Planting a Staggered Border With Thuja Plicata

Space to Grow

• Western red cedar is not a small tree, growing to at least 50 feet tall and 15 to 20 feet wide. When planning a staggered border, it is critical to include enough room for the mature spread of the cedars. This is made easier by the fact that from its inception, the planting scheme will contain other species between the cedars. As years pass, some of the smaller plants in between the cedars can be moved to accommodate their increasing space requirements.

Moist, Shady Conditions

• Native to the cool, moist climate of the Pacific Northwest, Western red cedar thrives in uniformly moist, well-drained soil in full sun. This means, however, that border plants will be shaded by the cedars. Generally speaking, for a border, choose a mix of evergreen and deciduous plants that share the same need for moisture. All should tolerate partial shade, and those planted closest to the base of the cedars must be tolerant of nearly full shade.

Understory Shrubs

• If the border area is large, consider using shrubs as understory plants. One good choice is oakleaf hydrangea (Hydrangea quercifolia), hardy in USDA zones 5 through 9. The plants stand 3 to 6 feet tall and bear large, pyramidal clusters of white flowers in late spring or early summer. Oakleaf hydrangea thrives in uniformly moist soil and partial shade. Another good flowering understory plant is Japanese kerria (Kerria japonica), with golden single flowerings and a preference for moist soil and partial shade. Hardy in USDA zones 5 through 9, the plants also grow 3 to 6 feet tall

Smaller Plants

• Many perennials and some annuals will provide color and interest alongside Western red cedar in a staggered border. Japanese painted fern (Athyrium niponicum var. pictum), hardy in USDA zones 3 through 8, grows 12 to 18 inches tall, with fronds marked in gray-green and silver. Lenten rose (Helleborus orientalis) is evergreen, with wide, palmate leaves and early spring flowers in a wide variety of shades. The flowers last on the plants up to six weeks. Lenten rose grows 12 to 18 inches tall and is hardy in USDA zones 4 through 9.