We planted a bed with "wildflower" seeds. I'm not sure what to do with the plants once the flowers are spent?
The poppies reached a height of about 4 feet and are now dropping all the petals and leaving what I expect is a seed pod as they fall over. Should I be cutting them back, pulling them, or something else?
Yes, those are seed pods.
If you want this area to become self-sustaining for these annual flowers, then leave them alone until the seed heads dry and drop their seeds. Then cut off the old flowering stems, or pull out the plants if they're in bad shape. Same goes for all the plants in the mix.
You can cut off the spent blooms, depending on type of plant you may get a second set of flowers.
If you want to collect seeds leave the spent blooms on the plants to dry, the poppy seed pods will turn brown and start dropping the seeds so you will need to keep a close watch on those if you want to get any seeds.
If you pull the plants you will have empty spots in your bed.
Just depends on how you want your bed to look.
