Plant of the Week
Living Stones
Latin: Lithops sp.
Failure is a part of gardening. I often tell people that if you don’t
occasionally kill a few plants, you’re not trying hard enough.
Having killed more than my share of houseplants over the years, I’ve
gradually come to the conclusion that succulents best fit my style of benign
neglect. Yet, even some of these desert dwellers prove elusive, including the
living stones.
Living stones are stemless succulents from South Africa that belong to the
ice plant family. In nature they grow almost completely underground with only a
pair of kidney shaped, succulent, flat-topped leaves exposed to the sky. The
visible portion of the leaves function as a skylight and are mottled with green
and brown and reach the size of a quarter.
The leaves look like the paintings of Northwest Arkansas’ artist, George
Dombek, when he was in his "pebble" period, except that the plant has a cleavage
line between the two leaves. The inside of each leaf is a transparent gelatinous
mass which transmits light from the skylight to the side walls of the leaf where
photosynthesis occurs.
In the spring, and sometimes in the fall, yellow or white cactus-like
flowers, usually larger than the plant itself, emerge from the cleft between the
two leaves. The resemblance of the living-stones’ flowers to those of the cactus
family goes beyond superficial appearance and includes a unique set of pigments
found exclusively in the two families.
These pigments point to a common ancestor of modern day cacti, which are
native only to the New World, and members of the ice plant family which are
found in Africa. It’s theorized that when South America and Africa were joined
as one mammoth continent called Gondwanaland during the Cretaceous Period -
about 100 million years ago - this ancestor was isolated into two communities
when the continents drifted apart. Through eons of evolution the cactus family
took on the familiar barbs for protection in arid climates while the African
relatives developed a less prickly means of survival.
The living stones produce seeds in a capsule, which opens to expel seeds when
it is moist and close to protect them when dry weather returns. These capsules
are the main means of classification of the family. The ice plant family
contains a number of Lithops-look-alike genera and, if DNA technology is ever
brought to bear on the family, no doubt the relationship lines of the group will
be significantly reordered.
The last batch of living stones I grew - and until the squirrels attacked
they were actually growing - were an assortment of year-old seedlings in 2-inch
pots. I’ve not sorted out in my own mind if squirrels are curious or just mean
spirited, but they certainly seem to love the leaves of these fat little
succulents. Lithops require well drained, gritty soil and bright light to
survive. Because over watering is a constant threat, they are usually kept in
small clay pots.
Typically, in their native haunts, they have two periods of inactivity during
the year. During these periods of rest, watering should be reduced greatly. The
rest periods are during our winter and summer months. In the spring and fall,
they should be watered once or twice a week but never allowed to sit in a saucer
that will hold water. Fertilization is on the light side, but a diluted
houseplant fertilizer should be used during the beginning of the growth spurts
of spring and fall.
By: Gerald Klingaman, retired
Extension Horticulturist
- Ornamentals
Extension News -
May 25, 2001
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