell, lapse-corrected to its elevation; CHELSA monthly means, median year across the envelope cells, CHELSA. The cold floor is the figure named in its sentence. Not a measured survival limit for any plant in a pot.

Relative humidity at the habitat: 56 to 63% across the year (monthly means, median year across the envelope cells, CHELSA). A figure about the air, saying nothing about how the plant takes water.

CHELSA relative humidity, median year across the envelope cells.