Perennial Dilemma

We live in a small condo complex in the West End with a planter approximately 12 ft long
and about 18 inches deep. We currently have 3 lonely Boxwoods in it spaced apart. We tried
planting Panda Azaleas in between which promptly died. We need advice on getting some
perennials planted this fall that will flower next year. Any suggestions?

I am attaching a photo of the smaller planter where the Azaleas have survived, but this will
give an idea of the planter setting.

Any ideas of help would be appreciated.

 

Figuring out why the other azaleas failed will be key to knowing what other plants you can get to grow there.

 

We took some branches back to the Garden Centre and he advised us to prune the dead stuff back and they would come back, but they died off. We were careful not to over water, but for me they look diseased. In any case, we persisted, and got new soil and got new Azalea plants from another nursery and they failed too. The boxwoods are fine. We have previously
planted annuals (in the old soil) and they did fine, (geraniums and impatience). It is a mystery.

We now think, we can again put in new soil, but Azaleas are now off the list. We are not gardeners and would like to
have a flowering perennial that has a chance to survive.

Here is another picture.

 

It is often advised that rhododendrons and azaleas not be planted in close proximity to concrete materials, especially older concrete because lime leaches into the soil, raising the pH and negatively affecting the plants' health.

"Planting near concrete foundations or other concrete materials is to be avoided as the concrete creates alkaline conditions (a pH of 6 or above) that are harmful for healthy rhododendron and azalea growth. "
https://www.rhododendron.org/planting.htm

However, you say you got new soil - does that mean you replaced the old soil completely? If the soil is all new, I don't think old concrete would have had time to cause problems.

 

We only replaced the soiled where we planted the second round of Azaleas. Thank you for
the insight on the concrete issue.

Can you suggest something that will flower in the spring/summer that we can plant this fall?
By now you have guessed that we are not gardeners and need help in getting something planted
that will not die. The other residents are insisting on perennials and we need advice on what might
look nice in the that planter.

Many thanks.

 

Since the rest of us aren't able to view the failed plants and the site in person it all depends on you to do the detective work.

 

Could you give people some specs? Which way do the planters face and when do they get sun? Is there something overhead or do they get whatever rain there is? Do you plan to do supplemental watering?
Are you expecting something the same height as the boxwoods? Or how tall?
All the same plant, or how many different things?

I know nothing about this. Do people plant perennials at this time of year?