I would really recommend switching to newspaper. Plastic is not going to harm the soil, but it will block the rain and is suffocating the soil critters.

Back when I was gardening on the East coast, my favorite way of converting grassy/weedy areas into beds was to cut the grass as short as possible, cover the area with newspapers (several layers, overlapping), spray it generously with water, and then pile up chopped leaves on top. That was in Zone 7, so my winters were milder, but by the time I was ready to plant in spring, the grass was mostly dead. But the best part was that earthworms LOVE newspaper and leaves. Every time I uncovered the soil, it looked like a snake pit underneath, and the soil was nice and fluffy from all the tunneling.

In spring I would plant my perennials and spread more newspaper between them, covered with mulch. Just to prevent any surviving roots or seeds from sprouting. By the summer the bed was weed/grass free.

@JoJo (Nevada 9A) Thanks for these tips. That makes sense to cover but allow water. That's what I was worried about with the soil life under this area. I'll find some newspapers today and see if I can set this up with my shredded leaves. Thanks so much for the tips.

Good luck with the roses! And send me some leaves to desert :)

Getting rid of the plastic is a good idea. Also, now is your only opportunity to radically improve the soil, and I would do that ASAP.

First, the holes are doing you no good right now, other than making the work easier in the spring. Your best option is to dig up the whole bed, rather than just holes for the roses. The roots are going to fill the whole area and you want the ground prepared to welcome them.

With a lot of clay soil, now is the time to work in compost and some bagged "aged" or composted manure. Dig it in at least a foot - a foot and a half is better.

The bad news is that this is backbreaking labor, but the good news is that you only have to do it once. Now that I am retired, this is too much for me personally, so I usually find some high school kids that would like to make some cash on a weekend and have them do this for me. Turn the amendments in well. Over the next year and a half the clay will start to break up. Make sure not to step on this soil - ever. You want the air that is now worked in to the ground to stay there.

Once the bed is dug, cover it over with about 6" of shredded leaves, if you have them. If not, get a bale of straw (not hay) from a big box store or garden center and use that. This will insulate any worms that might come by to graze in your newly rich composted bed and encourage them to move in permanently. It will also prevent spring weeds.

In spring, you will be ready to plant. I wish you the best - I just put in a rose bed last year and had my first summer of flowers.

@Richard Brennan Thanks for all of this info Richard. This is what I was initially planning, but the bed is 60x20 ft long....and after all the giant hole digging I got wiped out for a bit. I know I should have added things sooner....hopefully get get on to it the next few days.

Since this area is so big (for me), is there anyway to not have to dig another foot out of the whole area? The other problem with that, which is what I wanted to do, is that this is all on a 45 degree hillside behind a pool. It isn't a retaining wall, but it is somewhat steep. I wanted to amend the whole bed deeply like you said but I don't know how much further I can dig it out without hiring a backhoe to get in there.

Is there any way I can start layering on top...even if the soil isn't fully amended deeply? I was hoping layering shredded leaves, and whatever else on top now, would help jumpstart spring even if the amending isn't as deep as the holes (2x2ft). The compost I can get in bulk is:

"Leaf compost, small amount of limbs and brush. Screened and windrowed for 8 months to 1.5 years. No manure."'

Maybe I could lay that on top and then in the spring when bare roots arrive, mix some in with the native soil for the holes? Eventually it will even out?

Also quick question, I used that same local bulk compost above in my planting holes for last years roses when I planted them, along with about 50-70% native soil. But then I read that leaves are high in magnesium plus some calcium, and that raises the pH of soil plus thicken the soil on-top. Rain releases the calcium and magnesium from the leaves and can harden clay soil.

Do you know if this is true?...makes me worry that I added it in with native soil last spring when planting those roses.

Thanks again for the help. How is your rose bed doing? What types did you try?

Read this before doing all that:

https://s3.wp.wsu.edu/uploads/sites/403/2015/03/soil-amendments-3.pdf

@Embothrium interesting, thanks for sharing. She seems to think that adding top layers is the best way to go, with wood mulch being her preferred top dressing? That is easy enough for me to do each year. Especially since this is a hillside.

RIght up front I'm going to say my post will be intemperate, but in my opinion that article is silly twaddle that doesn't apply to your case (unless I'm very mistaken about your case).

The reason is very simple: for you to have "too much" organic material in those beds would require an ENORMOUS amount of compost, year after year, so much that it's just irrelevant advice. (I'll give a sense of the volumes below in simple numbers). You'd have to try really hard - like ordering in industrial quantities of compost or leaves, repeatedly - to get even close to it being a problem.

