Hello, I have a pink diamond tree also. I planted it either in 05 or 06 also. It is my only hydrangea tree and is about 6.5-7 feet tall. I am far from an expert but I will chip in my 2 cents. Either early spring or fall would be my best guess in when to transplant it. Hopefully someone else can tell you which of the two times would be the best. I try to never transplant shrubs/trees unless I absolutely have to. I bought mine from a local nursery and was in something like an 8 gallon pot or bigger. No real noticeable height has been gained either for me which is fine for me. Maybe has gained a foot or so at best across the years and mostly I would say from the head of it. I think once they train it to be a single lead and cut it to branch out. I dont think the trunk of the tree will get much taller in maturity. Only the head will continue to get taller/wider, but i think is limited by being a single lead in tree form. I think it would take a long time to train a single lead to be 10 feet or more tall and the growers want to cash out long before that...lol. But again I am no expert in it and I am happy with the height of mine in my situation. I see many people around my area with limelight trees that flop and need staked and seem to not like being in tree form. The pink diamond has never needed staked and seems like a very sturdy grower in tree form. Havent got to see a quickfire in tree form, but have them in shrub form. How fast they grow and well branched, my guess would be they will be another winner in tree form.

heyruthie - cut a dried flower head from the plant and put it a zip-lok bag. Shake vigorously for a while, then tip the zip-lok so all the stuff slides down ito a corner. The fine dust will be the seed. Remove the flower head and all the large debris, and scatter the seed on top of a prepared starting medium, water, keep warm, and germination usually occurs in 7-10 days.

I planted a pink diamond hydrangea in full sun in late march. The plant was already five feet high in a tree form. It began to leaf out at the same time as my two mature macrophylla hydrangeas. It is nicely branched, full and abundantly leafed. It began forming flowers, abundantly, in mid june, forming pure white 8-10 long panicles. It weathered the drought conditions we experienced all through June and July here in Philadelphia. I kept it watered. No withering or ill effects were noticed. Now in early August, the panicles are glowing a soft pink as promised. To say the least, I am very, very happy with this plant. I understand it blooms on new wood so I will do some research on how best to prune. One site said prune until you think you've killed it and then prune some more. I won't go that far but will give it a hair cut in spring, well before it sets flower buds in June. It is a lovely thing.

I know this is a very old thread but I found it searching for info about a pink diamond I just bought. It's been sitting in my front yard waiting for landscapers. Thankfully, I had time to observe it. It is covered with flies, wasps, hornets, and all kinds of zipping and buzzing insects by the hundreds. I drove around looking for others and sure enough they were all buzzing with insects. Now, I plant beds for pollinators. I garden organically- no herbicides/pesticides- not even on my lawn. I fully support the philosophy that all life matters. I wouldn't use anything that would kill the little buzzards. They're only doing their jobs. But this tree scared my kids and I had planned to use it for some shade near a future gazebo. I know that it will make my guests uncomfortable in the location I had planned for it. This is not a hydrangea for anyone who will be bothered (or terrified) by buzzing insects with the potential to deliver quite a sting. Sadly, I decided to return it. Just wanted to share this experience so another person didn't make the same mistake. Now, I'm on the hunt for a very small, non-flowering tree to beautify my landscape. :)