Answer: Scabiosa should be perennial in USDA winter hardiness zones 5 and warmer. It does need a well drained location to survive the winter, however. Wait until spring to fertilize, at that time top dress with compost and/or a general purpose granular fertilizer or a general purpose slow release granular fertilizer. Read and follow the label directions for how much to use. Use an organic mulch about three inches deep year round.
As far as being rootbound, it is important to interrupt that circular root pattern or break open/loosen a densely matted, hardened rootball. If this is not done the roots will continue to grow in a circle and eventually strangle the plant. It seems harsh, but sometimes it is necessary to cut some of them, or slice off a portion of one side of the rootball. Then make sure there is good soil-to root contact when you plant. Water as needed to keep the soil damp like a wrung out sponge, not sopping wet, until the ground freezes. Wait to trim these back until spring, then remove winter damaged stems and foliage. Good luck with your pincushion flowers!
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