germinating gladiolus

Diane Whitehead
Mon, 17 Mar 2008 16:00:19 PDT
I have begun an analysis of my gladiolus germination, which I hope  
will be useful to someone.

The seeds have been mainly from Silverhill and Gordon Summerfield,  
with a few from alpine seed exchanges.

I sow them when I get them, the only safe thing for me to do (When I  
was cleaning up for Christmas, I discovered a bag of unsown surplus  
seeds from 2004 - the big exchanges  sell the seeds left over from  
their midwinter frenzy, and the price is too low to pass up.   
Unfortunately the seeds arrive in the middle of Easter egg hunts in  
the garden with all the grandchildren, or tomato transplanting time -  
so these ones were tidied away till they were found over 3 years  
later.  Amazingly, a lot have germinated.)

Back from the digression.

I know that South African seed is supposed to be treated to a daily  
change in temperature, and for about a week once I did manage that.  I  
had the bag of seeds in the fridge next to the milk at night, and in  
the morning, I'd remember to bring them out into the warm kitchen, and  
put them back each night.  Too much to expect of anyone whose main job  
isn't germinating seeds.

So they get a fairly constant temperature, whether sown in summer or  
winter.  I keep them in the living area of my house which is heated in  
winter to about 18 C  (70 F) in the daytime and a bit lower at night.   
If they are sown in summer, the house maintains about the same  

When they germinate, I put them in a pot in my unheated greenhouse  
which maintains a stable temperature as it is very big - right now, it  
is 10 C outside, and 15 C inside the greenhouse, and mimosa is  
blooming - about 4 m high.

I've sown 80 packets of Gladiolus seed up to mid-January 2008 (I've  
made that the cutoff date because some of those have germinated.)  So  
far, 19 have not germinated, 6 of them being Mediterranean, and the  
others South African.

The fastest:
leptosiphon  7 days
involutus   10 days
buckerveldii and pole-evansii 14 days
huttonii  17 days
flanaganii  and geardii   20 days
hirsutus 23 days

The slowest:  (of those which have germinated)
kotschyanus and some unknown species from Iran  1 year
natalensis 18 months

I don't know how long seeds will remain viable but ungerminated (like  
my 8 year old Colchicum seeds).
The oldest ungerminated Silverhill seeds:  maculatus  sown in July  
2006 and trichonemifolius in November 06. I should dump them out to  
see if they are still sound.

Diane Whitehead
Victoria, British Columbia, Canada
maritime zone 8, cool Mediterranean climate
mild rainy winters, mild dry summers

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