It's not a good idea. Mine gets lots of sun, but far less heat. Abundant brown "flowers."

I disagree. PeeGee hydrangeas are the most sun, heat and drought tolerant of any hydrangea species. They are rated to AHS heat zone 9, which translates to 120+ days over 86F. This plant grows in very diverse climates, including Texas, which is notorious for having extended, very hot summers. In my nursery setting, these plants are out in full sun all summer, on the gravel or asphalt and in their black nursery cans - the temp at times easily hits the 100 mark, especially this past summer. The plants are fine and bloom beautifully. As long as you can provide sufficient water, especially during its period of establishment, I would give it a try.

Hmmm... well thanks for the responses, but I'm still not convinced.

I just looked up AHS heat zones and it looks like I am in zone 8. What does "rated to zone 9" mean? It will "survive" zone 9? I'm pretty sure it will "survive" if I give it enough water, but I'm looking for more than "survival". PNW zone 8 I'm guessing is Willamette Valley or Puget Sound? I've lived in both of those places and the sun here is far more intense.

Still it might be worth a try, if it doesn't work out to my satisfaction I'll just take it out and re-plant with something else.

I have never seen paniculatas here in Texas, gardengal48. Have always thought how odd and do not know why. No one at nurseries can explain that to me. But one nursery last year ordered a few Limelights. First time in 32 years that I have seen a paniculata for sale at a local nursery. I do not know what to make of it so I have hesitated when wanting to order them by mail order.

Heavens!! No one was trying to twist your arm....only to let you know that it is possible to grow these in your location. FWIW, there's lots of places in the US where it hits above 100F in summer and these hydrangeas are extremely common across the country. If you don't want to risk it, don't grow it.

Comparison of heat zones to USDA hardiness zones are really meaningless - one has nothing to do with the other. They should be used together as a guide (only) as to what should be able to grow successfully in your locations. If PeeGee hydrangeas are listed to heat zone 9, that means they will grow where they receive as much as 120-150 days of temperatures above 86F.

Luis, I don't have an answer for you but I do have a theory :-) In areas that have mild winter climates, like zone 8 and above, the focus by nurseries seems to have been on those hydrangeas that are best suited to quite mild climates - macrophyllas, asperas, serratas, etc. Arguably, these species tend to be less sun and heat tolerant than do the paniculatas, yet you see them sold frequently in very hot climates - Texas, SoCal, the southeast. Until just recently, when all the new cultivars began flooding the market, you couldn't find paniculatas in my area either. Now they are sold as frequently as other, less cold hardy species.

Don't worry... you are not twisting my arm, in the end I am going to do what I want. I just like to hear other people's experiences, these forums are a great place to find such information.

I understand heat zones vs hardiness zones, was not trying to compare the two. I looked at your "PNW zone 8" info and figured that must be Willamette Valley or Puget Sound. I was comparing those areas to Boise.

To me, the heat zone system is not really a good measure of summer heat intensity. The number of days above 86 has little to do with how hot it is at the peak of summer.

True that PG hydrangeas are the most tolerant of sun/heat/drought tolerant of the hydrangeas, but not as much as other ornamentals that would be suitable for the OP's conditions.