Spirea

About Spirea

Spireas are some of the easiest flowering shrubs: fast-growing and generally deer resistant, with spring kinds covered in tiny white flowers and summer kinds with flat pink clusters that draw butterflies (Clemson). Japanese spirea (S. japonica) and its bumalda hybrids escape into woods and are listed as invasive in Virginia, Georgia, South Carolina, Tennessee, Kentucky and North Carolina, so Southeastern extension services don't recommend them. NC State suggests native alternatives such as New Jersey tea, dwarf fothergilla, Virginia sweetspire, mountain laurel and ninebark.

Most spireas grow in zones 3-8 (Clemson, NC State). Japanese spirea is invasive in the Southeast and in the Great Smoky Mountains (NC State, Clemson).

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Fall is the best planting time, and late fall after the leaves drop is best for moving plants (Clemson). Mulch, and water in summer with drip rather than sprinklers.

Soil

Almost any well-drained soil; avoid soggy spots, where Phytophthora and Pythium root rots strike (Clemson).

Test the soil before planting; mature shrubs in decent soil need little or no fertilizer (Clemson).

Feeding

• Spring to early summer after new growth starts, only if a soil test shows a need: slow-release complete fertilizer in a 3:1:2 ratio, or what the soil test calls for. Spread evenly from the trunk out to the drip line and water it in; a typical soil-test rate for shrubs is about 2 lb of 12-6-6 per 100 sq ft (Clemson). Follow a soil test.

Water is what new shrubs need most: daily for the first 2 weeks, every 2-3 days through week 12, then weekly until the roots spread (at least two growing seasons), using about a quarter to a third of the nursery pot's volume each time (UMN). Mulch and water in summer, using drip rather than overhead sprinklers (Clemson).

Harvest

Spring bloomers (bridalwreath, Vanhoutte, Thunberg) flower white in early to mid spring: prune them right after bloom and take a few old canes to the ground each year. Summer bloomers (Japanese and bumalda types) flower pink in June-July on new wood: prune in late winter or early spring, and shear off spent flowers for a second flush (Clemson).

Varieties (13)

Clemson and NC State document these. Japanese and bumalda spireas are invasive in the Southeast and not recommended; the last group is listed so gardeners can recognize them.

Pests to watch for

Aphids, Scale insects

Diseases and problems

Phytophthora root rot, Leaf spot, Powdery mildew, Fire blight

In the kitchen

Safety: No toxicity is listed for spirea in the extension sources we used.

Pets: Not on the ASPCA toxic plant lists.