How to Plant, Grow, and Care For Japanese Stewartia

Imagine a beautiful white camellia that blooms in the summer. That is Japanese stewartia, a close relative of this favorite blooming evergreen, with a twist. Trees that offer interest during all four seasons are rare, and when we happen upon one, you’d better believe we want to know everything about it. 

Here is all you need to know about growing the stunning Japanese stewartia!

What Is Japanese Stewartia?

Japanese stewartia is a wonderful, large shrub or small tree that can grow into a quite imposing figure. It is similar to a camellia, and the flowers are nearly identical to some single-flowered varieties. It creates a striking figure in the landscape, with plenty to look at during all four seasons, quite a rarity.

Characteristics

Japanese stewartia is a deciduous tree that ranges from 12 to 40 feet tall, with a slightly smaller spread. It’s multi-stemmed and shrubby in habit, growing in a pyramidal to oval shape. The branches start low to the ground, and the ovate leaves have serrated margins, are medium green, and heavily textured. 

These plants leaf out in early spring before blooming between June and August. The flowers strongly resemble a single-petaled camellia bloom, with five creamy white petals and a crown of golden stamens in the center. They are small to medium-sized, at two to three inches in diameter. 

This tree diverges from its relatives in fall, when, rather than retaining evergreen foliage, the leaves change to vivid shades of red and orange. They add brilliance to the fall landscape before going dormant for the winter. 

In winter, with the foliage absent, the beautiful peeling bark reveals itself, adding interest to the cold, dreary months. The bark resembles that of a crape myrtle, with older grey strips peeling away to reveal shades of white and cinnamon underneath. 

Native Area

This slow-growing tree is native to mountainous regions in Korea, mainly to the south, as well as areas of Japan. In the wild, they can reach heights of up to 60 feet, but in cultivation, they are typically shorter. 

Transplanting

After bringing your Japanese stewartia home, you’ll want to select an ideal planting spot, making sure to account for its mature size. Dig a hole that is twice the size of the root ball, and add some compost or manure to enrich the soil. 

Backfill the hole until it is just as deep as the root ball so that the trunk doesn’t sit too far under the soil. The top of the root flare should sit slightly above the ground level. Fill in around it with the amended soil, tamp down to remove air pockets, and water in thoroughly. 

Growing From Seed

Growing these from seeds is a challenge that most gardeners don’t embark upon. It requires warm, alternating cool, and warm stratification and specific conditions for germination. It can take seeds up to two years to germinate, so it’s typically passed over in favor of layering or cuttings.

How to Grow

Japanese stewartia is not difficult to grow, and has few serious pest or disease issues. Sunburn is a potential issue that you can avoid with the right planting location. This is a slow grower, which is good to keep in mind as you care for it in the first few years. It will take longer than you expect, but that doesn’t indicate a problem. 

Light

Light is a tricky thing for this tree, as it grows rather large, but full, intense sun can burn the leaves. In cooler climates, it will tolerate full sun, but even in this case, afternoon sun can be harsh.

In warm climates, make sure it’s only in direct sun in the morning, with shade in the afternoon. Dappled sun is appropriate if you have a decent canopy. It will grow well in filtered sunlight. 

Water

Your Japanese stewartia likes moisture, so don’t neglect it in this way, especially in the first year or two. During the first year after planting, make sure to water often and deeply. Watering deeply helps to encourage a deep root system, which anchors the plant before it puts on height. 

Once established, these are more drought-tolerant, but not entirely. They still benefit from occasional watering during times of prolonged dry weather. In fall and winter, be more sparing about water to avoid root rot. 

Soil

You might find this one is too large to grow in a container for long. It prefers soil that is moist but well-drained to combat root rot. It likes a rich, loose mix of sand and loam. Clay and other heavy soil types are not ideal. In terms of pH, the soil needs to be slightly acidic to break down the nutrients it requires. 

Temperature and Humidity

Mild is the name of the game when it comes to climate. This tree thrives in temperatures between 60-75°F (16 and 24°C). If you notice wilting or yellowing leaves, it could be a result of heat stress. Planting in partial shade will help with this.

50% humidity will keep this one happy. You may have some issues in hot, humid climates, but again, some shade will help. High humidity can cause root rot and leaf curl.

