Zantedeschia hardiness

John Grimshaw
Tue, 16 Jun 2009 10:33:30 PDT
Jim McKenney wrote:
> I've had problems with Z. aethiopica too, but I think the root of that is
> that this species is a winter grower which only very reluctantly changes
> seasons.

This issue has been touched on but I think not yet fully explored. 
Zantedeschia aethiopica has a wide range in South Africa, encompassing both 
winter and summer rainfall areas.

It seems sensible to me to assume that most importations of Zantedeschia 
aethiopica have been from the area around Cape Town, where it is very 
common, even growing at the very tip of Cape Point. These winter growers 
would certainly be tender in northern Europe, necessitating the glasshouse 
culture/underwater techniques to survive.

I have collected seed of Z. aethiopica on the Sani Pass, in Kwa-Zulu-Natal, 
a classic summer-rainfall location and source of many hardy plants for UK 
gardens. The seedlings are absolutely hardy here and flower in midsummer.

Mulling over it, I came to the thought some time ago, that the generally 
reliably hardy clones in the UK, e.g. the old but unspecial 'Crowborough' 
and the recently named 'Glencoe', are probably from the summer-rainfall 
area, though this is impossible to prove. If so, it demonstrates the 
importance of provenance when selecting South African material for garden 
use. (Another plant with similarly wide distribution  in SA & reputation for 
tenderness is Melianthus major: again, one suspects that most seed has come 
from the Western Cape, and one wonders how material from the Drakensberg 
would fare.)

The pink-throated form of Z. aethiopica also seems to be entirely hardy 
here, and occurs in eastern south Africa somewhere as a wild plant.

Z. albomaculata survives outside here, but is late to emerge, and does not 
flower very freely.

John Grimshaw

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Dr. John M. Grimshaw
Sycamore Cottage
GL53 9NP

Tel. 01242 870567

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