"Can anyone comment on this?"

I'm not sure what you want to know. Sheffield's provides instructions for each type of seed. If you want a second or third opinion, just google the scientific name of the particular plant along with the word germination. Chances are that you'll be able to find multiple sources of info. You can also directly check these sources:

The Seed Site
Backyard Gardener Seed Germination Database
Ontario Rock Garden & Hardy Plant Society Seed Germination Guide
Tom Clothier's Germination Database
B&T World Seeds Database

"For the first three, is 120 days right? That's four months stratification - seems long."

Lots of seed types need extended stratification periods. I'd go with the recommendations of those that have done the research.

"For the A. nigrum - am I likely to get decent germination rates from these 1 year old seeds?"

Sheffield's rates don't always reflect the germination rates you will achieve. They represent what they believe could be achieved, in ideal conditions, based on their viability tests of that seed lot. Acer seeds are notoriously more difficult to germinate than many "easy" types of seeds, so results will depend on how well you can give the seeds the conditions they need (especially including proper stratification).

Brandon7

This post was edited by brandon7 on Mon, Dec 2, 13 at 22:13

Thanks.

It's funny they're considered difficult, since the seedlings pop up where I DON'T want them without any difficulty at all...