| The larvae of P. polonica are sessile parasites living on the roots of various herbs especially those of the perennial knawel growing on the sandy soils of Central Europe and other parts of Eurasia. |
| Perennial knawel plantations were replaced with cereal fields or pastures for raising cattle. |
| In modern Polish, is a word for June, as well as for the Polish cochineal and its host plant, the perennial knawel. |
| I saw no shepherd's purse after December 27th, but knawel was in flower as late as January 18th. |
| Self-pollination allows for distinct races to develop and several sub-species of annual knawel have been recognised, however their status in Ireland has not been investigated. |