Fertilizing

Japanese stewartia doesn’t need a ton of fertilizer, as it should get most of what it needs from the soil. Enriching poor soil at planting time is helpful. A spring application with a balanced, slow-release formula is typically plenty to get your tree growing and blooming. 

If you want to give another application, you can do so about two months later, around flowering time. This will give it a bit of a boost and encourage dense, lush foliage. 

Maintenance

This tree will require more maintenance during its first year, as you’ll want to water it regularly. Just ease up over the winter, or you can end up rotting the roots. Protection from heavy winds is something to be aware of at planting time and going forward. 

Soil pH is another important factor in the health of your plant, as acidic soil breaks down nutrients in a way that makes them more accessible. Top dressing with organic material like compost or manure helps. Mulching around the base will also contribute to richer, more acidic soil over time.  

Pruning is minimal, mostly concerning the removal of dead or damaged limbs and branches. Remove any crossing branches and those that grow through the center of the tree while it’s young. This will increase air circulation to the interior, helping to prevent fungal disease of the foliage. 

Do your pruning in late winter when the tree is dormant, and you have a better view of the interior branches. You can also prune to maintain the size and shape that you desire, though these tend to have a naturally attractive growth habit. 

Propagation

Since propagation by seeds is time-consuming and inconvenient, most growers prefer other methods for Japanese stewartia. Soft-wood cuttings are the most popular method, though layering, and especially ground layering, is also effective. 

Cuttings

To propagate with cuttings, late summer is the ideal time to get started. You want to select soft to semi-hardwood to do the job. 

1. Take cuttings of about three to five inches long from new wood that is either green or just beginning to mature. Select branches that are non-flowering and healthy. 

2. Remove the leaves, except for a few at the top of the cutting. 

3. Scrape the bark from about one inch of the stem at the bottom end, the opposite end from the leaves. This will aid in root development. 

4. Optionally, dip the scraped end into rooting hormone, which also encourages faster, healthier root development. 

5. Fill nursery pots with loose, well-draining soil, and moisten it. One-gallon pots should be large enough to make it through the winter and closer to planting time in the spring. 

6. Insert the cut end of your branches in the soil so that they are standing up straight, and then cover with plastic to hold in moisture and create a greenhouse effect. 

7. Choose a cool, bright location outside of direct sunlight to keep your cuttings over the winter. 

Layering

Layering is another propagation method that works for this plant. Ground layering tends to be more effective than air layering, but either one should be effective with some diligence. 

1. Choose a branch growing close to the ground that you can easily bend so that it touches the ground, if this is not possible. Move on to air layering. 

2. At the place where the branch touches the ground, score around it in two places about an inch apart, and strip the bark from around the branch between those score marks. 

3. Bend the branch to the ground and secure it in place. Landscaping pins work for this purpose, just make sure to find them in the right size for the branch. 

4. Cover the exposed portion of the branch with soil, and cover over with mulch if you desire. The mulch will help protect it and hold moisture in the soil, which is important. 

5. Keep the soil moist in that area until roots develop. 

6. Once substantial roots form, sever the branch on the side closest to the tree, and dig up the new root ball. There, you have a new tree and can plant it independently of the parent. 

Common Problems

While there may be a few issues with pests and diseases, this tree is largely resistant to diseases, and bugs rarely cause major damage. 

Pests

Pests to look out for are common in the garden and include spider mites, scale insects, and aphids. It’s rare for any of these to cause significant damage, unless another compromising factor is also at play.

Try not to treat for pests when the plant is in bloom, to prevent harming pollinators and other beneficial insects. Instead, wait until the blooming period is over and treat with neem oil or another gentle product.

Diseases

These have few issues when it comes to diseases. There are some fungal issues that may crop up, but they are typically mild.

Powdery mildew can be an issue in humid climates. Thinning the interior of the tree will help to improve air circulation. Fungal leaf spot is another issue that typically shows up in humid climates, and the same treatment should mitigate the issue.

Leaf blight and leaf tip necrosis caused by anthracnose are somewhat more serious issues to keep an eye out for. Because these are also fungal diseases, treat them in the same way: increase air circulation and avoid overwatering. 

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