Haemanthus Season (What Causes This?)

J.E. Shields jshields@indy.net
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:


Jim Shields
in cool, sunny Westfield, Indiana

At 05:19 AM 8/27/2010 +0100, you wrote:
>Winter-growing Haemanthus are also coming into flower here - buds appeared 
>in the dry resting pots a few days ago and are expanding rapidly now that 
>they are being watered. Cooler temperatures (or a sudden drop in 
>temperature) may be a trigger and seem more probable than daylength. We 
>have certainly progressed into cool 'autumnal' weather - has anyone else 
>noted a cooling event that could have caused flowering to start?
>John Grimshaw

Jim Shields             USDA Zone 5             Shields Gardens, Ltd.
P.O. Box 92              WWW:    http://www.shieldsgardens.com/
Westfield, Indiana 46074, USA
Tel. ++1-317-867-3344     or      toll-free 1-866-449-3344 in USA

More information about the pbs mailing list