minimum temp for Nerine

Michael Mace
Mon, 30 Aug 2010 18:45:49 PDT
Diane wrote:

>> Does this explain why my sarniensis hybrids don't bloom frequently?

Just to join the chorus here, I seriously doubt that report about
temperatures.  I get some bloom here from N. sarniensis grown in the open,
where winter lows usually hit about -7C in the depths of winter.

I looked up the book in question on Amazon:…

Fortunately, they let you search inside the book's contents and look at a
few pages.  All I can say is, I want this book!!  It summarizes a huge
amount of bulb growth information that has been developed by Dutch growers.
Keep in mind that their main goal was to figure out ways to farm these
bulbs.  So a lot of the experiments focused on things like how to force and
delay blooming.  That means some of the results may not be relevant to
gardeners.  Still, the material is really interesting.  Some tidbits:

--The book has information on blooming for all sorts of different Nerines,
and the effect of temperature varies from species to species.  N. bowdenii
flowered better with a relatively high storage temperature (17-25C), but N.
flexuosa failed to bloom at all with those temps; it required 9-13C.

--Regarding N. sarniensis (p. 572), there are several points: 
    The experiments were all on Nerine sarniensis corusca 'Major'
    The plants need a variation in temperature in order to bloom well:
Relatively warm at bloom time, and relatively cool after that to encourage
roots and leaves.  
    A soil temperature range of 17-21C (62-70F) at bloom time (fall)
produces the best blooming.  If temps are lower during bloom time, leaves
and roots will grow a lot, but the flower buds may abort.  On the other
hand, growing at 25C/77F or above tends to produce rot.  
    3-6 weeks after flowering, temps need to be dropped to 9-12C (42-55F) in
order for the bulbs to develop properly.  If they stay too warm, the bulbs
make lots of leaves and roots, at the expense of the bulb itself.  The bulbs
then tend to die during the dormant season.
    Storage of the bulbs for six weeks out of the ground in summer at 17C
(62F) produced earlier flowering (but not more flowers), as compared to
leaving he bulbs planted, or stored out of the ground at cooler
temperatures.  The flower bud inside the bulb lengthens while the bulb is
otherwise dormant, and warm storage pushes the development of the bud
    Light intensity makes no difference in flowering, but the bulbs grow
best if they get good light when in leaf.
    To summarize: plant in the fall and grow at 17-21C (62-70F).  After
flowering is finished (around November in the northern hemisphere), reduce
temperatures to 9-12C (42-55F) or possibly lower -- temps lower than 9C were
not tested in the research.  In the spring, gradually increase temperature
as the foliage starts to yellow.  Bulbs are generally dormant by the end of
April, and should spend the summer in the 17-21C (62-70F) range.
    Other notes:  pH of 6-7, avoid salts in the soil.  If you lift the bulbs
when dormant, do not damage the young unbranched roots; they will grow and
support the plant in the next season.  

So, Diane, here's what I think that means for your conditions in BC:  

--Make sure the bulbs are staying warm enough in the summer and fall so that
the buds don't abort.  Keep temperatures around 20C/70F (not much higher,
not much lower).  That's soil temp, not air temp.

--After blooming, temperatures can go lower (in fact, they need to).  But
you need to make sure the bulbs get a lot of light.  I wonder if that might
be a challenge at your latitude. 

I'll adjust the information on the wiki.

San Jose, CA

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