Spiraea is a flowering deciduous bush that is easy to grow and maintain. Among the 80 species of spiraea are just two basic flowering habits. The bridal wreath spiraea has cascading white spring blooms and is more erect than low-growing spiraea. The low, shrubby form tends to have rangy branches and produce clouds of pink, red or white flowers from spring until fall. These plants are useful in full to partial sun locations and can tolerate short periods of drought once established. All species of spiraea bushes may be cut back completely after flowering and will renew themselves the following spring.
Use a pair of pruners to cut a terminal stem containing leaves and a flower if they are in bloom. Stems of a spiraea bush are woody once they reach a diameter of 1/8 inch and snap off easily. The very tip will still be green and bendable. In the interior of a spiraea bush the wood is 1/2 inch to 1 inch thick and is very hard to cut with hand pruners.
Measure the length of a leaf. Spiraea have leaves between 1 and 3 inches long depending upon the species. The leaves are greyish green and have slight serration on the edges. They are slim, lance-shaped leaves with a terminal point. New leaves will often have a pinkish tinge to them. All the foliage deepens to a rose colour when temperatures cool in fall.
Examine the flowers of the spiraea. They consist of many tiny flowers clustered into corymbs or clusters that may be drooping or bunched. The tiny flowers have a feathery or fine, hairy texture to them and are produced in rose, white, pink and red hues. Flowers are present on spiraea bushes in spring and summer. They turn brown as they age.
Check the size of the plant at the end of the growing season. Spiraea bushes grow rapidly, adding 12 to 18 inches in height annually until they reach their maximum height, which may range from 2 to 10 feet. Their spread may reach 20 feet. The majority of the commonly grown species are only 2 to 6 feet tall with a similar width.
Note the growth form. Spiraea have arching or upright woody stems. The branches may become long on the vertical growth type spiraea bushes, but their width does not equal their height. Spreading types have a low mounding habit, and they often stretch out many times wider than their height. Branches remain thin, with even the oldest rarely attaining more than 3 inches in diameter. Spiraea have nice, thick canopies and dense growth.