Lobelia deckenii ssp. keniensis. Photo by Gerard O'Brien.
Lobelias are common garden plants grown for their
floriferous nature and many flamboyant colours. As with most
plants, there are also some species that surprise you and which
are often harder to tell what they are.
Lobelia are no exception, with a group of them often known as
tree lobelias. Using the term tree might be stretching the
imagination a bit, but they can form stems a metre or more
above the ground. This is then often followed by large flower
spikes extending the growth by up to another metre.
One such species is Lobelia deckenii ssp.
keniensis, endemic to Mount Kenya in the mountains of
East Africa. It is characterised by many rosettes of leaves
interconnected by underground rhizomes.
Each rosette increases in size and height over many years
until reaching maturity and flowering.
Water collects in the rosettes of leaves in the moist
environments where it usually grows.
This water is important for its survival during cold weather,
as when the water freezes it protects the growing tip of the
plant from being damaged. The crescent-shaped ice cubes that
form in the rosettes give this plant its common name of gin
and tonic lobelia.
Surprisingly, Lobelia deckenii ssp. keniensis
is surviving well in Dunedin Botanic Garden, due to the
city's climate reflecting that of its native high-altitude
Lobelia gregoriana (previously known as Lobelia deckenii
subsp. keniensis) and another giant African lobelia,
Lobelia aberdarica can be seen in the South African
Garden in the Geographic Collection at Dunedin Botanic
- Dylan Norfield is the geographic and arboretum
collection curator at Dunedin Botanic Garden.