On a recent visit to Strassbourg, I came across some pods of the honey
locust tree Gleditsia triacanthos which grows abundantly in the park near
the European institutions.

I prised some seeds out of the pods and have tried to get them to germinate.

After various freeze / thaw treatments I planted the seeds in compost and
waited ... ...

After a month or two I grew impatient and so dug out the seeds. None has
germinated. They were exactly as planted - just as hard and shiny.

I attempted to scrape one with a sharp knife - for hours with little impact
at all, though i did get down to a slightly paler shiny hard surface in
parts.

Growing impatient again, and this time thinking that the sweet pods would
expect to be eaten, I placed the seeds in a thermos flask with blood heat
water and some wine vinegar for 24 hours. The seed I scraped swelled up to
twice the size and I could prize off the remaining hush. The unscraped
others are completely unaffected by the treatment - just as shiny and hard
as ever.

The one seed has a yellowish inside layer and two outer layers of what look
like semi-transparent plastic which get a little gooey on the surface.
There is still no sign of germination.

What am I doing wrong? What am I to do?

Surely a plant as common in the USA as the honey locust should be relatively
easy to germinate by a natural means?

Has anyone got any experience of this intriguing but irritatingly obtuse
plant?

regards
Don