A steeplebush, botanical name either Spirea douglasii or Spirea tomentosa is a large shrub which is tolerant of a wide range of conditions. This deciduous plant is very easy to grow and maintain, and a number of cultivars have been developed. Native to much of the U.S. and Canada, the steeplebush has been naturalized across the world. It is a popular garden plant, particularly for those who wish to attract and encourage wildlife.
Reaching heights of 6 feet (1.8 meters), the steeplebush spreads outward, forming dense clumps if grown in optimal conditions. This plant prefers full sun and moist soil, but can grow in almost any conditions. It tolerates all soil types and a wide pH range of 6.1 to 7.8. The only consideration is that it must have moist soil to remain healthy; this is particularly important for younger plants. Once mature, this species can tolerate periods of drought, but flower production will decrease or stop during very dry conditions. If the plant is exposed to prolonged periods of drought, the growth rate will slow and it will suffer poor general health, thereby leaving the plant open to disease and insect damage.
This hardy shrub can be grown in exposed locations because it does not suffer damage from wind and weather exposure. A variety of different cultivars have been developed that are tolerant of an even wider range of conditions and provide additional disease and pest resistance. These cultivars also provide a gardener with a wider range of color choice, ranging from pastel pink to purple. The steeplebush produces long, erect stems full of tiny, tightly clustered flowers. After flowering, small fruits appear which turn brown as they mature.
This plant is easy to grow from seed even for a novice gardener. To control growth and spread, the steeplebush can be heavily pruned or cut back after the last flowers have died off. With this species rapid growth rate, it will quickly recover; by the following spring it will produce masses of healthy new stems and foliage.
The dense clumps at the base of the plant provide shelter and a damp, shady environment for small animals such as frogs, lizards, mice, and voles. The flowers also attract a wide range of butterfly species as well as other insects. This makes the steeplebush useful as a companion plant in the vegetable garden, because it attracts bees, which will pollinate other plants. While normally attacking vulnerable vegetable plants such as cabbages, kale and broccoli, butterflies tend to lay their eggs on and feed on the steeplebush instead.