Clifford is lucky enough to have a motorized chair, except that it doesn't handle being outside too well. It's great for rolling Wragby or even touring the paths, but as soon as he takes it off road, it gets stuck. No four-wheel drive on this baby.
It's not just that the natural world wreaks havoc on Clifford's chair; the chair destroys the flowers. It's like mutually assured destruction, as Connie watches the chair "squash the little yellow cups of the creeping-jenny" and then make "a wake through the forget-me-nots" (13.77).
Lawrence gets pretty explicit as the chair heads off down a hyacinth-covered hill:
"O last of all ships, through the hyacinthian shallows! O pinnace on the last wild waters, sailing in the last voyage of our civilization! Whither, O weird wheeled ship, your slow course steering. Quiet and complacent, Clifford sat at the wheel of adventure: in his old black hat and tweed jacket, motionless and cautious." (13.87)
The contrast between Lawrence's prophetic, poetic prose and the composed, stuffy Clifford is funny, but it also points out how pathetic he is—not even able to steer his own ship. In this passage, the wheelchair seems to become a metaphor for civilization itself, plowing through the hyacinths totally oblivious to the beauty being crushed under its wheels. Al Gore would be proud.
It's appropriate, too, because wheels are strongly associated with civilization. In Europe, at least, civilization depended on wheels—so as far as D.H. Lawrence is concerned, wheels = civilization. And civilization, as we know, = bad. Connie thinks of fate like a wheel, "Wheels that worked one and drove one, and over which one had no real control!" (11.72). Machinery is all wheel-based (think of gears). Really, it's enough to know that Mellors isn't good with machinery to know that wheels are anathema in Lawrence's world.