How to Grow the Summersweet Shrub: Plant Care Guide

Published June 9, 2022
Clethra alnifolia summersweet flowers

If you're looking to enhance your garden with a gorgeous flowering shrub that will grow in all light conditions, summersweet (Clethra alnifolia) is a great plant to consider. This deciduous shrub, which is sometimes called sweet pepperbush, grows to reach between three and eight feet tall and spreads to between four and six feet wide. It blooms in mid to late summer (usually July and August), producing long clusters of fragrant white or pink bottlebrush-style flowers.

Summersweet Flower Characteristics

Growing Summersweet Shrub in Your Garden

Does summersweet sound like a must-have plant for your garden? Learn what you need to know to grow this showy shrub in your yard.

When to Plant Summersweet

Wondering when to plant summersweet? This deer-resistant shrub can be planted in early fall, well in advance of the first freeze of the year, or in early spring. You don't have to wait until after the last frost; you can plant once the ground has thawed.

Where to Plant Summersweet: Light and Soil Requirements

Summersweet will thrive in just about any light conditions, though it does prefer soil that is at least somewhat acidic. Summersweet is generally hardy in USDA Zones 3-9.

  • Summersweet will grow and bloom in full sun, part shade, or full shade.
  • This shrub grows best in soils with a pH between 5.0 and 6.9, which is acidic.
  • It will also grow in soil that has a pH between 7.0 and 7.5, which is neutral.
  • As long as the soil has an appropriate pH, summersweet will grow in clay, sand, or loam.
  • It will tolerate poor soil but does best in well-draining soil that is rich in organic matter.

Watering and Fertilizing Summersweet

If you properly plant and water a young summersweet plant, you will help set it up to thrive with very little maintenance required.

  • Plant this shrub in a hole that is around four times as deep and wide as the plant's root ball.
  • When you first plant summersweet, place it in the hole you dug and fill the hole with water.
  • Wait for the water to drain, then fill the hole with the soil you dug out to make it.
  • Once the hole is filled in, water the newly planted shrub again.
  • Place your favorite type of mulch around the plant's base.
  • Summersweet likes moist soil that drains well. You'll need to water it when the soil becomes dry.
  • It does not tolerate drought conditions; when conditions are dry for an extended period, you'll need to water regularly.
  • Fertilize summersweet during the spring. Use an organic plant food or a slow-release shrub and tree fertilizer.
  • Do not fertilize immediately after planting; wait for the plant's roots to have time to get established first.
  • If needed, add more fertilizer or feed with organic plant food once during early summer.

Pruning Summersweet

It is best to prune summersweet in late winter or early spring, shortly after new leaves begin to grow. Depending on plant size, use loppers (for larger shrubs) or bypass pruners (for smaller shrubs). This can help control the size of the shrub as well as get it to grow into a shape that works well in your landscape. Summersweet blooms on new growth, so it's best to prune out older branches. Be sure to remove any that are dead or have damage.

Close-up image of Summer Sweet bush in blossom

Summersweet Shrub Pests and Diseases

Summersweet is not plagued by much in the way of pests and diseases, but there are a few minor concerns.

  • Spider mites can target summersweet when conditions are very dry. Treat leaves with a substance like a neem oil or peppermint oil spray to get rid of spider mites.
  • If it is very rainy late in the season, the leaves can develop Pseudocercospora leaf spot disease. Since the leaves drop in the fall, treatment is generally not required.

Propagating Summersweet

It's not difficult to propagate summersweet. You can grow it by planting seeds in the fall, as they'll need to overwinter outdoors before sprouting. You can also grow it by rooting softwood stem cuttings.

  • The best time to take softwood cuttings for propagation purposes is early summer.
  • Ensure the plant is in moist soil before taking cuttings. If conditions are dry, water the plant first.
  • Snip three to four inches long stem cuttings from the mature plant. It's best to take cuttings in the morning.
  • For best results, dip cuttings in a rooting hormone that contains Indole-3-Butyric Acid (IBA), then plant them in soil. It takes around a month for roots to develop.
  • The later in summer you take cuttings, the more important it is to use rooting hormone. Early summer cuttings may root well without it.
  • Once rooted, you can plant your propagated plant in your yard in the fall or put it in a container to let it grow before planting it in the spring.

Beautiful Summersweet to Grow in Your Garden

There are several summersweet cultivars to consider. Choose plants that offer the size and flower color most appropriate for your planting location and landscape.

Hummingbird Summersweet

If you're looking for a compact summersweet plant, you can't go wrong with the hummingbird cultivar. This cultivar grows to between three and four feet tall, so it's ideal if you want to keep plants this size without having to do a lot of pruning. Hummingbird summersweet has white flowers.

Ruby Spice

If you want a compact summersweet cultivar but you'd prefer to add pink blooms to your landscape, consider the ruby spice cultivar. It doesn't generally grow beyond four feet tall and produces striking bright pink flowers that really stand out in a summer landscape.

Vanilla Spice

For a somewhat larger summersweet plant with white blooms, consider incorporating vanilla spice summersweet into your landscape. This type reaches between three and six feet in height. Its floral blooms are a bit larger than some other kinds of summersweet.

Rosea

If you're looking for a full-size summersweet plant that offers blooms in two shades, the rosea cultivar is a good option. When this tall summersweet first blooms, its flowers are a lovely shade of light pink. However, over time, this unique cultivar's delicate pink flowers fade to become white.

Good Companions for Summersweet

Summersweet can be paired with other plants that like moist soil. They work well as understories for many types of trees since they can tolerate part or full shade, though they don't have to be planted under trees since they also tolerate full sun. When looking for flowers to plant in front of or beside summersweet, opt for annuals or perennials that will grow in part shade. You can also pair summersweet with other shrubs. Good options include.

Enhance Your Yard With Summersweet

If your landscape will benefit from the addition of a bushy shrub, you can't go wrong with summersweet. Not only is summersweet beautiful, but its blooms will attract bees, hummingbirds, butterflies, and beneficial predatory wasps to the area where it is planted. The leaves will turn a lovely yellowy color during the fall, so summersweet even adds a bit of color to your landscape after the blooms have stopped. Find a spot that needs a shrub and plant some summersweet today!

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How to Grow the Summersweet Shrub: Plant Care Guide