Don't set fire to it!
Be gentle, wait until the long brushes start to fall over, this happens all year round, then, just pull them out of the plant. Leave the straight, healthy ones. The 'flowers' or brushes only really seem to die off during winter, but as soon as the frost stops, they seem to start growing again, so just keep removing the ones that fall over and if you want to stop it getting really big, use some gloves to remove the dead and lower green grassy parts at the bottom.