Timing for bulbs changing hemisphere?

John Grimshaw j.grimshaw@virgin.net
Sat, 05 May 2007 00:06:50 PDT
Lee Poulsen wrote; ' I have tried to hold dormant bulbs over an extra 6
> months, but very few bulbs seem to like that'

My view on converting bulbs to opposite hemispheres is that it is very 
important to always consider their natural physiological regime and use that 
to inform one's treatment of them. In September 2004 I brought some 
winter-growing bulbs home from the Cape - a small but varied assortment 
(Romulea, Lachenalia, Nerine, Eucomis regia, a tuberous Crassula etc). They 
had been in the post-flowering stage but dormancy was imposed by removing 
the foliage before packing them. (Sounds brutal but not a problem for most 
bulbs if they've had a few weeks of fattening.)

In the wild the regime would then have been a hot dry period (summer) when 
the bulbs are dormant, followed by a cooler autumn, when the falling 
temperatures trigger root and shoot development, a damp but comparatively 
mild winter when roots and shoots emerge and grow, then spring when the 
plants flower (approx August).

Their first physiological requirement after dormancy is the warm dry 
period - when they are completely dormant. We in the UK were then going into 
autumn with falling temperatures. To pot them then and place them in 
ordinary greenhouse conditions would not give them this and cool dampness 
would probably cause rapid rotting of the bulbs. I also considered that the 
Cape can have extended droughts in which the winter rains are late, or very 
minimal, and in consequence the bulbs are adapted to withstand long dry 
periods in a state of summer dormancy. In consequence I chose to keep the 
bulbs dormant until the following August and did so by putting them in 'just 
moist' vermiculite in ziplock bags and kept them in a bedroom drawer. I 
inspected regularly and on each occasion they were fine, but by August there 
were signs of root and shoot development, so the bulbs were also on schedule 
for a late summer planting. All except the Romuleas worked well and came 
into growth over the autumn & winter months of 2005-06, and have done so 
again in '06-07.

I could have opted to try a spring planting but a) there would not have been 
a long cooling down period to get the bulbs active and growth would have 
been curtailed by rising temperatures in early summer (although the hot dry 
dormant period would have ensued, enabling growth to restart in autumn as 
temperatures drop.)

Following the physiology of bulbs (and seeds) is very important. A few years 
ago I was given a selection of choice Galanthus bulbs in early summer and I 
put them in the salad drawer of the fridge. They were planted in pots in 
autumn. Nothing emerged. But the bulbs were fine and sound - they had not 
had the summer warm dormant season that must precede root and shoot 
rowth  - so they remained dormant for another summer and finally emerged in 
the following season (rather reduced in size but alive) and have since grown 
perfectly normally. I have had similar effects with imported 'perishable' 
bulbs from Holland that had evidently been kept in a cooler - Leucojum 
vernum and Fritillaria species. They sat out the firstseason and came into 
growth the following year.

In keeping such bulbs dormant over extended periods it is esssential that 
they do not desiccate, so they must be packed in some insulating material 
(vermiculite or sand, etc) to prevent this.

John Grimshaw

Dr John M. Grimshaw
Sycamore Cottage
Nr Cheltenham
Gloucestershire GL53 9NP

Tel. 01242 870567

Easter Monday 9 April, Arboretum Weekend 15-16 September
Gates open 1pm, last entry 4 pm
website: http://www.colesbournegardens.org.uk/

----- Original Message ----- 
From: "Lee Poulsen" <wpoulsen@pacbell.net>
To: "Pacific Bulb Society" <pbs@lists.ibiblio.org>
Sent: Friday, May 04, 2007 7:08 AM
Subject: Re: [pbs] Timing for bulbs changing hemisphere?

> On May 3, 2007, at 6:33 PM, Paul Tyerman wrote:
>> Howdy All,
>> I need some brain-picking of experience please?  What is the best
>> time to try to change hemisphere for bulbs and corms?
> I know plenty of others have experience with this too. But as a
> general rule of thumb, the conversions that have worked the best for
> me are when I get a bulb as soon after it enters dormancy in the
> opposite hemisphere as possible, and then try to grow it as long as
> is feasible in what is left of its normal growing conditions in my
> hemisphere. I have tried to hold dormant bulbs over an extra 6
> months, but very few bulbs seem to like that. They shrivel and
> sometimes disappear before the proper growing season begins in my
> hemisphere, especially if they are very small bulbs, which is often
> the case. Now if I can't get them early enough after dormancy I just
> wait another year.
> That being said, I've found that the most difficult type to convert
> hemispheres are the winter growers. Summer growers are easier to
> convert because it's much easier to continue providing them the
> warmer conditions they want on into our late autumn and early winter
> than it is to continue providing cool growing conditions after spring
> has ended and summer here has begun. I have often thought about
> begging friends who lives along the coast here (where they have much
> cooler conditions even into the summer) to let me finish growing them
> at their house. But then I know they won't take care of them
> properly, etc. Now if you live along coastal northern California or
> in the coolest of the San Francisco Bay Area climates, you can
> probably grow them in cool conditions for an extended period after
> receiving them. Same holds for the Pacific Northwest and British
> Columbia. If you have friends in Anchorage, Alaska, that would
> probably be a perfect place to try converting winter growers.
> Our only saving grace in So. Calif. is that we get May Gray and June
> Gloom which makes our early summers generally much cooler than what
> the U.S. Southern states experience. But many of the summer dormant
> species don't do well there anyway because it is so humid and wet
> during their summers.
> Western and Northern Europe probably have a similarly easier go of it.
> --Lee Poulsen
> Pasadena, California, USA, USDA Zone 10a
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