Hardiness of ixia and Sparaxis

Lee Poulsen wpoulsen@pacbell.net
Tue, 04 Apr 2006 14:41:07 PDT
On Apr 4, 2006, at 12:10 PM, Jim McKenney wrote:
> Adam, before I joined this list two years ago - which is to say before 
> I was
> much aware of the variety of temptations in the southern African flora
> But as you probably know from reading the postings on this list, most
> successful growers have their plants blooming during relatively cool
> weather.
> But there is a bigger problem. In my experience, these plants are 
> rigidly
> stuck on a winter growing cycle.
> In my experience, the problem with these plants is not simply that 
> they are
> or are not hardy; the real problem is that they are inveterate winter
> growers.
> Not all of the plants you mentioned are winter growers.

The big deal with southern African flora, especially those from South 
Africa, is knowing which are winter-growing, summer-dry plants, and 
which are summer-growing, winter-dry plants. These two correspond, with 
only a few exceptions, to which side of South Africa they are native 

If you draw a roughly north-south line roughly about 1/3 the way in 
from the west coast (or 2/3 the way in from the east coast), this marks 
the boundary of sorts between the two completely opposite annual 
rainfall patterns that predominate in South Africa. The west coast 
third of the country is the winter-rainy, summer-dry (mediterranean) 
rainfall pattern, and the eastern two-thirds of the country is the 
winter-dry, summer-rainy, more humid, rainfall pattern and climate. In 
whichever half of the year that rain falls, this will also be the time 
when plants will be in major growth. So plants and bulbs that originate 
from one of these two region will, as Jim says, tend to be rigidly 
stuck on that particular annual growing cycle. Curiously, flower season 
is completely independent of this--some plants bloom in the dead center 
of their dry season, with either no leaves or a dormant plant that will 
suddenly have a flower scape appear on it, like Amaryllis belladonna 
does with summer flowers or Aloes with winter flowers.

(There are a very few plants that grow in both regions, or are native 
to the southern coast--which is the one anomalous, 
constant-rainfall-all-year region of South Africa--where you may be 
able to force it into one or the other growth cycle. Or it may be 

Since such a huge number of species of geophytes in particular come 
from the western (also known as the Western Cape) region, it might seem 
that almost all bulbs that came from South Africa are winter growers. 
But it turns out that this is not the case. So some of the ones that 
Jim mentioned as growing well on the U.S. east coast (like Eucomis and 
Crinums; also some of the Nerine species) originated in the summer-rain 
2/3 portion of South Africa. This reminds of another thing to keep in 
mind: Some genera have evolved different species in both regions. As 
Rachel Saunders can tell you, you should grow them (and plant the 
seeds) for the different species corresponding to when the rainy season 
falls in their location of origin regardless of whether they are in the 
same genus. And Rachel, for example, will list that in her seed 

The other factor that comes into play is that plants that come from 
higher elevations will tend to be hardier to colder temperatures. Thus, 
you find people like Jim Shields (who lives in Indiana) who are always 
looking for species that are native to the eastern two-thirds at high 
elevations, such as the Drakensberg, including Lesotho (an independent 
country inside of South Africa). I would think that those who live in 
the eastern half of the U.S. above USDA Zone 8 would be the most 
interested in these kinds of plants since they seem to have the highest 
chance of surviving in that climate. (This would be things like some of 
the Kniphofias and maybe some of the Dieramas. I'm not that familiar 
with all the natives of the higher Drakensberg areas since those are 
the least likely to be happy with my climate conditions here in 
southern California.)

Anyway, for those of you so inclined to look at data plots, Mary Sue 
has placed on the wiki some annual rainfall plots I made several years 
ago of various locations throughout South Africa which I grouped into 
six different rainfall pattern regions.  See 
about halfway down.

Okay, maybe that was too much information. But I think it's helpful in 
trying to guesstimate what might survive or even thrive in my 
particular climate.

--Lee Poulsen
Pasadena, California, USDA Zone 10a

More information about the pbs mailing list