The flowers are drawn the way the Voynich illustrator commonly draws flowers from the aster family and that's not surprising if you consider that many aster flowers, like the groundsels, like some species of Petasites, do look like this. The have a cylinder-shaped calyx and a little poof of tiny blossoms at the end and just before they fully bloom those little petals are furled so they look like rounded bumps.
Also, the VMS plants that resemble plants from the silene family have larger bladder-like bumps just behind the part where the petals spread and this characteristic has been captured by the illustrator, as well.
As for Petasites, the roots and the leaves are used medicinally and the leaves are harvested before they get too big and stiff, so one would see leaf scars on the plant as are in the drawing.
Also, the VMS plants that resemble plants from the silene family have larger bladder-like bumps just behind the part where the petals spread and this characteristic has been captured by the illustrator, as well.
As for Petasites, the roots and the leaves are used medicinally and the leaves are harvested before they get too big and stiff, so one would see leaf scars on the plant as are in the drawing.