Two things:
You never plant IN compost.
and
Earthworms turn the mushrooms into compost. The purpose of compost is to feed micro-organisms in the soil who in turn poop out what you really want to feed your roses. Whoever got us thinking that we were feeding the roses when we added compost was just trying to make it simpler than it really is.

It is aged manure, which has been partly depleted of nutrients by cropping the mushrooms, and which may or may not have a whole lot of lime added to control mushroom diseases. Check the pH before using. If pH is not an issue, it is fine as a source of organic matter. It is not soil, not a planting medium. Plant roses in amended mineral soil,

Well, Michael, you are far more knowledgeable than I; as a matter of fact, I consider you to be my gardening oracle. However, I've been planting in horse manure that's composted down to almost a black dirt, then mixing in kitty litter. I've been doing this for around 15 years. I let it settle down for weeks and then the top two feet or so I fill with potting soil mixed with kitty litter, then let that settle. My reason for doing this is nematodes. So far, I have had no problems that I'm aware of.

I learned the hard way to prepare the holes way in advance when you're totally replacing soil, otherwise the soil settles and your rose is sitting in a depression. I amend the entire bed, but not to the depth of the rose holes.

What is supposed to happen, Mike, if you plant in compost? I've been getting away with it so long, it never occurred to me it could cause a problem. What would be the difference in this and lasagna gardening where you're planting in layers of compost?

Well, the kitty litter part of your formula is mineral. And in lasagna gardening, you set the plants in the mineral soil and they put feeder roots up into the compost layers. This is just an exaggeration of what happens in nature where fallen leaves and dead grasses are constantly rotting into an organic surface layer.

People do successfully grow roses in deep holes filled with organic matter, but all-organic matter is not optimum soil. Why not?
--massive shrinkage over time, as bacteria literally eat the soil. You seen pictures from the Everglades where 6' of muck soil have been lost during the decades of drainage and cultivation.
--nasty anaerobic decay of deep organic layers.
--poor drainage of deep organic layers after they rot to fine muck.
--failure to retain phosphorus as normal soils do (but addition of kitty litter would cure that).

Thank you, Michael. Do bacteria still continue to eat the manure considering how much I have composted it before pitting it in the planting holes? Also, would poor drainage be an issue considering it's surrounded by sugar sand?

I guess I will start adding back in some native "soil" into my plantng holes to see if I can tell a difference.

A layer of heavy soil above a layer of sand or gravel will develop a non-draining zone at the bottom because the capillary attraction within the heavy soil is stronger than gravity, and capillary attraction within the sand is very weak. This is called a "perched water table" if you want to look it up. Horticultural scientists recommend a relatively uniform, non-layered soil.

However, if your native soil is pure sand, you will obviously need to create some layering. A perched water table say 16" down if not going to bother the roses susbstantially.

Yes, Michael, thank you. And thank you Landlady and Floridarosez9.
I'm getting a good education on this forum!

Michael, is there a way to estimate how deep an own root rose bush's roots will grow? And will the roots grow as wide as the bush itself?

They do grow good veggies in Florida muck - celerY for one. My beds never puddle amazingly even with our drenching rain. Floridarosez, glad to hear how long you've been doing this
it doesn't make sense to a lot of people. I started adding topsoil after Michael said some years ago that minerals were needed. Trouble is some bagged topsoil iS just sand. Don't need more of that.

Sherry

Here is a link that might be useful: If only sweat were irrigation

Own root roses all have different rooting habits. Some will make a tap root, some won't. Roots of Fortuniana rarely go deeper than 16"even for old plants. With almost all roses, a majority of the fine feeder roots will be near the surface, less than 10". I have some roses in a bed with only 16" soil depth over a gravel base, and they grow very well.

Okay, here's the deal, if anyone in Florida is still following this thread. I dug up a rose that was planted in the last year using the above method. The only thing different was that the kitty litter was only at the bottom of the hole instead of mixed in (my husband couldn't be bothered and I wasn't home to supervise). The stuff in the hole looked like dense, dark dirt with white sand mixed in. It was loaded with the largest, wiggliest earthworms I've ever seen. There was no sand mixed in at the time the composted manure and kitty litter were put in the hole, so I can't account for the white-looking stuff. When I picked up a handful it was moist and crumbly. I found no layers of excessively soggy, rotting or mucky areas. Is it possible earthworms and other bug activity pulled small quantities of native sand into the manure and that accounts for the white sandy stuff in the hole?

When I replanted the rose, I mixed kitty litter into what came out of the hole and put it back in the hole.

floridarosez9,
that's great news! I have a question for you. If you were to have an own root rose in a depression, would it hurt to just add more potting soil?

I have done that before with no problems. However, I could see that if you piled it too thickly around the canes, you could feasibly rot the canes.

I thought the canes might root.
By the way, what kind of potting soil are you using with your kitty litter?

I suppose if the soil you placed around the canes was light enough, they might root. I actually use the cheapest potting MIX I can find and mix with the kitty litter. Potting mix is lighter than actual soil.

Good to know. Thanks for the info!

G-in-f, I just reread my previous post about the depth I start using the potting mix. I stated top two feet, but I measured, and it's less than a foot. It only seems like two feet when you're trying to fill up that hole. It takes a lot more than you think it will.

So you know that your roses roots grew down below the potting mix and have been living in pure composted horse manure and kitty litter for years (plus whatever sand the earthworms carried in).

Wouldn't it be a great thing if someone compiled the practices and results of a couple dozen florida growers of own root roses? There are tons of books out there, but nothing for Florida people doing own root.
If I were 30 years younger, I'd start a virus indexed OGR on fortuniana nursery. Then we could thumb our noses at those nasty little nematodes and mosaic leaves.

Thank you for clarifying the depth of your potting soil. I have dumped 6 - 7 bags of Jungle growth in a couple holes, and I understand when you say "it feels like two feet when you're trying to fill up that hole".

Cheers!

Oh, what I wouldn't give for a local nursery that grafted onto Fortuniana. We could get away with minimal amendment of the soil then, not to mention our bushes would get huge.

Question, when you say 'kitty litter' are you talking about the clay stuff or the other absorbent stuff? Better yet, a brand for an example would be informational.

The cheapest generic pure clay you can buy--no scent granules, no baking soda, no absorption crystals. I use Special Kitty.

I forgot to say you can buy it at Walmart.