Many of the popular and old-fashioned flowers we grow are neither annuals nor perennials. They are biennials, which are plants that require two growing seasons to complete their life cycle. It is confusing because some biennials are grown and treated as annuals and some are actually short-term perennials. In the first season, the plants germinate and produce a mound of foliage called a rosette, which is a circular cluster of leaves just above the ground. In the second season, the plants send up a flower stalk and after it flowers and produces seeds it dies. Some plants grow quickly enough that they can be sown in early spring and still bloom that year.
English daisies are short plants (6"-8") and make a good edging plant in full sun. They grow wild in England where there is cool soil and moist air. They do best here in the cool spring and don't bloom much after June .
One of the most well-known plants grown as a biennial is the pansy or viola. Actually, pansies are short-lived tender perennials with fibrous roots, but they are treated as biennials. In milder climates, they are planted in the fall to bloom in the spring. These cool weather, but sun loving plants stop blooming when night temperatures consistently rise above 60 degrees.
If you would like a dainty true blue flower to bloom at about 6 to 9 inches among your spring bulbs, the forget-me-not (Myosotis) is a great choice. It grows best in half-day sun and moist soil where it will eventually form a carpet if you plant it two years in a row and allow it to self-sow. Unwanted plants are very easy to pull out. The Chinese forget-me-not (Cynoglossom 'Firmament') is a rather coarse plant with bright blue flower racemes that grows to 18" in sunny locations.
Sweet William (Dianthus barbatus) is one of the oldest known garden flowers. There are many other Dianthus (Pinks), which are either annual or perennial, but Sweet William is a biennial. Full size varieties have several stalks growing 10 to 20 inches with rounded flower clusters of white, bright red or pink. Other varieties are dwarf, growing 6 to 9 inches tall with a spread up to 12 inches.
Iceland Poppy and Stock are two cool weather plants that are biennial. Iceland Poppy has 1-foot flower stems with dainty clear soft colors. Stocks are a very fragrant flower that is used often for cut flowers. It has spikes to two ½ feet with single or double flowers and soft grey foliage.
Foxglove (Digitalis) is a tall biennial that is one of gardenings old favorites even though on most varieties the bloom faces one side. They grow in partial sun to light shade and are not long-lived, but they do self-seed. The standard varieties are straight and stiff-stemmed, climbing to 4 or 5 feet. The variety 'Foxy' is shorter, at 3 feet. You may cut off the spent stems to get a second blooming.
Canterbury bells (Campanula) is a truly beautiful and unique flower. It got its name because of the 2-inch long bells that resembled the bells rung by pilgrims on route to visit the tomb of Thomas A. Becket at Canterbury, England. Some have cup and saucer like flowers and others have double blooms. They grow from one to 4 feet tall in June in shades of blue, pink and white.
Most of our grandparents grew hollyhocks and the older varieties could reach up to 12 feet tall. Most varieties grown now are between 2 and 9 feet tall and bear 3- to 5-inch double or single blooms in white, pink, rose red, yellow or purple. Plant them two-feet or more apart to give them good air circulation to help prevent the rust that they are prone to-. They like full sun to part shade and should be sited at the back of a border or along fences and walls. They may need staking. These are not long-lived plants, but they do self-seed and the seedlings may be transplanted in the spring. Annual hollyhocks are also available.
If you want a bold pyramidal form at 3 to 6 feet tall, you might consider Verbascum. It blooms in early to late summer in predominantly yellow, red or purple with velvety textured foliage. It is drought resistant, but can become weedy with self-seeding.
Other biennials include Wallflowers (Cherianthus), Salvia sclarea (Clary Sage), Lavatera arborea (tree mallow), Malva sylvestris, Oenothera (evening primrose), and Silene (Catchfly).
If you buy plants or biennials at the nursery, you will have flowers the first season. If you plant seeds, it will take two seasons. Start the seeds of true biennials in cell packs in early summer and plant them out in a nursery bed in September. Mulch the rosettes after a hard frost. In early spring, plant the crowns at or just below the soil surface in their garden site and water until they are well established. You generally don't need to pinch the plants, but you may need to stake tall plants such as stocks and mallows. Most biennials have a short flowering season, more like perennials than annuals.