Ruby Spice summersweet

Sun

Full sun to partial shade; tolerates deeper shade but flowers less freely. Afternoon shade is helpful in hot climates.

Water

Keep the root zone consistently moist, especially during establishment and hot weather. Tolerates periodically wet ground but performs poorly in prolonged drought.

Soil

Moist, humus-rich, acidic soil is best. Tolerates clay and occasional waterlogging; avoid dry, chalky or strongly alkaline soil.

Height

4-6 ft (1.2-1.8 m)

Spread

3-5 ft (0.9-1.5 m), eventually wider if suckers are left to grow

Flowers

Mid- to late summer; fragrant, deep pink flowers in upright spikes, retaining their pink colour as they age.

Foliage

Oval, toothed green leaves turn yellow to golden brown in autumn. Leaves emerge relatively late in spring.

Growth

Slow to moderate

Care needed

Low

• Pollinators
• Deer resistant
• Cold hardy
• Heat tolerant
• Wildlife
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   2.1 ft (0.65 m)

3. After 2 years

   2.7 ft (0.81 m)

4. After 3 years

   3 ft (0.96 m)

5. After 5 years

   4 ft (1.3 m)

About 7 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US and Canada

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Slow

• Water deeply during dry spells; do not let newly planted shrubs dry out.
• Apply 2-3 in (5-8 cm) of leaf mould or composted bark over the root zone, keeping it clear of the stems.
• In spring, top-dress with compost; use an acid-loving plant fertiliser only if growth is weak.
• Remove unwanted suckers at their point of origin to keep the clump within bounds.
• Leave room for its mature width rather than repeatedly clipping it into a tight shape.

Pruning. Prune in late winter or early spring, removing dead, damaged or crossing stems and, if needed, a few of the oldest stems at ground level. Flowers form on the current season's growth, so avoid pruning new shoots later in spring or summer.

Late winter

Thin crowded growth and remove dead or damaged stems before new growth begins.

Spring

Plant when the ground is workable, water thoroughly and mulch the root zone.

Late spring

Check moisture as growth starts; allow for naturally late leaf emergence before assuming stems are dead.

Summer

Water during dry periods, particularly while flower spikes are developing.

Late summer

Enjoy the flowers; deadheading is optional and is not needed for plant health.

Autumn

Remove unwanted suckers and replenish mulch after the soil has been moistened by rain.

• Plant beside a path or seating area where the summer fragrance can be appreciated.
• Group along a moist woodland edge with ferns and shade-tolerant perennials.
• Use as an informal flowering hedge, allowing enough width for its spreading habit.
• Include in a rain garden on ground that stays moist but is not permanently submerged.
• Combine with white-flowered shrubs and dark green foliage to make the pink flower spikes stand out.

Garden styles it suits: Woodland, Wildlife garden, Pollinator garden, Sensory garden, Cottage garden and Bog garden.

Plant it with: Virginia sweetspire, Oakleaf hydrangea, Cinnamon fern, Royal fern, Astilbe and Sedges.

Wildlife: The fragrant flowers attract bees, butterflies and other nectar-feeding insects. Dense growth offers cover for small wildlife, and birds may take some of the seeds.

• Drought stress causes wilting, scorched leaf edges and poor flowering: water deeply and maintain an organic mulch.
• Yellow leaves with greener veins can indicate alkaline soil: check soil pH and relocate to acidic soil if necessary rather than repeatedly feeding.
• Spider mites may cause fine stippling and webbing during hot, dry weather: improve watering and rinse leaf undersides with water.
• Sparse flowering often follows deep shade or late pruning: provide more light and restrict pruning to late winter or early spring.

Not known to be toxic to cats, dogs, horses or people. No part is recognised as a serious poisoning hazard, but it is an ornamental plant rather than a food plant.

• Virginia sweetspire (Itea virginica)

  Usually flowers earlier, with arching or drooping white flower spikes rather than upright pink spikes; its autumn foliage is often red or purple.

• Japanese clethra (Clethra barbinervis)

  Becomes a much larger shrub or small tree with conspicuously peeling, mottled bark and branching clusters of white flowers rather than pink spikes.

Clethra comes from the Greek name for alder, and alnifolia means alder-leaved, both referring to the resemblance of its foliage to alder leaves.

Propagation. Take softwood cuttings in late spring or early summer, or detach well-rooted suckers during dormancy. Vegetative propagation preserves 'Ruby Spice'; seedlings will not reliably match the cultivar.

Accepted botanical name

Clethra alnifolia

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Alabama, Connecticut, Delaware, Florida, Georgia, Louisiana, Maine, Maryland, Masachusettes, Mississippi, New Hampshire and New Jersey.

Measured

Soil pH 4.5 to 7. Average height 394 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.