Sorry I'm so late to the game.... I'll do my best to catch up, I'm sure I'll miss something. Feel free to remind me if I left you out :)
How will cuttings do in sandy soil?
If I wanted to do clusters of trees, would it be beneficial to make 2'x2' weed mats to plant each individual cutting in?
Do the weed mats need to be removed at some point?
What is the best time to harvest Red Osier and HP cuttings?
I wouldn't do anything less than 6' x 6' squares. Weeds will rob all of the moisture and sunlight if they are too small. My preference is to do 6' x 15-20' if you want to do smaller patches. It's a game of edges, don't let the weeds win. I generally don't recommend cuttings on sandy soil.
I'll say, but there are some pitfalls you can run into.
For me deer are a major issue. If you have high DPSM your cuttings must be protected. I've found the only sure fire way is a double electric fence.
Lumite and black plastic will girdle your cuttings after the first growing season. (Hard lesson learned). You have to go back and cut your ground cover material.
Some ground cover, plastics or lumite is a must for weed control.
And some cuttings can't tolerate being planted through black ground cover. Brushpile will have to say which because, I just don't remember as I stick to cuttings that I know will.
Deer WILL eat them if you have very many deer. Usually won't kill them, but they will keep them pruned!
Lumite is a swear word, the charge 2x what everyone else charges! High quality woven ground cover is what you need. (I know lumite is the original term, I bought it in the past too)
Plastic or fabric? It's all about anerobic tolerance. All willows will handle both, most shrubs won't. All hybrids handle both. If in doubt, use fabric. On our site, we clearly explain which ones like what. If you use plastic, cover it with something (anything) or the sun will eat it.
When taking/making cuttings how far back do you go and what are you looking for?
1 year old growth generally is best. I've used lots of 2 year old growth with success. "What are you looking for" is a tough one. I could write a book on that topic. The short answer is 1 or 2 year old growth, never less than 12" long unless you know what you are looking for. 24" is ALWAYS safe. Don't forget the 2/3 in the ground rule.
So lay the plastic early, staple, weight down, and plant 25-30 foot strips. Stuart needs to weigh in here because I'm in a warmer climate and don't know what would happen to plastic at -40. I do know that mine is fine at 10 degrees
I've never had the cold damage plastic, but the sun will eat it in a season. Throw some straw, wood chips, grass clippings or something on it to keep the sun off.
Has anybody experimented with putting cuttings in this time of the year or is it a waste of time?
I've done some fairly extensive fall testing (one year I shipped over 1000 cuttings for free to people all over the country to see how they would do). I don't recommend it. I think it has to do with moisture, but at best I have gotten ~50% success with hybrids. Spring plantings can expect 95%+ success.
Some of these questions can be answered on our blog:
http://blog.bigrocktrees.com/
And detailed info can be found on each cutting on our site:
http://www.bigrocktrees.com/
We have almost 50 types of willows (there are 100's) and several hybrids. Along with a handful of shrubs. I'm only aware of a couple of shrubs that will successfully grow from cuttings that we don't carry (they won't grow in zone 4 where we are located).
I hope that helps!
-John