In England the "cottage garden" was less of a style than a utilitarian concept. Carol Chernega, BellaOnline's English Garden editor, explains this well in her article "English Garden History." For a plant to be placed in a cottage garden it must have more than aesthetic value: Historically plants needed to be edible or medicinal to take up valuable space in the cottage garden.
The hardy carnation (Dianathus plumarius) was a staple of the English cottage garden. They were even called cottage pinks. Though many were indeed pink in color, the term refers to the uneven edges of the flowers that look as though they were cut with pinking shears. Hardy carnations are fragrant and edible, having the flavor and scent of cloves. Traditionally they were used in salads, to flavor a liqueur called chartreuse, candied to decorate pastries and dried for potpourri. Hardy carnations are matte-forming plants and work well as ground covers or edging plants. The needle-like foliage can be green, silver or blue. The easiest way to propagate is by division. Unlike the annual floral carnations, cottage pinks are perennials hardy to USDA zone 3.
One common form of bachelor's button grown in gardens today is the blue cornflower (Centaurea montana). The outer petals are blue and the inner petals are purple. A white version with rose inner petals also exists. These are a favorite of beneficial insects such as bees and butterflies. This is one of the few plants that will bloom continuously from early summer until fall. Deadhead the spent flowers and cut back the foliage when it becomes floppy. The foliage will return and there will be a whole new flush of flowers within one to two weeks. Perennial cornflower is hardy to USDA zone 4. The edible species (Centaurea cyanus) also was common in cottage gardens. It is an annual bachelor's button that is started from seed.
The foxglove (Digitalis purpurea) is a staple in an English cottage garden. The tall spires have little bell-shaped flowers up the stems. The species is purple but hybrids are available in white, pink and yellow. Bumblebees can be found inside the florets, and hummingbirds can easily sip the nectar. Foxglove still is used medicinally to make digitalis, a heart medicine. Foxglove is a biennial flower. It is started from seed and forms a clump of leaves the first year. The second year the flower spikes emerge and set seed, repeating the cycle. Once started, foxglove will reseed on its own, creating a nice patch over time.
The pot marigold (Calendula) has a number of uses. The early Romans named the plant calendula, which means calendar, because it bloomed on the first day of each month. The sunny-looking, daisy-like flowers bloom in shades of yellow and orange. The sticky substance among the petals has healing value. It is added to many skin preparations and helps wounds heal. Calendula is an annual plant started from seed in the spring. It will reseed on its own, creating a patch. The seed can be collected in the fall and planted in spring.