Hummingbird summersweet

Sun

Full sun to partial shade; give afternoon shade in hot climates. It tolerates deeper shade but flowers less freely.

Water

Keep the root zone consistently moist, especially during establishment and hot weather. Established plants tolerate wet ground better than prolonged drought.

Soil

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

Height

2-4 ft (0.6-1.2 m)

Spread

3-5 ft (0.9-1.5 m), eventually wider if suckers are retained

Flowers

Fragrant white flower spikes from midsummer into early autumn, depending on climate.

Foliage

Oval, toothed, dark green leaves that usually turn yellow 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

   1.8 ft (0.56 m)

3. After 2 years

   2 ft (0.62 m)

4. After 3 years

   2.2 ft (0.68 m)

5. After 5 years

   2.7 ft (0.81 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 so the soil stays moist rather than drying out completely.
• Apply a 2-3 in (5-8 cm) layer of leaf mould or composted bark in spring, keeping it clear of the stems.
• Feed lightly in spring only if growth is weak; use a fertiliser suitable for acid-loving shrubs.
• Remove unwanted suckers near their point of origin to keep the clump within its space.
• In hot, dry areas, choose a sheltered position with afternoon shade and reliable irrigation.

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

Early spring

Plant when the soil is workable and moist, and water thoroughly.

Early spring

Remove dead wood, thin congested old stems if necessary, and cut out unwanted suckers.

Spring

Renew the organic mulch; feed lightly only where growth or soil fertility is poor.

Summer

Check soil moisture regularly and water deeply during dry weather.

Early summer

Take softwood cuttings from healthy, non-flowering shoots.

Autumn

Plant or move shrubs while the soil is moist; in very cold regions, leave planting until spring.

• Plant beside a path or seating area where the summer fragrance can be enjoyed.
• Group beneath lightly shading deciduous trees with ferns and moisture-loving perennials.
• Use as a low, informal hedge or repeated shrub along a damp border.
• Plant on the moist margins of a rain garden, allowing room for the colony to widen.
• Combine with pink astilbes and dark green foliage for a shaded summer border.

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

Plant it with: Astilbe, Cinnamon fern, Japanese painted fern, Hosta, Virginia sweetspire and Rhododendron.

Wildlife: The fragrant flowers supply nectar and pollen to bees, butterflies and other insects. The suckering clump provides low cover, and persistent seed capsules can add winter structure.

• Yellow leaves with green veins can indicate alkaline soil: test the soil and, where it is strongly alkaline, choose another site or grow in a large container of ericaceous compost.
• Wilting, scorched leaf edges or poor flowering can follow drought: water deeply and mulch to keep the root zone cool and moist.
• Spider mites may cause fine stippling and webbing during hot, dry weather: rinse leaf undersides and correct moisture stress.
• Sparse flowering can result from deep shade or pruning after shoots have developed: provide brighter light and prune only in late winter or early spring.

Not known to be toxic to cats, dogs, horses or people. No part is generally identified as poisonous, but it is an ornamental shrub rather than a food plant.

• Virginia sweetspire (Itea virginica)

  Its white flower spikes usually arch or droop and appear earlier, in late spring to early summer. Its autumn foliage is often red or purple rather than the mainly yellow colour of summersweet.

• Mountain pepperbush (Clethra acuminata)

  A much taller shrub or small tree with larger, long-pointed leaves, arching flower spikes and conspicuously peeling cinnamon-coloured bark.

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 early summer, or detach well-rooted suckers during dormancy. Use vegetative propagation to retain the 'Hummingbird' cultivar; seedlings will not reliably match it.

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.