Wow, you have a lot of questions that I have been wondering about too. Several years ago I divided a hosta that was growing slowly. I put it in a pot with good media and put it in some sun. It began to grow into a beautiful hosta. I was so surprised. (This is similar to your plantaginea.)

I have lots of tree roots on my property. So I have been growing many of my hosta in pots and I have hosta in spin out bags in the ground. I find it a lot of work! So, I too, am thinking about raised beds. My husband says that water drainage must be taken into account when building these beds.

I am wondering what size pot you have your largest hostas in? My largest hostas in pots are Striptease and Guacamole and they are four and five years old.

Sorry I can't help you with the raised bed questions.

Mine are not really large yet. Several that are in pots have been bought in the last 1 - 2 years including Elegans and Royal Standard. I have Elegans in a 7" wide pot and RS in an 8" wide. Patriot and Sugar and Cream were still in the 1 gallon nursery pots all last winter and were planted in the ground in about mid-spring. Out of 3 Patriots, I have had 1 new leaf. Unfortunately, I found out this summer that Minuteman would have been a better choice for this area. Sugar and Cream did a little better with 4 new leaves. So they're obviously are sleeping - hoping for creeping next year.

I'm disappointed that the Guac division I put (in a 14" pot) has not grown as radically as Plantaginea. But maybe it's bcs it was doing well where it was before. I had to divide the plant in the ground bcs it had become too large for it's area. I can't remember when I did it - sometime in the last year or 18 months. It has made 2 new plants so that's good.

Maybe somebody will come along and answer our questions. Might take a couple of days.

The main problem is the tree roots grow into the raised beds eventually.

I've been looking and looking for an older post I saw about raised beds and tree roots. Someone asked if you couldn't put "spin out" fabric or bags underneath the raised beds. Unfortunately, her question was not answered but I saw lots of posts abt how well the bags work for planting the hostas in the ground. Of course, you have to be able to dig the hole! I think I will start that as a new thread so more people will see it and link to this thread.

newhostalady, I've really combed thru some older threads (you were in some of them) and come to the conclusion that as zcathy said, the tree roots will eventually grow up into them. So, unless I get a positive answer on laying the spin out fabric underneath the beds (my other post), I am considering using spin out bags inside the raised bed. Extra expense but if I don't have raised beds in the next few years, I may not be gardening after that.

One of the older posts discussed that the large spin out bags are too tall and also too narrow for hostas. So someone cut up 2 of them and sewed them together to make a wider and shallower bag. I can't sew but maybe I could take it to a seamstress - more expense. I think it's in this thread.

http://forums.gardenweb.com/discussions/2005366/spin-out-bags

Of course putting them in bags, even wider ones, is going to limit the size of some of them which was something I didn't want to do, but I guess I have to give up on a full size mature plant (say Royal Standard, reputedly 5' wide at maturity).

The jury seems to still be out on planting mix and it's not one size fits all any way, as I'm sure you know. Barring any new input, I think i am going to do 1/3 vermiculite, 1/3 compost and manure (3 different kinds - Black Kow, Moo-Nure and homemade) and 1/3 bagged garden soil. There are so many "formulas" out there, I just decided to pull from here and there and make my own.

Well, it just occurred to me that using the bags might necessitate a certain planting mix. Aaaargh, the research never ends!!!

Before I bought a roll of TexR spinout I glued (fabric glue) two bags together and it worked fine. Probably any glue would work as the pressure of the soil in the bag would hold the bags together.

newhostalady, after having the big bed built on the sunny side of the yard, there is still some wood left. If I cobble it all together and buy a piece or two, I can have another bed. So, I'm going to do a hosta bed after all! I decided to just go for it and not worry abt some of the possible problems - just do what I can do abt them.

I had not wanted to use my good wood to put a bottom on the bed (per your suggestion of a bed raised off the ground) but I was given a couple of pallets and will use that wood for the bottom. I'm not going to raise it off the ground tho. So the tree roots may invade thru the cracks and the bottom will eventually rot away, but maybe the hostas will be well established by then and not be so affected.

Myrle ( McTavish) has raised beds all over her yard and they do just wonderfully and grow bigger and more healthy then pots She may have pictures of them somewhere in this site if anyone knows where. With water I don't think it matters what soil is used. If worried about tree roots put a mesh in the bottom before adding the soil. When we helped put in Myrle's we never put in a bottom and they are just fine now 3 yrs later

Almosthooked, That is good to hear! I would love to see those pics. Do you know her user name? If I had that, I could search it and maybe find the pics.

The site may be under "stumps in the garden" and her username is McTavish, The posting is April 5th, 2016 by Ken_ Adrian. Not sure if I tag you on that site but that may work too. We are neighbors and she is such a pro and has taught me so much as far as hosta and great ideas

I just started a raised bed for hostas. We have hard, clay soil here. I added a layer of soil pep (which is like refined bark), a layer of peat, and a layer of organic garden soil. My raised bed is probably 16-18" deep. I expect the hostas to enjoy their new home.

Popmama, very nice! Tell me more abt the layering and it's purpose, please, especially the peat And is yours dug into the ground or is the rock border itself 16 - 18" high?

Ken and almost hooked, those people could charge admission to their gardens!

First yard,

The rock border is 16" tall. I removed the grass in the area, then dug a small trench in the shape of the bed. I lined the trench with large cobblestones I had from elsewhere in my yard because I knew those would not be seen. Then filled in the trench rocks with sand. After that, I started building up the rock wall to about 16". From there, I filled the bed with the soil pep, then peat, then garden soil. I just used peat because I have used that in my other raised beds. I didn't really bother to mix the three different mediums. I just layered them. I figure, over time the dirt will settle and it will all mix itself over time. The three layers are deep enough to make planting easy and hopefully allow the roots a nice, soft place to start before they hit the clay soil below the former grass line.

I'll send updates in the Spring.