Haemanthus Season (What Causes This?)
J.E. Shields (Fri, 27 Aug 2010 05:30:31 PDT)

At most, we had somewhat less hot weather when the first buds appeared in a
few pots of Haemanthus here. So perhaps a *relative* drop in (nighttime?)
temperatures might trigger things for the Western Cape and Namaqualand
Haemanthus species. Given that Berkeley is on nearly the same latitude as
Indianapolis, 40°N, our synchronization could be attributed simply to day
length, I suppose. The UK, on the other hand, is far from our latitude so
we are forced to look to other factors.

I think I've read that some plants have an internal calendar that
"remembers" how long it's been since they went dormant or since they last
bloomed, so we can't arbitrarily eliminate long-term entrainment of the
flowering and growth cycles by the environment.

To answer Steve's question: my dormant pots are never watered until I see
the new inflorescence starting to emerge.

So, my guesses, in order from what I think most likely to least likely
triggers for bloom:

1. Relative drops in daily temperatures, from hotter to somewhat less hot.

2. Long term (i.e., annual or even multi-year) entrainment of flowering
cycle by climate

3. Day length changes

4. Water

Incidentally, those pictures of the Haemanthus in bloom are now posted to
my blog at:

http://shieldsgardens.com/Blogs/Garden/…

Regards,
Jim Shields
in cool, sunny Westfield, Indiana
USA

At 05:19 AM 8/27/2010 +0100, you wrote:

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Jim Shields USDA Zone 5 Shields Gardens, Ltd.
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Tel. ++1-317-867-3344 or toll-free 1-866-449-3344 in USA