Yes they do. You could try creating a microclimate. Black mulch, clear plastic or glass cover. I think you should be ok zonewise, even if you just mulch, if it's a plant that can be mulched. I live in zone 6a, and I only have problems when I try to stretch the zone, and grow things that are only hardy in zone 7 or higher.

But if the plant is only borderline hardy to my zone will macroclimates even help at all? The plant is semiarundinaria fastuosa, a bamboo.

With borderline hardiness it might make a difference, but for hardy plants I tend to think it won't. The freeze line is a good 6-8" deep (where I am anyway), so in reality most plant roots are frozen solid, unless they're quite deep-rooted; even then, the upper portions are frozen. So what difference would a raised bed make - the roots are going to freeze anyway. The key to avoid plant loss is keeping them dormant once they're dormant. Heck, I've stored potted hardy perennials and shrubs in garages and barn, where they are undoubtedly frozen solid in the winter, and I've had minimal losses over something like 20 years.

Short answer - no. Plant hardiness is determined by genetics, not by how it is planted!! A more appropriate issue is if how the plant is growing exposes it to greater temperature swings, which could indeed impact how well it might winter over.

The issue with container plants dealing with winter cold is that their root systems are exposed to the ambient air temperatures surrounding the container/root zone, which can be far colder than frozen soils. This is far less likely to be the case in a raised bed, as there is the presence of a much greater insulating soil mass surrounding them. Unless they are planted immediately adjacent to the edge of the bed, there is no exposure of the root system to the much colder ambient air temps.....and even in that situation, it would only be a portion of the roots that were exposed, not the entire root system.

The advantages of planting in a raised bed is typically improved drainage (often a winter concern) and the fact that raised bed soils tend to warm up faster in spring than does regular ground soil.

To some degree this may depend on where you are located and what you are growing and how high the raised bed is. Around here where we may get a deep soil freeze without snow, but typically get get good snow cover and not really deep freezing when there is snow, it can mean the difference between survival and not for something like garlic which really needs the insulation. if the raised beds are 4”, not much difference, but if they are 2’-4’ and the snow is less than a foot, the beds will freeze. I like raised beds for annual plants such as many veggies, but for anything that has to overwinter here and isn’t dependably hardy, I plant in ground. If drainage is a concern, I try to plant on a slightly raised mound or on a hill where melting snow will drain away rather than puddle.

For my borderline bamboo, it is more a question of whether the above ground parts survive the winter or it gets killed back to the soil or snow line. I don’t know if that is likely the issue for you or not. How well drained is your soil? Would planting on a slight mound be better than a raised bed? Have you considered what adding raised beds over the tree roots will do to the trees?

I don't know, when it comes to bamboo. I'm in 5b/6a. I planted phylostachys nuda, and it did better than well, here for me, but the canes never got higher than 6 ft. tall. I was hoping it would reach 20 ft. I wanted to grow the black bamboo but didn't, because it wasn't as hardy, and as you know, the're very pricey, a bigger than normal plant investlent. Microclimates can make a difference. I have a 4 o:clock plant, that acts like a perennial, because it's right up against a south facing wall. You could try finding another hardier bamboo that's still close to what you're looking for.

I am planning the 3 ft raised bed between ours and our neighbors property so that makes it safer in terms of the bancoo spreading. Second, it will be very close to my neighbors mature red maple so I can't plant it in the ground. The maples will suck the bamboo dry. It's my neighbors maple so I don't care what happens to the tree, heck if it died I'd be very happy. You might say I'm selfish but the neighbor neglects his yard real bad, it's not even a yard..(why I want to make a bamboo hedge to block my neighbors unsightly eyesore wasteland) and they don't even own the property, they're only renting the house. But Yea It's a patch full of weeds. His one giant oak is growing into his shed and bending it severely. It's been like that as long as I have been living here. So you can tell he doesn't give a crap.

We actually have a 1.5 ft raised bed for my phyllostachys aureosulcata right next to my other neighbors Norway maple and that maple is still growing like crazy. So I don't think adding a mound of soil on its roots will harm the tree.

Yeah, my neighbors have a couple trees that I wish would bite the dust. They steal sun from my garden. One is a Pine that seems a little airy, which is better than a heavily foliaged blue spruce, or it's like. The other is a Mulberry which really ticks me off. I don't know a lot about barricading bamboos. There is a bamboo forum here. The P. nuda that I grew spread incredibly fast. The rope like roots would follow the flagstone walkway, but they never traveled underneath it, so maybe the raised bed thing will work out well. I've had a few plants that did go underneath bricks and stones. Trumpet Vine, Campsis radicans, Common Milkweed, Asclepius syriaca, and Empress Tree, Paulownia.

You could alway select a very cold hardy clumping bamboo, like one of the Fargesia species (good to -25F). Otherwise, a raised bed of normal depth will not restrain a running bamboo for long........

I really like Fargesias. Fargesia sp. Rufa gets 10 feet tall and is hardy to zone 5.