Not to be semantically confused with: Common Centaury (Centaurium erythraea) nor with similar Centauries such as Seaside Centaury (Centaurium littorale) [plants whose scientific names are similar, but which are in a totally different Family altogether, the Gentian Family (Gentianaceae)].
Easily mistaken for : Common Knapweed (Centaurea nigra) but that has wider lanceolate leaves and is a greyer green. Both have rayed and un-rayed versions, but the rayed version of Lesser Knapweed / Chalk Knapwwed has reddish purple flowers rather than purple the ones of Common Knapweed and looks quite different from Common Knapweed.
Lesser Knapweed / Chalk Knapweed may not exist as a separate entity in its own right, but be one end of a continuous spectrum between two extremes, the other bound being Common Knapweed. For more see Common Knapweed. It is recognised only as Centaurea nigra subsp. nemoralis. Intermediates occur where both Centaurea nigra subsp. nigra (Common Knapweed)and Centaurea nigra subsp. nemoralis grow together. The scientific name is now Centaurea debeauxii.
May Hybridize with : the very rare
Brown Knapweed(Centaurea jacea) if Lesser Knapweed / Chalk Knapweed is the same plant (and is thus highly variable) as Common Knapweed. If it is, then the result is Hybrid Knapweed (Centaurea × gerstlaueri). For details see Common Knapweed.
Not to be confused semantically with : Knotgrasses such as Knotgrass,
Equal-leaved Knotgrass or
Northern Knotgrass which belong to the Dock & Knotweed Family, namely Polygonium [they both have similar names]. Nor should they be confused with Knotweeds such as Giant Knotweed,
Japanese Knotweed or Lesser Knotweed / Chalk Knapweed which also belong to the Dock & Knotweed Family (Polygonium).
Grows in waste places and other rough ground.