Honestly, no. But I have very sandy soil, amended on top with rich compost each year (and each time I transplant something), so I never see the point. Often my soil is more friable than the potting soil things come in, though bereft of nutrients.

If I had regular soil or more clay in my mix, I would cut at least a 12" x 12" cube.

I can honestly say I have never measured. I think the size of the hole is relative to the size of the clematis. I go for depth that it needs to be planted at & however wide the hole gets to get that deep is how wide it ends up.

I have pretty good clay soil that has been gardened in for decades so not a real concern for me.

Yep, big / huge hole digger here ... sometimes up to 30 x 30 inches. For the most part, I have good soil, I dig most of the stuff out and spade down deeply into the bottom of the hole and lift out any big clumps of clay, sometimes it's friable and I don't have to remove much of anything and just incorporate a good amount of peat moss. I dig deeply and amend for almost all my plantings ...

Terry

I don't dig deeply or amend for most of my plantings. We've topdressed with compost every year for over a decade. However, I do plant Clematis deeper and I'm beginning to think not spending more time on their holes is the reason why some are not doing as well as others.

The Clematis planted in a bed next to the house that was heavily amended and rototilled more than once and dug deep because of setting the trellis posts two feet deep have thrived a lot better than Clems in other areas that were just stuck in holes even though the ones just stuck get more sun.

The Clematis planted where there are tree roots from neighbor's Douglas Fir trees and Arborvitaes do the worst. They just struggle along.

I have no way of knowing if it is variety or soil conditions as I don't have any duplicates and most of the stragglers are Type IIs that weren't properly pruned to begin with and some were half dead when I brought them home too "rescues".

I don't believe I have ever dug a hole 24" x 24". I'm usually trying to shoehorn a clem in SOMEWHERE, and don't want to dig up adjacent plants. Most of mine do fine.

I have a lot of clay soil here and I never measure either. Mostly I am happy to dig it as deep as I can which is usually not more than about 16 inches deep before I run into hard pan clay. I would need a blast of dynamite to get it deeper! So I just go for as deep as I can. Usually I can get the 24 inch width, but not much depth, and the clems do ok.

Interesting how each of us approach digging a hole differently yet we all still have a modicum of success. I had to laugh when twrosz mentioned that she digs 30x30" holes. All the more to you twrosz. I would not have the strength nor the stamina for that. When first starting my bed I had it dug 24" deep by someone else, however, now that I am doing it solo in other areas of the property I am going down about 16" and 20" wide. Time will tell. I too have hard clay so I add lots of goodies to the soil. Thanks everyone for your feedback.

"I had to laugh when twrosz mentioned that she digs 30x30" holes" ... he, is me ... lol

If I don't break into a sweat and am somewhat pooped out after digging a planting hole, then I know I have not given my all, lol. Clematis love having a deep moist and friable root run. For the most part, I can dig down rather easily into the chalky soil, the subsoil is often a sandy friable clay that breaks up easily. I really don't like digging such large holes, though I know I'm giving them the best home I can for the long term ... that saying comes to mind, a hundred dollar hole for a ten dollar plant, or something like that, lol. I get very good results for my efforts!

Terry

Since I'm planting my most recent clematis in pre-existing gardens where the old soil was either removed fairly deep, or in terraces which were filled in, I only dig a big enough hole to fit the roots in. Since they are being planted in gardens with deep, loose, fantastic soil created from mostly well rotted manure, it's like having a very large hole.
Almost all the clematis take off.