minimum temp for Nerine?

Max Withers
Mon, 30 Aug 2010 16:34:10 PDT
    David linked to Graham Duncan's _Curtis's_ article on N. ridleyi, 
which described that plant's environment thusly "Occurring at high 
altitude, the plants are sometimes subject to snowfalls and sub-zero 
temperatures for several days at a time in winter."

Duncan's subsequent summary of "the Dutch research" (Van Brenk, 
G. and Benschop, M. (1993). Nerine. In: De Hertogh, A. and Le Nard, 
M., The Physiology of Flower Bulbs: 559--588) is therefore confusing:
> Studies carried out in The Netherlands with N. sarniensis, the 
> second-most notorious species for erratic flowering performance, have 
> shown that initiation of a flower bud occurs every year in mature 
> bulbs at the beginning of the growth cycle, directly after flowering. 
> During the following growth cycle, the flower bud differentiates into 
> its component parts such as tepals and stamens and during the third 
> growth cycle the bulb flowers. The cycle therefore takes three years 
> from initiation to flowering and at the end of each growth cycle, a 
> mature bulb contains two flower buds at different stages of 
> development (Van Brenk & Benschop 1993 <#b8>). These studies have also 
> shown that initiation of the flower bud in N.sarniensis is independent 
> of temperature, but that growth of the flower bud is greatly dependent 
> on it. The oldest flower bud will only develop and flower successfully 
> within a fairly high temperature range and the optimal temperature for 
> this to occur is between 17° and 21°C. If the temperature drops to 
> below 17°C, the flower buds are aborted (Van Brenk and Benschop 1993 
> <#b8>). These findings may or may not be relevant to N. ridleyi but 
> are mentioned here as a possible aid to inducing flowering in this 
> species. Like those of the three other winter-growing species, the 
> bulbs of N. ridleyi may well be stimulated to flowering in response to 
> fire, which could be simulated by burning a layer of straw or dry 
> leaves and twigs over the tops of the bulbs in late summer.

(This discussion is in the context of how shy N. ridleyi is to flower, 
even in situ.) The temperature discrepancy can perhaps be explained if 
the optimal temperature range described is for the dormant, i.e. summer 
period? There is a further discrepancy about the number of years the 
flowers take to form -- I believe Nick de Rothschild just said 2, not 3, 
on this list. At any rate, I will endeavor to track down the original 
work, unless someone has a copy handy.

I discovered another inaccessible article that I will also try to 
procure is I ever have time:
Title: Bulb and inflorescence development in Nerine sarniensis
Author(s): Vishnevetsky J, LilienKipnis H, Azizbekova N, et al.
Source: ISRAEL JOURNAL OF PLANT SCIENCES   Volume: 45   Issue: 1   
Pages: 13-18   Published: 1997

As an aside, I am intrigued by the idea of a small fire to induce 
flowering. Has anyone actually tried this? I think I will collect the 
prunings from my Protea to simulate an authentic Fynbos burn.

Max Withers
Oakland CA

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