Tuberaria is a genus of about 12 species of annual or perennial plants in the rockrose family Cistaceae, native to western and southern Europe.
 They occur on dry, stony sites, often close to the sea.
Santolina is a genus of plants in the chamomile tribe within the sunflower family, primarily from the western Mediterranean region.
A knot garden is a garden of very formal design in a square frame, consisting of a variety of aromatic plants and culinary herbs including germander, marjoram, thyme, southernwood, lemon balm, hyssop, costmary, acanthus, mallow, chamomile, rosemary, Calendulas, Violas and Santolina.
 Most knot gardens now have edges made from box ("Buxus sempervirens"), whose leaves have a sweet smell when bruised.
 The paths in between are usually laid with fine gravel.
 However, the original designs of knot gardens did not have the low box hedges, and knot gardens with such hedges might more accurately be called parterres.

Question: Are Tuberaria and Santolina both plants?
Answer: yes