summer dormancy (was Blue bulb and similar)

Peter Taggart
Sun, 14 Aug 2011 04:36:28 PDT
Thank you Lauw, you are very kind.
There are many details that might be added to my original statement.I know
that you and many others will already know a lot more than I do about this,
but there will be a lot who don't, so please correct any errors I write.

I gave my original reply because  recentlyseveral people, in climates too
hot or too wet for these plants, have mentioned chilling these plants for
the summer. This sounds to me as if there is a complete misunderstanding of
the growth pattern. The plants from these climates need to be dry NOT cold
in summer.

One such detail is that Crocus are corms and not bulbs, The process and
timetable of flower bud formation is different in corms to that which I
described in bulbs.

However for Mediterranean and Continental climate bulbs, corms and almost
all geophites the overall growth pattern is as I described.
Due to the difference in flower development between corms and bulbs I would
suggest corms might be easier to maintain and flower in hotter/ subtropical
climates, rather than true bulbs?

For true bulbs, chilling them will extend the winter growth period,
(allowing more time for flower bud development in the bulb,) before top
growth appears. BUT first the plants need a warm, dry summer! How warm and
how dry depends on the species.
The reason I am suggesting chilling the plants, is to allow a climate with
perhaps only three months of cooler weather, an early start into growth, at
the beginning of the very short growing period.
In the case of true bulbs it might also help prevent the flowers aborting.
Heavy feeding might also help build bigger bulbs/ geophytes, if trying to
grow them in such a short winter growing season.
I have never gardened in the subtropics but I sympathise with those who wish
to grow plants suited to climates that they don't live in.

for all those in summer wet or subtropical climates who don't know:

Peter (UK)

On Sun, Aug 14, 2011 at 10:42 AM, contact <> wrote:

> Hello Peter,
> A very concise and  clear explanation. This also explains why in some cases
> typically mediterranean bulbs (such as Crocus) are grown in a  cooler
> climat
> (per example  UK or  the Neherlands) produce a much better size because of
> the long  springtime growing period.  When here  the leaves are drying off
> in April, in Holland the growth goes on until early June. Of course  in the
> Dutch climat the growers have to make some artificial arrangements to
> obtain  warm and dry summer conditions.
> Kind regards
> Lauw de Jager
> South of France
> -----Original Message-----
> Temperate continental climate bulbs basically root following rain and/ or
> fluctuating temperatures before winter, they may then slow down, while
> frozen, untill thawing/ snowmelt/ spring time. They then go dormant for a
> (hot) dry period in summer which stimulates the setting of flowerbuds
> within
> the bulb. The cycle is started again by fluctuating / cooler night
> temperatures and water before winter. If they dont get enough cold in
> winter, the embryonic flowerbuds will not have time to develop before
> spring, and I would expect lots of leaf instead and aborted flowers. Alpine
> houses are often kept frost free in the uk, and this is fine for these
> bulbs. The winter cold dormancy after rooting and before top growth is
> enforced by giving only a very little water untill top growth is required.
> I
> expect that the biggest problems you might encounter in a hotter climate is
> that when the bulbs get warm they must be allowed to go dormant (and dry)
> or
> they will rot. This may be before they have finished a full seasons growth
> resulting in poor bulbs for the following year. I think keeping them cool
> to
> achieve a long spring growth period
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