Artemisia 'Powis Castle'

Evergreen, quick-growing perennial that forms wonderful silver-grey clumps. Spreads via underground rhizomes, which may reach 2m wide if not restrained.

This woody perennial has finely-divided, fragrant silver foliage. Occasional insignificant dull yellow flower heads are produced in late summer.

Best grown in poor to moderately fertile, dry soils in full sun. Excellent soil drainage is essential for growing this plant well. It performs poorly in moist to wet soils, where plants are susceptible to root rot.

With suitable preparation and care, perennials will grow and flower well year after year. They benefit from a weed-free well-drained soil rich in organic material.

Prepare the planting site when soil is moist and easily worked, such as after the first rains in spring and autumn. Remove all weeds and incorporate bark, compost or other organic material. Before planting, ensure the root ball is saturated and remove the planter pot with minimal root disturbance. Trim any broken roots and plant at the same level as in the container. Dig a hole twice the diameter of the root ball, press in and water once planted. Planting too closely leads to spindly growth, poor flowering and eventual plant decline. In a well-planned border, the plants in flower should just touch each other to create a full effect without overcrowding.

Make sure plants are watered well until established if planting in a drier period. Plant with a general slow-release fertiliser. After this, apply organic fertiliser, such as blood and bone, at a handful per square metre, in spring. Avoid heavy, wet soils and overcrowded plantings. Good air movement keeps foliage dry; avoid overhead irrigation. Before planting, improve drainage by incorporating coarse gravel, such as GAP 40, into the planting hole. Artemisias hate wet conditions.

Stake plants at or near planting time to ensure the plants are not damaged and grow around the stakes.

Apply mulch annually to help suppress weeds and conserve moisture. Woody perennials need regular pruning to keep tidy. Prune plants in spring to control growth, but be careful to leave sufficient numbers of live buds on each stem to facilitate bushy growth. Never prune stems to the ground. Foliage may also be lightly sheared in summer to shape, but avoid pruning in autumn. Unless the soil is very poor, no fertiliser is required. An annual application of lime to acidic soils is beneficial, as many of these silver plants are found naturally growing on limestone formations.

Can get aphids and gall midges. Susceptible to root rot in moist, poorly drained soils.

Perennial Garden

The silver-grey appearance of this species is due to a layer of white hairs on the leaf surface. This is an adaptation to reduce water loss, keep leaves cool and to protect the plant from the cold at night. Plants with grey foliage are usually more tolerant of drier conditions than other plants.