Old English and German folk traditions used calendula in love charms, specifically the ‘keep a relationship honest and loyal’ kind. Brides would carry it to ensure faithfulness, which tells you a lot about how this plant was understood in folk lore and by witches at the time.
Medieval churches decorated altars with calendula as an offering to the Virgin Mary because it was considered a flower of devotion and constancy (yet we still have to ask if we can be Christian witches). The plant has a layer of commitment magic that gets skipped when people go straight to prosperity and court work.
Try adding it to a handfasting sachet or anniversary ritual sometime. The warmth it brings to partnership workings is impressive.