The flowers could be considered somewhat pretty—a white or lavender tuft reminding me of cornflowers (aka bachelor’s buttons). The somewhat pretty flowers are probably the only positive aspect of these plants. A common noxious weed, knapweed is the bane of my garden.
The problem is that we live immediately adjacent to an open space, a few supposedly wild acres left by the developer (probably because it’s too steep to build on). There’s Gambel’s oak, six Ponderosa pines, a smattering of yucca, assorted wildflowers, and some rather nasty weeds.