Pterostyrax

( teer - oh - STYE - racks )

At-A-Glance Information

This genus of deciduous trees and large shrubs includes species commonly called Epaulette Trees that need full sun to partial shade and regular water to perform well in the garden. These eastern Asian native trees and shrubs make interesting garden specimens; their white, frilly flower clusters appear in springtime and last into early summer and leaves are deep green. Use Epaulette Trees as feature or specimen plants in the landscape, near patios or walkways, or in open woodland borders for their fragrant springtime flowers.

pterostyrax Species and Varietals

The genus Pterostyrax is a member of the plant family Styracaceae and includes just four species. The plants in this genus are closely related to those in Styrax (Snowbell), Halesia (Silverbell) and Chionanthus (Fringetree). Epaulette Tree grows well in USDA hardiness zones 3 through 9 or Sunset growing zones 3-10 and 14-21. To find your zone, click here: Zone Map.

Pterostyrax corymbosa (Little Epaulette-Tree, Shrubby Epaulette-Tree, Epaulette Tree, Asagara, 麻殻, Asagai)
This Japanese native tree is not as widely grown as other species. Flower clusters are broad and individual flowers are bell-shaped and have protruding stamens. Fruits that follow are downy and winged. These trees can reach up to between 20 and 40 feet tall when mature, and often form multi-stemmed, rounded, or fan-shaped canopies. This species is suited for USDA hardiness zones 5-9.

Pterostyrax hispidus (Pterostyrax hispida) (Epaulette Tree, Fragrant Epaulette Tree, Asagara, ōba-Asagara, オオバアサガラ, Bristly-Fruited White-Spicy Tree, Hairy-Fruit White-Acrid Tree, Máo Guǒ Bái Xīn Shù, 毛果白辛树)
This species, native to Japan and China can be grown as either a single- or multi-trunked tree reaching 20-30 feet tall and just as wide. Leaves are light green above, gray-green underneath. White flowers appear in puffy, slightly fragrant clusters. Fruits are small, furry and grey, and hang on through the winter months; attractive on otherwise bare branches.

Pterostyrax psilophyllus (Small Epaulette Tree, Epaulette Tree, Bái Xīn Shù, 白辛树, 刚毛白辛树, 鄂西野茉莉, 裂叶白辛树)
Endemic to central China, this species is currently threatened by habitat loss. These deciduous small trees reach up to 50 feet tall, and have green foliage. Flowers are white, and hang off of branches that are 4-6 inches long. These trees are suited for growing in USDA hardiness zones 4-8.

Caring for pterostyrax

Epaulette Trees prefer a place in the landscape that receives full sun to partial shade. In warmer climates, make sure these trees (especially when young) are getting some protection from the hottest rays of afternoon sun, which can scorch foliage and branches and stress out the tree. These plants will flower more profusely in full sun, and need hot, sunny summertime weather to flower well. Soil should be slightly acidic to neutral, with a pH of between 5.5 and 7.0. Substrate should be well-draining. If local soils are heavy or overly clayey, make sure to amend the planting site with plenty of organic material and/or sand before installing. Apply a thick layer of mulch around the base of trees to suppress weed growth, increase soil moisture retention, and help to regulate soil temperatures. Water young plants regularly during the growing season. Established trees are considered to be somewhat drought-tolerant, but do appreciate consistent moisture during the drier months of the year.

Once established, these trees do not need much in the way of pruning. In late winter or early springtime, prune back dead, damaged, diseased, or crossing branches and thin out the canopy. A light shaping can also be completed after flowering has ceased for the year. Apply a feeding with an organic compost in springtime around the base of trees and shrubs. This will typically be sufficient to support growth and flowering for the year, but if trees seem stunted or are struggling, they may benefit from an additional feeding with a balanced, slow-release fertilizer in spring, as well. Avoid excessively fertilizing these trees and shrubs, as they will push out a lot of leafy foliage growth at the expense of flowering. These trees can be expected to survive for 40 years or more in gardens, and reach full physical maturity and maximum size in 10 to 20 years.

Propagation

Pterostyrax can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Pterostyrax tree or shrub, follow the instructions below:

Propagating Pterostyrax by Cutting
  1. Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
  2. In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
  3. Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots. 
  4. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Pterostyrax by Seed
  1. Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
  2. Harvest your seeds in fall. The seed pods are relatively easy to find; they hang onto the flower panicles after female flowers have faded, and will dry out and turn brown when ready to let go of seeds. Collect as many as possible, place them in a paper bag, and bring them indoors. They can be stored in a cool, dark, dry place for about a year.
  3. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2 to 3 months from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
  4. Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Pterostyrax fruits are small, dry drupes with a beak-like style. Each individual pod contains 1 or 2 fleshy seeds.
Pterostyrax seed pods (drupes).

Problems and Pests

These trees have no serious insect or disease problems. For information on common garden plant issues, consult the following pages:

Gallery

These shrubs have a beautiful, pendulous branching structure.
A young Pterostyrax shrub.
Pterostyrax flowers give off a pleasant, sweet refreshing scent compared to Citrus or mild Jasmine.

Videos

All about the Epaulette Tree.

Resources

Pterostyrax - Growing Guide
Wikipedia: Pterostyrax
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 539, Pterostyrax