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
temperature.

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