Now I don't wish to speak for Richard but think I have an idea where he was coming from. You describe the soil as rocky-clay soil that sounds like it'd been neglected. It's likely fairly dense and compacted with not that much organic material in it, and when you dig it, apart from the top inch or two, not much that feels or looks organic. Tightly packed, not much air in it. (Nothing wrong with that, good starting point - clay soil with organic stuff added - and cheap stuff like leaves - will be excellent eventually).

I _believe_ what Richard is suggesting, particularly since you already dug holes, is amend the soil once and well before you plant perennials. You can get air and organic material in there by mixing or pitchforking and loosen the soil up. You may not need to fully dig this up, mixing around the holes will still be good. It'll still be hard work but it doesn't have to be perfectly homogenous, and you don't have to do it all at once. It might be a lot easier with a rototiller (but don't know about the rocks) - or hire someone for a day or two. Some mix of leaves, compost, a bit of manure if you wish. (if you don't want to dig it in, keep adding mulch every year and let the worms do it for you, just may take many years with compacted clay)

But with this approach you'd really only need to do this once and after that mulch normally (every year is good, 2-4 inches, leaves or wood chips or compost are fine). In fact you don't want to dig it up it every year, only disturb the soil life once to loosen up and then maintain in future years by mulching.

Now the numbers: this is a bit rough and I'm not going to show my work, because can't be bothered to go back and forth to metric (a lot easier in metric).

For a garden bed your size and as described, six inches or so of leaves or compost wouldn't be overdoing it, just as a mulch. Six inches for 60 X 20 ft is about 18 cubic metres (24 cubic yards). That's about TEN full-sized pick-up truck beds. If you're also going to dig some in, you could double that, probably triple it, it's compost, it degrades over time. Depending on climate and other factors, adding four inches of mulch a year (if not too rich) - you could probably do that forever before it was 'too much' compost.

So don't worry about it. Bring in as much compost or mulch as you think reasonable - which for most people is probably as much as they can physically manage or source. Adjust down if you're adding manure or especially fertilizers (this silly 'too much compost' so-called mythbuster is largely just a version of 'too much fertilizers are bad', which is obvious, but the volumes for too much are completely different). Adjust year by year based on results, of course, get a soil test when appropriate.

Sorry small additional point @B - the above wasn't meant to say you have to get dozens of pickup trucks full of leaves or compost. I was pointing out just how very much 'too much' is in terms of sheer volume.

Whatever you can add in terms of mulch, compost, etc., will help - some is better than none, more when you can. Most of the time when you actually spread it on your garden you'll kind of wish you had more (except when actually doing the work). But by no means think you have to get enormous amounts - do what you can, it'll help.

(I expect the exceptions where there is too much are special cases where people add a lot to small garden beds AND supplement with fertilizers or richer organic supplements)

@armoured - Thanks for all of this information, I appreciate it. I don't have a lot of fresh compost right now unfortunately. I do have a lot of shredded leaves and tons of alfalfa hay. I can see if my local place can bring me some bulk compost, which is mainly leaf compost.

They also have shredded wood bark mulch that is pretty shredded and fluffy. I used it on my new rose beds last spring. Gets kind of dense when wet. Would either of those be worth buying in bulk right now....to lay in the big bed with shredded leaves/alfalfa hay?

I don't know if I can dig out a ton more of this bed because it has been cold here now for a few weeks (snow already).....but I can try to get in there and pitchfork as much as I can and lay top layers on the whole thing. I'm assuming the 4 months of winter will help whatever I put on top get into the soil better than just leaving it bare till spring planting. Thank you all for the help with this. Would rather do whatever I can now to help the soil get ready for spring plantings.

@b _zone - no single answer, do what works for you. Shredded leaves and alfalfa hay should be pretty good. Whatever you can add will help, digging in may be a good idea but it's not compulsory (in other words do what you feel you can do). Even just getting a spade in or a pitchfork or pick may help if you can turn and break up the soil a bit, esp if the soil dense and packed.Do this with some organic materials on top and you're working in some of them (whether now or when the weather permits. If you can't work it in, just mulch on top, still better than nothing.

Up to you to decide whether to get in bulk materials, price/effort - to some degree with compost, "quantity has its own quality" (by which I mean volume matters, don't pay a lot for small amounts of magic compost (there's no magic) - large amounts of cheap compost still do the trick). Some places you can get wood chips for free; I don't have an opinion about bark vs leaves or whatever, they're all plain old compost eventually - I'm mostly opportunistic, whatever's available.

There's no shame in doing what you can now with what you have at hand and waiting until you find out what's available locally or have the time or just prefer. It is good to get at least some compost/mulch on the beds before winter, apart from that - well, composting/soil improvement is not a high speed activity, no need to rush.