IMO, at least in my area, hedges just 'happen' once interference (mowing, grazing...) ceases. In my area I expect Crataegus, Prunus, Sambucus, Quercus, Salix, Carpinus, Cornus, Fagus, Rubus, Rosa ... and so on to start showing up soon concerning the woody or rather woody plants. Results vary and of course depend on where you are. But leaving things and not doing a thing is, probably, leading to the most natural results while being the easiest and most sustainable.
I would like to add that personally I value 'naturality' over 'biodiversity'. Many natural habitats are natural monocultures and thete is nothing wrong with nature and no need for man to make 'improvements' here. Take Fagus forests as example. Those are very common in my area and the adaptions making the genus Fagus rather successful is that a) adults shade the area heavily b) they mulch heavily suffocating and further depriving competing plants of light and c) saplings require much less light than many other trees saplings.
In any case the plants listed above might provide a good solid woody basis for a hedge in your climate if you want to speed things up or force it a certain way.

WELCOME!
Yeah it seems that forums aren't as alive as they once were. I suspect many online forum communities have migrated so Facebook groups, reddit, etc.
I just recently joined and am hoping I can still find community on these spaces although I'm anticipating much slower responses. 😅

I had an idea and might try it out. I've read that many acacia species are fire adapted and that the compounds found in smoke will improve germination. I have a electric smoker that is basically set and forget.
I am considering using it to pasteurize some seed starting mix for acacias to help prevent damping off, and also adding smoke compounds to aide in germination.
I guess liquid smoke can also be used to water/mist seedlings of fire adapted species although I'm pretty
sure that it needs to be diluted. Anyone ever try this? If I don't use the smoker I'll use the house oven for plain ol' heat pasteurizatuon, so I really don't see a downside to giving it a try.

Acacia oxycedrus makes a good hedge.

This is my first winter growing acacia. I built a greenhouse this year to overwinter them in.
I'm looking for advice and tips. Do you think I need to heat the greenhouse?
The species I am growing are relatively frost hardy but still small plants in one gallon containers. There are some larger plants which I'm less concerned about surviving.
I am considering using a seedling heat mat directly under the small plants hooked to a temperature controller.
The idea would be to have the controller kick the heat on around 36F and shut off around 40F just to keep the plants above freezing on the nights when it gets down to 15F outside.
I am also considering a small propane heater for if the power goes out.
I'm not sure if hearing is really necessary thought since they will be protected from the wind and rain.
Also how much and often should I water the acacia during winter? I am concerned that if they get too dry the cold could essentially freeze dry then, I've heard that some water can actually help insulate the soil.
Any advice is much appreciated. Thanks

This is one of my favorite posts on the forum. I'm attempting to grow
Acacias in zone 8b and will definitely report on how well they do.
There are several species I'm growing that aren't on the list.

Welcome and congrats on beating cancer. I wanted to respond cause I'm also from the PNW! Glad to see someone else from the region on here!

Hello everyone.
I've been growing Trichocereus for 3-4 years. Recently I've gotten into cultivating Acacias.
I have eight different species so far which I'm testing out in zone 8b here in the PNW.
This year will be the first winter with plants in the ground.
Those plants are two Acacia oxycedrus and two floribunda.
I'm hoping they survive and put on lots of growth come spring.
The rest of my plants are overwintering in a newly constructed greenhouse.
I look forward to sharing my plants and their progress.
 The goal is to get them to maturity and produce seed. 😉
Photo is acacia floribunda and acacia longifolia chillin in the greenhouse.

A lack of property is not necessarily a lack of a garden. I hope you can find a creative option that works for your situations. So many places just begging to be looked after 

Happy to have finally joined, after reading various things on here over the years!  I'm a British academic, although in a completely unrelated area - plants are more of a hobby and mild obsession.

I grow a number of species as houseplants due to lack of a garden, with my most recent successes being two very prolific kanna plants apparently intent on taking over the world, a coffee sapling I've grown from a bean, several Sida cordifolias including one grown hydroponically, two Lagochilus inebrians, and several varieties of coleus.  I also have a collection of seeds, which I am keen to share and swap with like-minded people, hence my signing up here.  I am particularly interested in finding seeds for a particular set of Psychotria, Palicourea and Eumachia species, especially Eumachia frutescens (AKA Hodgkinsonia frutescens) - turns out it's quite challenging to find in the UK!

If you have any questions, just ask!