griffon said:

What are some good groundcovers to plant above tulips, big floppy
crocus, etc? Some of the groundcovers I have tried just didn't work
too well, they were too aggressive. There are a few areas where I
have a lot of bulbs for spring but really there is nothing there after
the bulbs stop blooming.

Late emerging perennials (depending on the sun exposure) -- ones
that die back completely (leaving no rosette of leaves) and emerge
slowly when the weather improves.

Hostas can work in areas that are shaded by trees in summer.
Ceratostigma plumbaginoides (leadwort, 'hardy plumbago') might work
in those areas, too. This one does like to spread around a bit, but
isn't so agressive that the bulbs can't come up through it.

For sunnier areas late-emergers like balloon flower (and butterfly weed
(Asclepias tuberosa) might fit the bill.

Or, you might consider woody flowering plants that get cut back hard every
year (like Buddleia or Caryopteris).

And don't forget annual bedding plants! Start some later than normal and
set them out as the bulb foliage ripens. (I'm partial to dwarf Cosmos and
various types of Salvia as they don't seem to get eaten up by bunnies and
earwigs.)
--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)