I was thinking of building raised boxes as well. However I live in a cold zone (5b) and I wonder if the plant may "freeze" since the planter is above ground.

@totoro I went for three David Austin climbing roses: Claire Austin, Wollerton Old Hall, and Crown Princess Margareta. Those colors move from cream to a mango color and are fragrant.

So how does that change this discussion?

I live in California, with clay soil. I plant camellias in-ground (using gopher wire baskets, 5 gallon size), but I use a whole bag of an acid potting soil as amendment. I like the EB Stone brand. My roses are all in-ground, and I use the gopher wire cage and a whole bag or nearly whole bag of EB Stone Rose Grow soil. I mix the bagged soil with the native soil. It's working well for me, so far! I do have raised beds, but those are for my veggie garden, and mine are quite high to discourage rabbits. I have hardware cloth (which is not cloth, but a metal material) to keep gophers out along the bottom of the bed. I have spent quite a lot of money on soil. The good news is that now most of the areas I plant in are pretty well amended over the years. I have CA natives in the areas where I'm not growing roses and veggies -- they can survive just fine in the CA clay!

Good luck.

@Deborah Just keep in mind that if you put this acid soil into an in-ground container - the hole in the clay soil - the level of your water table is set by the clay soil, not by the soil amendment. You will get the pH you want from that soil, but you will not get the drainage characteristics of the soil, which may or may not matter for your case. If the water level is six inches below ground level after rain, the water level is going to be six inches under your planting too, and that standing water might be holding back root growth.

The way to get both the pH adjustment and also the different drainage characteristics would be to build a mound on top of the clay soil made from the new soil. That way water drains through that new soil according to its drainage characteristics, and that drainage is not affected by the water table in the clay soil underneath your mound.

“Some own root Austins like acidic fluffy soil Because they are adapted to rainy English weather.”

Although we do have the rainy weather acidic soils are quite unusual in England.

I'm not sure where this focus on acidic soils for roses came from. Like the vast majority of plants, their preferred pH is only slightly acidic (6.5-6.8) because that offers the greatest nutrient availability. I have never heard them being referred to as "acid lovers" and I don't see anything in the literature that points in that direction.

They certainly do not have a need for soil acidity that ericaceous plants do!

I would very carefully try to mix acid loving plants together because sunlight requirements, watering needs, etc may be more crucial for them to thrive. For example, roses require full sun and many camellias prefer morning sun only.

That is going to "force" you to be selective, to not plant any camellia japonicas or reticulatas as their leaves would have a hard time during the summer months. However, camellia sasanquas might be ok in your full sun. Down here in Texas where the summer is so long and harsh, I still put my camellia sasanquas in afternoon/evening shade although some shopping centers put them in full sun in pots. So I suggest you try sasanquas. I am assuming that you get lots of full summer sun in SF Bay though during the summer (ie, it is not often cloudy etc).

I corrected the original post in reference to acidity.

The question I want to address is how high should I make the raised bed. Assume the roses have roots that go down 24 inches. Compare a raised bed that is 12" deep versus 24" deep.

Wastes, what is the rootstock of your Austin roses? The bareroots from the DA website are on Huey but they also sell own root. Maybe you should put in some French drains at the bottom near the clay level if you do a boxed raised bed or make a big mound so the water can run off.

When I was saying acidic vs alkaline, I was referring to slightly off from neutral pH.

I have a 24” raised bed sitting on clay soil with a camellia and several roses in it. The camellia does not do well, but I think that is due to root competition from catmint. The only roses that have done well in that bed are Awakening, Jude the Obscure and First Crush. I have tried other roses, but they don’t thrive. Maybe too much ground covers competing for nutrients. Or maybe because there used to be huge tree in that bed and the dying roots are bad for the roses. Sorry so many factors besides depth of soil and drainage in my situation. I did slope the soil so that rain runs off the raised bed as I was concerned about poor drainage.

Here is an article with some info:

https://homeguides.sfgate.com/can-grow-roses-raised-beds-97477.html

@totoro, I believe David Austin uses Rosa multiflora as its root stock.

Camellias do not prefer morning sun, any that are in flower during frosty periods will instead have a particular need for not being hit by morning sun. Because still frozen camellia flowers hit by direct sun turn brown.

westes, when i inquired they told me Dr. Huey and my roses looked to have that rootstock. It also states this on their website

Own Root Roses

Own root
roses are grown from cuttings and so develop their own root system, as
opposed to our grafted bare root roses which have Dr. Huey as their root
system. Our own bare root plants are very similar in size to those
grafted onto Dr. Huey and meet the same grading standards as grafted
stock.

DavidAustin

I believe the roses from Canadian sources use multiflora.

@vaporvac For the climbing roses I wanted, David Austin told me that bare-rooted plants use Dr Huey as the root stock. Potted plants are using the natural root. I have no idea why they would only use a different root stock on one group of plants.

One will have to call again. The Us website says all their bare root roses are on doctor huy so obviously there's some misunderstanding between their website and what they use if you were told it's multiflora. It would be nice to resolve this issue because most of the country may have issues with multiflora due to its preference for more acidic soil. I live in an area of very basic soil and there's plenty of multi-floor here so I don't know why they always say that. That is strange that they would only use multi-floor for certain roses but who knows.

@vaporvac I stand corrected. The e-mail from David Austin said:

"The Claire Austin is grafted onto Dr. Huey, if you get bare root. The Wollerton Old Hall and Crown Princess Margaretta are both own root, bare roots. All three are own root if you get them potted."

It is easy to get confused by all the different rootstocks used by all the different suppliers! Good thing we don't live in Europe where they use additional different ones! Thanks for clarifying and saving me a phone call tomorrow. I was already wondering if that's why my Munstead Wood was always so chlorotic. Oh well. I guess I'll just have to treat her for that. Thank you for taking the time to look that up. :-)

I had read that Camellias don't like eastern exposure in winter because the early morning sun cause them to thaw and then they freeze up again later in the day.

Indeed, an eastern exposure could damage flowers but, the recommendation does not apply everywhere. It really depends on what type of winter climate one has. In z6, eastern exposure is very helpful and recommended. And probably in some or all z7s. I am in Z8 technically but only a few miles away of where z7b starts. In my mild winters here in Tx and also in north Atlanta, Ga.'s 7b, an eastern planting location was not a problem for the sasanqua and japonica blooms.

Japonica and reticulata blooms do/did well in an eastern location but they do need to be watered deeply before big temperature drops to prevent bud drop. Sasanqua camellia blooms, which typically open in the Fall, are/were not usually affected by early frosts; they too are/were deeply watered when we have/had early frosts associated with large temperature drops. But again, like you said, in cold areas, the blooms need to be protected from winter sun and wind. Hmm, just thinking out load now. I wonder what would one of those very late blooming japonicas do if it was blooming in April and then got a late frost? Blooms not affected much if it is not severe enough? Oh, well, I digress so never mind. ;o)) Ha!