On Gardening/Spirea Is For All Seasons

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University Park, Pa. -- Just about any garden or nursery catalog you look at these days will contain numerous "new" and "improved" plants for the landscape. Such plants generally do exhibit a new or unique quality when compared to similar species or selections. However, there are a number of older and time-tried plants that still have a place in the modern landscape.

Such a selection would be one of the various species of Spiraea, pronounced spy-ree-ah, which provide a range of flowering times, colors and sizes for just about any landscape situation. Flower colors are pure white to bright pink, to crimson-rose and some in between. Flowers appear from early spring to early summer depending on the type selected.

Spirea,, the plant's common name, come in many sizes ranging from 2 to 8 feet tall. With that wide a selection, spirea can be used as an ornamental accent, to form a hedge, in a rock garden, or as a low border along a walk or drive.

Spirea is also easy to care for in the garden. It require little if any seasonal pruning. In fact, it responds well to periodic rejuvenation pruning where it is cut back severly and allowed to grow back. Seasonal thinning of longer stems will retain a fuller and denser plant. Spring blooming species are cut back after flowering, and varieties that bloom later in the summer are pruned in early spring. The plants have no serious pests other than a few aphids in the spring, and most species are very hardy in all areas of Pennsylvania.

Some of the larger species include Spiraea prunifolia - Bridalweath spirea and S. vanhouttei - Vanhoutte spirea, which have white spring flowers on plants that may reach 6 to 8 feet tall. These make ideal backgrounds and border selections. A similar sized plant with rose-pink flowers that open from spring to summer is S. x billiardii - Billard spirea.

A good selection growing only 3 to 5 feet tall with white spring flowers is S. thunbergii - Thunberg spirea. This plant has very slender leaves on thin twigs that create a gentle arching habit. It does well in front of taller plants in a border.

Where smaller or lower plants are required, consider planting S. x bumalda 'Anthony Waterer' - Anthony Waterer spirea, which usually grows about 2 to 3 feet tall. The plant has an upright habit of growth, and produces a carmine-pink cluster of flowers at the ends of the stems in June. Sparsely scattered among the dark green leaves are a few white variegated leaves that add seasonal interest in the summer.

A number of selected cultivars from S. japonica - Japanese spirea grow about 2 feet tall. The cultivar 'Little Princess' produces a mound with pink blossoms in June, while 'Shirobana' may grow slightly taller but produces deep rose, pink and white flowers on the same plant in late spring and early summer.

All spirea are well-adapted to any moist, well-drained that is slightly acidic.

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Dr. Nuss is a horticulturist at Penn State. He coordinates all extension horticulture programs. He has bachelor's, master's, and doctoral degrees in ornamental horticulture and has been on the Penn State faculty since 1966.