Sorry :) I'm located in Indianapolis (Indiana). I'm not sure if these would be garden hybrids or not. I do know that these shrubs are at least 50 years old, if not more. Our house was built in 1918, so there's a pretty big time frame in which they may have been planted. It's okay if I don't get it down to the species level. I just wanted a confirmation on if it was actually Philadelphus or not simply so I could find out the proper pruning methods for them. I like them a lot so I have no plans in ever chopping them down, but I would like to be able to cut some of the dead away so they aren't quite as barren throughout the summer after the blooms have died. I figure that pruning them should help to sprout new growth and fill in the bare areas where all you see is the wood in the center.

Thank you for your thoughts. I had never seen a MO until I moved into this house. I took branches from the shrub and a picture of the one flower from last year, which was on the top of the bush, to the county extension office and to a nearby nursery. You should have seen me getting the picture, leaning out of the 2nd floor master bath window, holding a 300mm zoom lens camera way over to the side... The neighbors do remember the bushes flowering years ago and both afore mentioned sources identified them as MO. And you are correct- my husband says I overstated the height of the bushes by some 5'. OOPS! So, I am quite convinced that we do have MO of some variety. I lopped them all down to ground level on Sunday, watered deeply, and today have 2-4 new shoots on each bush.

Rainfall probably inadequate. Amending of planting hole backfill undesirable, it affects how water moves into and out of planting holes so treated. Under dry conditions an unamended soil will often have a greater attraction for water than the coarser textured amended backfill, resulting in chronic dryness within the planting hole. For the same reason intact potting soil rootballs are apt to shed water to surrounding soil. You have to water so as to make up for this until newly planted stock roots into the unmodified soil beyond the potting soil rootball. If the planting hole backfill has been amended the plants may have to get into the unaltered soil beyond the planting hole before they are out of danger. Plants sufficiently damaged by poor moisture conditions within the amended planting hole may be slow to root out of it, or even die. Otherwise rooting into natural soil beyond planting hole often quick - within the first year after planting - after which top growth picks up nicely, creating the false impression that amending of the planting hole backfill produced a good result. Rocks cool the soil the same as organic mulch, it is the shading that is the main benefit as far as improving moisture conditions within the soil is concerned.

They bloom on last year's growth, so one has to kind of watch lopping off too much if you want it to flower. I used to think it bloomed "on old wood", until I actually looked the info up yesterday. I usually end up pruning mine back every other year (not down to the ground tho, it's way too high even if I wanted to do that,which I don't) and have discovered that it doesn't like to have the ends of it's branches simply trimmed off - much of the branch will die back if you do that.