Styphnolobium

( stiff - noh - LOH - bee - um )

At-A-Glance Information

This genus of small deciduous trees and shrubs includes species that require full sun to partial shade and moderate water to perform well in the landscape. These plants are native to China and the Americas, and have a moderate growth rate, reaching up to 50 to 75 feet tall and just as wide at maturity. Young wood is smooth and dark greyish green, and older bark becomes rough and deeply furrowed. Foliage is green to blue-green and pinnately compound, giving it a ferny or tropical look. It yellows in fall before falling. Flowers are white, cream-yellow, or soft pink and bloom in drooping panicles in late spring and summertime. These trees will bloom best in regions with long, hot summers. Use these trees and shrubs in the garden as ornamental specimens, urban shade or street trees, in lawns, or to bring pollinators into the landscape. Take care when planting these trees in the landscape, as plant parts (especially seeds and pods) are toxic to humans and pets if ingested.

Styphnolobium Species and Varietals

Styphnolobium is a genus in the plant family Fabaceae, and includes 9 species. The plants in this genus are related to those in Cladrastis (Yellow Wood). Chinese Pagoda Tree grows best in USDA hardiness zones 4-8 or Sunset growing zones 2-24. To find your zone, click here: Zone Map.

Styphnolobium affine (Eve's Necklace, Eve's Necklacepod, Texas Sophora, Pink Sophora, Necklace Tree)
This species is native to Oklahoma, Texas, Arkansas, and Louisiana in the United States, and reaches up to 30 feet tall when mature. It forms a deciduous large shrub or small tree with green, divided foliage and white to maroon-pink fragrant flowers. Seed pods that follow resemble strings of beads, hence the common name for the species.

Styphnolobium japonicum (Sophora japonica) (Japanese Pagoda Tree, Pagoda Tree, Chinese Scholar Tree, Huai, 槐, Huai shu, 槐树, Enju, エンジュ)
This species is native to China and is an introduced species in Japan. It forms a large multi-stemmed shrub or small tree to between 35 and 50 feet tall. Older specimens can reach up to 75-80 feet tall. Leaves are green and divided, and flowers are white, sometimes marked with cream or green. Cultivars of this species include 'Regent' (with dark green leaves and a faster growth rate), 'Pendula' (with weeping branches to 15-25 feet), 'Columnaris' (also called 'Fastigiata', to 40 feet tall and 15-20 feet wide), 'Princeton Upright' (with a narrow branching structure), 'Millstone' (pictured, with a rounded to oval canopy) and 'Violacea' (with unique pink and white tinted flowers).

Caring for styphnolobium

Take care when planting these trees in the landscape, as plant parts (especially seeds and pods) are toxic to humans and pets if ingested. Styphnolobium trees prefer to be planted in a location that receives full sun (between 6 and 8 hours of direct sun every day), though they can also grow in places that get partial shade. They will flower and grow the fastest in full sun exposure. Make sure that there is enough space to accommodate the tree at its full size in the space chosen; these trees can reach up to 30 to 50 feet tall and just as wide. These trees produce deep taproots, so there should be no pipes or other barriers to root growth under the planting area. They do not transplant well, so make sure that the planting site is chosen carefully to avoid the need to move the tree later on. Soil should be well-draining. If local soil is heavy or clayey, amend with plenty of organic material before installation. Styphnolobium prefers a soil pH of between 4.5 and 8.0 (acidic to alkaline).

When planting, ensure that the root flare (the point where the roots start to flare out for root growth is slightly above the soil surface. For newly planted trees, soil should be kept consistently moist. Apply a 2-3 inch deep layer of mulch around the base of the tree after installation. After the first few years in the ground, these trees are considered moderately drought tolerant, and will be able to get by on only deep waterings during extended dry periods of the year. Avoid frequent, shallow waterings (lawn water). These trees do not need fertilizing other than a yearly application of organic compost around the base of the tree. Pruning is also minimal, and should be completed in late wintertime or early springtime before new growth pushes out for the year. At this time, remove dead, damaged, or diseased growth as well as any crossing branches. These trees have a naturally attractive shape, and do not need additional shaping. Avoid heavy prunings, as it can cause excessive sap bleeding. If pruned correctly, these trees can survive in the landscape for 100 to 150 years or more before needing to be replaced. Regular pruning is crucial for these trees to address their tendency for forming weak crotches that are susceptible to storm damage and early failure.

Propagation

Styphnolobium 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 Pagoda Tree, follow the instructions below:

Propagating Styphnolobium 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 late 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 to 8 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 Styphnolobium ​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. Seeds are contained inside of the pods that dangle from branches after flowers have faded. These trees are hermaphroditic, meaning that flowers have both male and female parts. They are insect pollinated. Pods are ready to be harvested when they begin to fall from the tree naturally; there are about 4 to 6 seeds within each pod. Remove seeds from the pods and place them in a bowl of lukewarm water for 24 hours to soften the seed coat.
  3. Seeds can be sown in spring or fall. 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 7-14 days from sowing.
  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.
Styphnolobium seed pods dangle from attachments where flowers once bloomed. They contain 1 to 6 seeds each.

Problems and Pests

Styphnolobium plants can be susceptible to developing issues with the following pests and diseases in the landscape:
  • Leafhoppers
  • Aphids
  • Leafminers
  • Scale Insects
  • Fungal Cankers
  • Twig Blight and Dieback
  • Powdery Mildew
  • Root Rot
  • Verticillium Wilt
For more information on these pests and diseases, including how to treat and prevent them, consult the following pages:
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Gallery

Weeping Styphnolobium trees have beautiful forms when mature.
Styphnolobium are popular urban shade and street trees.
Flowers are similar to those of other genera in the Fabaceae family.

Videos

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Resources

Styphnolobium japonicum
How to Grow and Care for Japanese Pagoda Tree
Wikipedia: Styphnolobium
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 617, Styphnolobium japonicum