Thanks to the folks on Name that Plant, I think I've got an ID... they said Mock Orange, and when I just now went down to the park, I found this seedpod:

{{gwi:272177}}

which I think confirms the ID. Does anyone have experience with rejuvenation pruning for these? They are old and overgrown and haven't had care or pruning for years -- tons of woody growth and sparse foliage. And obviously (since this was the only seed pod I could find on four large bushes), they aren't blooming much, either. What's the best approach to trying to restore them?

rejuvenation should be done in stages over the next 3 growing seasons. Take only 1/4 to 1/3 of the largest old growth per year from the plant......doing this will encourage new fresh growth without shocking the shrub and putting undue stress on it......
In 3 to 4 seasons you will have a completely renovated and viable flowering Mockorange. It wouldn't hurt also to amend the soil with compost and give it sufficient water to help it along.

Ian

In my opinion and experience, the 1/3 a year process is not necessary with mock oranges. I have cut two old, rangy plants to the ground and almost immediately they had full, bushy growth starting from ground level. These things, like forsythia, are indestructible. One thing to consider this late in the season in zone 5 is waiting until late winter, early spring to do it...but frankly I would not be nervous about doing it now (see above about indestructibility!).

Since I have done it, I agree with simcan, especially about the spring pruning vs. doing it now. But, ians' method does allow continual bloom that would be lost for at least a year if the plant was totally cut to the ground, and certainly less shock to the plant.
hortster