How necessary is winter scarification? And when to plant trees/shrubs?

I'm in the northern hemisphere (New York) in about hardiness zone 6b; if I put tree & shrub seeds in the ground now, will they have enough time to establish themselves before winter, or should I wait til fall for the seeds to go through natural scarification process? I'm planning on planting Russian olive, autumn olive, Siberian pea shrub, honey locust, black locust, choke cherry, ground cherry, barberry, buffalo silverberry, sea buckthorn, elderberry, huckleberry, mulberry, cornelian cherry, and hazelnut.

"Scarification" and "Cold Treatment" are two different things.
Some seeds need one or the other, and some seeds need both.

In nature, seeds that need both, are usually dropped by the tree in autumn.
The winter cold provides the required cold treatment, and microbial activity provides the scarification.
The following spring, once weather is right, germination begins.

Any of your seeds that need cold treatment would probably not survive if planted now unless they have been stored for at least a month or two at temperatures below about 40 degrees (F).

Scarification done by nature takes months to prepare the seed for germination.
It is often done manually as a way to prepare seeds for planting.
Sand paper, or a knife is used to cut through the seed's tough outer shell, allowing water to enter, and jump-start the germination process.

More important than your hardiness zone, is your 'growing season' - the time between last frost and first frost.
Most winter hardy plants in cold regions actually begin their germination as soon as their internal thermometers detect a warm day. This is usually 4-6 weeks before the last frost. They need this head start so that they can get well established before the first frost of autumn puts them into dormancy.

Any of your seeds that need both cold treatment and stratification, even if they have been cold treated, and manually stratified, at this point probably do not have enough time to establish themselves well enough to take on next winter.

Personally, I would wait until autumn, and I would not scarify them. They need that hard outer shell, slowly breaking down, to protect themselves from cold and moisture until conditions are right.

If you already bought the seeds plant them now and then get some more in fall and plant them again. then the following fall. thin out your plant, selecting the stronger for survival.

Thank John!

I may be mistaken, but I am under the understanding that, what you call "cold-treatment" may also include a process of scarification (called "cold scarification" or "cold moist scarification") , which is combinations of microbial actions and the frost/thaw cycle which both work to breakdown the seed-wall and/or alerts the seed when to germinate.

I planted a sample of seed (about 10% of my stock) this past February in a nursery area to get an idea of germination rates; just this week I got good germination from the seeds planted in February!!! (About 40-50% germination rate; no luck with hawthorn, persimmon, or honey locust but more than half germination success rates, with autumn olive, russian olive, black locust, choke cherry, elderberry, huckleberry, mulberry, ground cherry, silver buffalo berry.)

I want to plant a lot more seed but I'm concerned that if the ones planted in February did not germinate till May, then those planted in May may not germinated till August and they might not make it over winter. I think late this fall, I'll plant all of my seed stock with the understanding that I will not get as good a germination because the seed will be older then.

Thanks to all!

https://www.youtube.com/watch?v=h8LwbH2xHjE

https://www.youtube.com/watch?v=qGH3NHZOV-Y

I may be mistaken, but I am under the understanding that, what you call "cold-treatment" may also include a process of scarification (called "cold scarification" or "cold moist scarification") , which is combinations of microbial actions and the frost/thaw cycle which both work to breakdown the seed-wall and/or alerts the seed when to germinate.

Yes, you are correct. That is how it occurs in nature.

However, if we buy packaged seeds that need this treatment, we must provide both of the techniques manually.
Several month in the 'fridge prior to planting mimics the cold treatment.
Sanding/cutting the outer covering mimics the natural scarification process.
Quite often (especially with hard to germinate seeds), an over night soaking in warm water is done prior to planting.
This warm bath helps soften the coating, and it 'tells' the seed that warmth is just around the corner.

If you obtain your seeds from a reputable seedsman, you should receive fairly detailed instructions for each seed type.

Good luck.

It's not too labor intensive to try googling "elderberry germination" you will find what you need for many species. At the top of the list is
http://www.wildflower.org/plants/result.php?id_plant=SANIC4

which will tell you: "For elderberry seeds to germinate they must be pretreated. Untreated, fall-sown seeds will not germinate until the second year."

USDA sites are good, and often the information source for other sites.
Eg. http://plants.usda.gov/plantguide/pdf/cs_sanic4.pdf
"Without pregermination [stratification] germination may be delayed from 2 to 5 years after planting."

And so forth. Given that they are sweet berries, I suggest part of their natural stratification/scarification needs might include a trip through an animals digestive system then a cold moist period in the soil. Scarification can include an acid treatment, including digestive acids. You get the picture.

Best wishes, you're on to a good project. Keep records! Post your results!
Kathy J