Warm or cold?

This is the question….Delphinium nudicaule and Iris suaveolens B17Dob make an odd pair for a post but the germination info has to be updated  for both.

Delphinium nudicaule: I wrongly assumed it would be a warm germinator last fall; sorry about this.
My little pot sat under the lights for a few weeks with no action. What to do now? There are two options:

1. Keep the pot outdoors in your pile of all others 2+ years germinators (I have quite a few of them).
2. If you don’t have such a pile, place it in the fridge (enclosed in a plastic bag/box to avoid desiccation).
   

   Cold-moist stratification provided in the fridge

Usually I would do the first and let nature take its course but being a new species for the shop and without reliable info, I want to see precisely how much cold it needs. It went in the fridge as of April 1st (together with few other species).

If you go the ‘fridge way’ don’t forge to mark the date and to open the bag and check the pots periodically.

 

Iris suaveolens B17Dob (offered in the fall/winter of 2017)

With some Irises it is more complicated: many species won’t germinate simply because they have very hard seed coats. Cold/warm cycles will wear down the seed coat and allow the water imbibition and emergence of the radicle. But this doesn’t mean that the species ‘requires’ a cold period, i.e. has a physiological dormancy; often the lines are blurred.

Although I sowed my seeds in early fall (2017), they didn’t germinate in the spring of last year (2018). I don’t know if they will germinate this spring either. All I know is that the seeds are good (viable) and like in the case of many Iris species, it is the hard seed coat that delays the germination.

In late January I tried the ‘forced method’ recommended for aril irises on a small sample of Iris suaveolens B17Dob – not having experience, I destroyed most seeds but one I got right and it’s enough to prove the point: the seeds have a very hard tegument but otherwise it would be a warm germinator (probably like many others). You can open the link to read about this method: http://files.srgc.net/general/ForcedArilIrisGermination.pdf
Remains to see how long it will take for the seeds sown outdoors to germinate.

Conclusion: I emphasize again the advice that gets sent with all seeds orders: “keep your pots for at least 2(3) years”.
It can happen that even species known to germinate at warm or cold will decide not to do it. The collection site/region/mother-plant and few other factors can influence the patterns of the germination.