I bought 2 bobos in May 2016 (I live in Ottawa, ON zone 5a) I planted one in full sun (6h plus) and the other in part shade (receives only 2h afternoon sun). Both are doing well and growing fine. However, the one in full sun is taller and I guess with less dense bloom than the one in part shade.

I think if you plant them in part shade they will remain compact with more proportionate flower head appearance

This is the first year growing Bobo so my experience is limited.

This is my Bobo in part shade (picture taken today July 20th 2016)

One that I planted in full sun a few months ago looks very much like that with compact and small flower heads. I do think there is something to the way they are initially pruned, but I wonder if there is more to it. The second one I got at the same nursery as the first and the flowers are more extended and conical, yet they were side by side and as I work at that nursery I could see that they got the same amount of sun. The second one also has lighter coloured leaves. The difference happened as I took one home and planted it in my garden and it got more water from the soil, while the other one stayed at the garden centre (till it became 50% off). I have to wonder if the amount of moisture in the soil as they form also affects how dense or spaced the florets are. Certainly the second one I got (at 50% off) would have dried out more being stuck in the pot as opposed to being planted in my clay based soil.

I will take a picture of the other one in full sun and post it tomorrow

Unless one was labled incorrectly, things will probably even out if they are planted in the same environment. You yourself pointed out cultural differences (longer in a pot). They are living things and though not as genetically variable as humans, they do respond to different conditions by growing differently.

That's what keeps gardening interesting.

I did notice with my two new plants (that are planted into the same garden with full sun) that the tallest stems are on those that were left the longest before being pruned so they could branch into two stems. This being done by the grower, not me. Both were purchased from the same nursery side by side within a month this spring/summer, then planted into the same flower bed with the same full sun conditions. Compare where the initial pruning cuts were made by the grower on the first bobo compared to the second and you'll see what I'm talking about. The first two photos are of the one planted first. I suppose I choose it at full price because it was nice and compact.

notice that the initial pruning cuts by the grower are only about 6 inches from the ground and how each stem branches from that point. Every branch has a crotch very low to the ground.

Now the second bobo

It almost looks like it must be a different variety. And now let's see the initial grower pruning cuts from the back of the plant.Notice on the left side of the photo that the very tallest branches come from the one that has the crotch about 10 or 12 inches above the ground compared to the one next to it that branches perhaps 4 inches above the ground. The majority of these branches are much taller at the point where the grower initially pruned them. I think the second from the left was pruned one of the shortest - yet that's the average pruning height on the first pictured bobo. (compare the photos)

So now I'm thinking aabout the real floppy ones I saw at the other nursery. I think that this sort of growers pruning close to the ground to enable multiple blooms was simply not done and that that each of these canes came up as a single straight stem. Then each stem/branch put all it's energy into one bloom head made the stems taller and the flower heads huge and floppy unlike anything in my photos - thank heavens.

So you're saying that the earlier, shorter pruning made for a better performing shrub?

I have several young Bobos that I potted up to hold for a fall planting project- I was worried that I wouldn't be able to find any when I was ready to redo my bed, so bought them early to grow them up myself.

It's the end of July but I think I could get away with a bit of pruning if I get right to it...

In general it seems to me that early in it's life, shorter pruning to encourage low branching rather than individual straight stems makes a better more compact and dense bobo. I think I read in another thread (that I can no longer find :( ) someone saying that that gave it a "stronger framework". Even within that there seems to be some variance. Since both of the ones I bought were side by side at the nursery I worked at, they were likely pruned exactly the same time by the grower, but some branches were pruned higher so branched higher and grew taller. In my opinion the branches that were pruned higher were not as attractive.

For me the blunt pruning cuts were very obvious once I looked for them and noticed two shoots coming shortly above each. The "better" plant had them only 4-6 inches from the base, wheras the other (the second choice, second purchased because it was 50% off) had them higher up, some as much as 14 inches from the ground. Do you have visible flat cuts and forking into two like that close to the ground or are all the branches coming straight from the base with no branching? I guess that would affect my decision to prune or not. Do you have a photo?

Just to say that I'm not an expert on this. I have not actually compared the heavy flowered "floppy" bobos I saw side by side with my dense compact one. To be honest the heavy flowered floppy ones were at an extremely reputable and well run nursery, one I respect far more than the one I work at and so I was stunned to see their bobos flopping. When I want good plants and am willing to pay the bucks, that's the nursery I go to. So I was so stunned I never thought to examine the pruning and branching and I'm not completely sure that pruning is the issue, it's just an idea I seems to make sense from observation of my own. I am throwing around the idea in case others notice the same relationship.

"Do you have visible flat cuts and forking into two like that close to
the ground or are all the branches coming straight from the base with no
branching? I guess that would affect my decision to prune or not. Do
you have a photo?"

No photos- they're out biding their time in my nursery bed.

I'll likely examine them today and decide- will probably prune a couple of stems on each for the best of both worlds if they look like it hasn't been done. Then maybe a light shot of fish emulsion to make it work. [/Tim Gunn]