This short-lived annual is spread by seed and can mature and produce seed very quickly. It flowers for most of the year and has exploding seed capsules which disperse their contents widely.
It is easily uprooted and should be pulled out before the seeds mature and disperse.
Remove weeds by hand as soon as you see them
Spray with a systemic weedkiller that is absorbed through the leaves of the plant, the active ingredient makes its way through the cells of the plant down to the root. It kills these first and then the foliage starts to die off