Ecology
Where
Gasteria grow almost exclusively on RSA territory. Only G. pillansii is also found in southern Namibia. The map below shows the distribution of the genus.
copyright Jan Vandorpe 2022
It is clear from the map that all Gasteria occur within a 300km zone from the coast. A lot of species occur even within a few km from the coast or even at the coast. This might mean they need a minimum amount of moisture and expect it to be delivered at regular intervals.
Habitats
In my humble opinion, one can distinguish the follwoing major habitats
G. rawlinsonii in Baviaanskloof
Rock faces
Plants grow on vertical cliffs along rivers and in ravines.
Advantages are:
in shade but lots of light
safe from predation
dispersal along river system
G. langebergensis under bush
Under bushes
Gasteria very often grow hidden under a 'nursery bush' on rocky slopes
Advantages:
shaded from direct sunlight
hidden and protected from predators
seedlings find the right environment for growth
G. acinacifolia near Port Elisabeth
Open environment
A few species (acinacifolia, nitida) grow in the open in full sun. Ususally in a windy environment
Advantages:
lots of light
lots of wind (seed dispersal)
G. pillansii var. ernisti-ruschii in the Huns mountains, Namibia
(© photo Derek Tribble)
Mountain summits
Plants grow amongst rocks high up mountain ridges .
Advantages:
cooler environment
lots of light and moisture
dispersal along ridge
Climate
In what kind of climate do Gasterias grow? One might wonder if one could replicate it ...
Simplified climate map (Köppen)
Comparing the map on the left with the species distribution map tells you that most species grow in one of the following climate zones:
Bwk (cold desert climate)
Bsk (cold semi arid)
Bsh (warm semi-arid)
Cfb (temperate oceanic climate)
Cwa (Humid subtropical)
This means that all species experience some form of seasonality: dry/wet and cooler/hotter seasons and almost none have real cold winters with frost.
They also have a measurable day/night temperature difference.