Summersweet
Clethra alnifolia
also called sweet pepperbush, clethra
Spiced-honey perfume in the last weeks of July from upright white bottlebrush spikes, on a tidy native shrub that blooms in shade, stands in wet ground and hums with every bee in the neighborhood.
- Type
- Shrub · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Flower color
- White
- Sunlight
- Part shade to sun; it blooms well even in real shade
- Watering
- Moderate to high; the wet corner is fine
- Soil
- Moist to wet, acid; one of the few fragrant shrubs for shade
- Feeding
- Gentle all-organic
- USDA zones
- 3b–9a
- Frost tolerant
- Yes
- Plant out
- at the last spring frost
- Plant spacing
- 4 ft 11 in
- In-row spacing
- 3 ft 11 in
- Between rows
- 6 ft 7 in
- Square-foot density
- Not suited to SFG
- Root system
- Woody and fibrous
- Working depth
- 12–24 in
- Can reach
- 3 ft down where the soil allows
- Spread
- 10–13 ft across, about 1.5–2× the width of the plant
- Shallowest pot
- 20 in of soil
A shallow woody framework with the fine feeding roots in the leaf litter above it. Those feeders are mostly under the outer half of the canopy rather than against the stem, which is where water and feed should go.
It suckers into a colony, particularly in the damp ground it prefers, so give it room to widen or plan on lifting the strays each spring.
The habit is Summersweet’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- When
- Not harvested. Prune, if wanted, in early spring, since it blooms on new wood.
- What to look for
- Suckers widening the clump past its welcome; old stems getting twiggy.
- How to harvest
- Cut a few of the oldest stems to the base in March and pull wandering suckers while the ground is soft. That is the entire program.
- How often
- Every year or two.
- Storing the crop
- Nothing to store. Leave the seed spikes standing: they hold the bottlebrush shape all winter and feed the finches.
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Big-eyed bug Geocoris spp.Hunts Spider mites
A stubby 3 mm bug with enormous wrap-around eyes, working the soil surface and the low foliage for aphids, mites, thrips and insect eggs. It is the main natural check on chinch bugs in a lawn and it is killed outright by insecticide.
- Green lacewing Chrysoperla carneaHunts Spider mites
Its bristly larvae — "aphid lions" — impale aphids, mealybugs, thrips, and mite colonies, eating hundreds a week. Adults feed on nectar and pollen from small open flowers and overwinter in hollow stems left standing.
- Ladybird (lady beetle) CoccinellidaeHunts Spider mites
The gardener’s favorite ally: adults and their alligator-shaped larvae each eat thousands of aphids, plus scale, mealybugs, and other soft-bodied sap-suckers. Grow flat, open flowers for the adults and never spray a colony that ladybird larvae are already working.
- Minute pirate bug Orius spp.Hunts Spider mites
A pinhead-sized true bug that is the best natural check on thrips, and happily spears aphids, mites, and insect eggs too. It needs pollen when prey is scarce, so keep something flowering nearby.
- Predatory mites Phytoseiulus & AmblyseiusHunts Spider mites
Fast orange mites that hunt spider mites egg-by-egg, and cousins that clear thrips and fungus-gnat larvae. Sold as a biological control for greenhouses; outdoors they follow humidity — mist and mulch, don’t dust with sulfur.
- Rove beetle StaphylinidaeHunts Spider mites
Slim, quick beetles with short wing cases that hunt in soil and litter, taking root-fly eggs and larvae, fungus-gnat larvae, and mites. Mulch and undisturbed ground keep them resident year-round.
It flowers on new wood in high summer when almost no other shrub does, which makes it the bridge between the spring shrubs and the asters. It leafs out very late in spring; every year somebody digs one up believing it dead.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com