The Summersweet (Clethra Alnifolia) Care Guide

The Summersweet, otherwise known as the Clethra Alnifolia or Coastal Pepperbush, Coastal Sweet Pepperbush, Coastal Sweet Pepper, Alderleaf Pepperbush, Alderleaf Clethra, Clethra, Summer Sweet, Clethra tomentosa, is a somewhat well known shrub plant native to the Southeast, Northeast, and the Southwest of the United States.

Best known for its low maintenance and moderate growth, this shrub will likely liven up your house (or garden) with its dark green colored leaves. But, only if you learn how to take proper care of it for it to thrive.

This is why all the topics you need to know in order to achieve this will be covered in this Summersweet Care Guide. Ready? Let’s go!

The fundamental caring guidelines for every Summersweet can be summed up into the following:

  • Water: The Summersweet loves moist soil but will still survive dusty soil when it is established.
  • Light: Keep your Clethra Alnifolia in an environment where it can receive partial shade to full sun on a daily basis. 
  • Soil: Make sure to keep the Summersweet in soil with moist but well-draining properties, so ideally, one that is made of sand, loam, and clay.

And as with many other plants, these are the only three care factors you need to remember to make sure your Summersweet is, for the most part, healthy and well to survive.

Clethra Alnifolia flowers

Scientific / Botanical Aspects

In botanical terms, the Summersweet belongs to the Clethraceae family, the genus Clethra and the species Alnifolia, hence its scientific (or botanical) name Clethra Alnifolia (KLEE-thra al-nee-FOH-lee-uh).

As with other Clethra’s, the Summersweet is a deciduous plant, which means it will shed its leaves annually once autumn comes.

Growing Region

The Summersweet is a plant native to the Eastern USA. This is why the Clethra Alnifolia is used to growing in specific regions such as the states in Southeast, Northeast, and the Southwest of the United States.

You might be wondering why your Summersweet’s native region is important. Well, if you know where your plant originally came from, you’ll know which environment conditions it prefers, and with it, knowledge on how to replicate it at home.

With this in mind, the Clethra Alnifolia will be most used to the heat zones in the 1 – 9 region, as the plant hardiness level falls between 3a, 3b, 4a, 4b, 5b, 5a, 6a, 6b, 7a, 7b, 8a, 8b, 9b, 9a and the ideal climate zone is between 1, 1A, 1B, 2, 2A, 2B, 3, 3A, 3B, 4, 5, 6, A2, A3.

Growth and Size


In terms of size and growth, the Summersweet is a relatively moderate grower, which makes things somewhat easy for any plant enthusiast.


But, how big does the Summersweet actually get? What should you expect in terms of size? Let’s dive right in…

The Clethra Alnifolia can grow up to 3′ – 8′ (90cm – 240cm) in 3′ – 8′ (90cm – 240cm) and 4′ – 6′ (120cm – 180cm) in 4′ – 6′ (120cm – 180cm). 

These dimensions make the Summersweet a relatively large shrub compared to others, so it’s best to keep this fact in mind since it will affect where you want to keep yours at home.

Also, expect it to grow in a wonderful rounded shape, which is something worthwhile to remember when making your garden landscape plans.

This is why experts recommend keeping an area of approximately 48″ – 72″ (120cm – 180cm) free so the Summersweet can spread to its best extent.


In terms of watering, the Summersweet is a fairly complicated plant to take care of.

This is mostly because it has a not so straightforward watering schedule and somewhat regular watering needs.

Specifically, most experts agree that the Clethra Alnifolia loves moist soil but will still survive dusty soil when it is established.

Which is why it is considered a plant with relatively average needs in terms of water. 

Clethra Alnifolia care


As a rule of thumb, you should remember to keep your Summersweet in soil with moist but well-draining characteristics, as these will guarantee the right conditions for your plant to grow and thrive. 

When you consider this, this is why you should aim to choose soil that has good drainage, moist, and occasionally wet properties to keep the right moisture levels at all times. 

However, in our experience, the best solution to knowing the right amount of water for your Summersweet is with the ‘thumb’ technique. Basically, you insert your finger into the soil, and based if you feel the soil moist or dry, you determine if it needs any water, which is the most appropriate way to go about watering your leafy friend.

Soil Mix

As mentioned earlier, the Summersweet prefers to have soil with good drainage, moist, and occasionally wet properties at all times, reason why you need to make the soil mix out of sand, loam, and clay.

This is why most experts agree that the Summersweet requires soil with clay, high organic matter, loam (silt), and sand, which will give you the right conditions it needs.

In addition to this, expert gardeners recommend having preferably acid soil.

Light and Exposure

In terms of light & exposure, the Summersweet requires partial shade to full sun in order for it to thrive under the right conditions. 

Most experts agree that this shrub will do well as long as you keep it in shade, or partial sun to full sun, and it will be able to grow properly.

Specifically, we recommend that you place your Clethra Alnifolia in from full or deep shade (no direct sunlight or at most 2 hours per day), to little to partial shade (only 2-6 hours of direct sunlight a day), to full and direct sun (more than 6 hours of direct sunlight per day).


Being a deciduous plant, the Summersweet will shed its leaves annually once autumn comes.

But, you can expect it to have its ‘prime-time’ during the summer (mid, late), and during the fall.


You can expect your Summersweet to flower around the summer months from July to September (summer).

In particular, this shrub is well known for its fragrant and showy flowers around the plant enthusiast community.

The Summersweet produces some beautiful white, or pink and white flowers around this time of year.


The leaves from the Summersweet have a beautiful dark green color during most of the year.

In particular, they have a simple arrangement with a alternate organization in its leaves.

You can expect the leaves from your Clethra Alnifolia to be around (3-6 inches) in size.

Clethra Alnifolia and bees

Attracts, Tolerance and Resistance

The Summersweet is well known for being able to attract butterflies, birds and hummingbirds, so keep that in mind when choosing your plant, as you’ll likely end up finding one or another in your garden.

Additionally, it has a special tolerance for salt, clay soil, wet soil, and animals like deer, so don’t worry if any of these come along, your Clethra Alnifolia will be fine.


Does your Summersweet have any garden recommendations? Does it serve any gardening purposes? Here’s how you can get the most out of your new plant.

Most Clethra Alnifolia owners agree that this shrub will look great in most cottage gardens of all types. 

Other owners consider that they complement well most gardens of prairie and meadow, coastal garden, informal and cottage, and in traditional garden styles. 

In particular, the Summersweet’s best location within your garden is in beds and borders, and in ponds and streams, others use it for landscaping in a very wet areas, mass planting, hedge, firescaping/fire wise, container, coastal exposure, border, or a woodland garden.

Companion Plants

Summersweet’s do well with some other plants beside it. One good companion plant is the Buxus, which will pair up nicely with your leafy friend.

Others consider that a nice Weigela will work well too, so choose whichever you find works best for you!


So that’s it! These are the main plant care requirements that you need to keep in mind in order to have a healthy Summersweet in your garden or home.

Martin Duran

Hey y'all! My name is Martin Duran and I am from Cali, Colombia. Since 2018 I have been learning about plants and how to take care of them. Here's is my journey... “The clearest way into the Universe is through a forest wilderness.” ― John Muir

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