I couldn't decide what photos to post for 'common' -in the end I decided to go with lavender - which is definitely very common [and much loved in Provence-even sometimes included in herbes de provence cooking mixtures.]
Lavender [genus Lavandula ] is native to the Mediterranean region- though now the plants are planted all over the world.
The name lavender comes from the latin word lavare which means 'to wash' - because the Romans used it to scent water for washing [baths and probably clothes as well].
Lavender flowers are hugely attractive to insects- especially honey bees and butterflies. Lavender honey is delicious -especially nice with greek honey
This is a Painted Lady Vanessa cardui butterfly on lavender - I had never seen a Painted Lady in the UK-but they are remarkably common here.
Painted Ladies are one of the commonest butterflies worldwide, as they are found on every continent except for Antarctica- which is why they are sometimes known as the Cosmopolitan butterfly.
Lavender sachets are still used to scent linens as they deter clothes moths and, of course, the essential oil is widely used in modern aromatherapy- as a general anti infection agent
Lavender was used as an anti plague meaure in the Middle Ages and its now known that lavender also repels fleas.
It is also very good for killing and deterring headlice and nits in conjunction with olive oil -much better than chemical potions, as the bugs are often resistant to modern insecticides.