RE: drought tolerant shade plants

Several South African species of Crassula have solved this problem quite 
nicely as have many Haworthia and Gasteria species.  It's interesting that 
the shade loving Crassula generally are not HIGHLY xerophytic. Most of 
these probably use CAM photosynthetic pathway or are facultative CAM 
plants. I think your correct about energy budgets being a limiting factor.

There are a number of highly xerophytic South African Aizoaceae that shade 
themselves by "contracting" beneath the soil surface during drought periods 
and "emerge" when their is adequate moisture. Many Haworthia use a similar 
strategy. There are also South African Crassulaceae and Aizoaceae that 
occur in shaded niches embedded in otherwise bright and very xeric areas. 
Of further interest is their occurrence in habitats that have very low 
rainfall but frequent "dew fall" or heavy fog components. The actual 
available moisture is not high but tends to be quite consistent for an arid 
zone.

South Africa is a good place to look for plants that can tolerate both 
shade and at least some degree of drought. I have had success growing many 
of these under Eucalyptus.

Phil Bunch


On Saturday, November 09, 2002 13:40, Lisa Van Cleef 
[SMTP:lisavan@pacbell.net] wrote:
> Thanks to everyone for their responses.  I now realize my question
> wasn't phrased properly.  I was looking for an explanation of the
> situation--why there aren't many plants naturally living in dry
> shade-- as opposed to a list of drought tolerant plants--though I
> ain't complaining, I got some fabulous lists.
>
> I thought some folks on this list might be interested in the response
> I got from botanist Martin Grantham:
>
> First I'd think there are some energetic constraints involved. You've
> got to have light, CO2, and water to make a living as a plant.  In a
> shady & wet environment light is limited for photosynthesis, but the
> plant is primed with water to maximize photosynthesis whenever light
> is available. In a bright & dry environment water is limited for
> photosynthesis, but light will be available with any water that comes
> the plant's way. In dry shade two of the things necessary for
> photosynthesis are generally lacking: both light and water. That
> would make a plant's energy economy likely to be much tighter. Fewer
> plants might be expected to have the extreme frugality necessary.
>
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