Sophora

sophora

( so - FOR - uh )

At-A-Glance Information

This genus of evergreen and deciduous trees and shrubs, also known as Kowhai, needs full sun to partial shade in the landscape. These plants are valued for both their foliage and their showy flowers, varying widely in size and habit. Blossoms are sweet-pea shaped and bloom in clusters. Species are native to Asia, Europe, Australasia, the Pacific Islands, and the Americas. Use Sophora plants as ornamental accents, erosion control, or soil remediation plants in coastal, drought-tolerant, pollinator, wildlife, or informal gardens. Take care when planting these shrubs in your garden; as the seeds of some species are poisonous to humans and pets if ingested.

Sophora Species and Varietals

The genus Sophora includes around 45 species and is a member of the plant family Fabaceae. The plants in this genus are related to those in Maackia and Baptisia (False Indigo). The genus name is derived from the Arabic word sophera, which means 'pea-flowered tree'. Sophora growing zones vary depending on the species cultivated. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Sophora cassioides (Sophora macnabiana) (Pelú, Chilean Pelú, Chilean Kowhai, Mayu-Mote)
This species is endemic to central and southern areas of Chile, and form shrubs or small trees. Individual plants can reach up to 52 feet tall when mature. Flowers are golden-yellow, and bloom simultaneously with leafout in springtime. They are followed by seed pods. Leaves are compound and green. This species is suited for USDA hardiness zones 8-10 and is considered invasive in New Zealand.

Sophora chysophylla (Māmane, Mamane)
Native to Hawaii, these shrubs or trees can reach up to 50 feet tall, and produce yellow flowers in winter and springtime. They have greyish bark and an irregularly rounded crown as trees. Branches are golden brown, and leaves are pinnately compound and green. This species is suited for growing in USDA hardiness zones 10 through 12.

Sophora flavescens (Shrubby Sophora)
These plants are native to India, Japan, Korea, and Russia, and reach about 6 feet tall when mature. They form shrubs with floppy stems that are covered in soft hairs when they are young. Flowers are light yellow, white, purple or red, blooming from June through August. Fruits follow and remain on the plant from July through October.

Sophora secundiflora (Dermatophyllum secundiflorum)(Mescal Bean, Texas Mountain Laurel, Frijolitos, Grape Kool-Aid Tree)
This species takes the form of an evergreen shrub or tree and grows well in zones 8-16 and 18-24. It is native to Texas, New Mexico and areas of northern Mexico. It reaches 15-25 feet tall and 10-15 feet wide, and is very slow growing. Leaves are glossy and dark green and flowers are violet-blue and fragrant. Blooms pop from the middle of winter through early springtime. Poisonous bright red seeds are contained in silvery grey to brown seed pods after flowers fade. Great for large hedges or background foliage, and can also be trained into a small tree that is wonderful on patios, lawns, or as a street tree. This species does well in alkaline soil and likes the heat. Needs moderate water. Cultivar 'Silver Peso' (also called 'Silver Sierra') has silver-grey foliage.

Sophora stenophylla (Fringeleaf Necklacepod, Silvery Sophora)
These plants are native to the southwestern United States, and are perennial sub-shrubs. They reach up to 16 inches tall, and have lacy leaves and purple-blue flowers that bloom from April through May. These plants spread by underground roots, forming colonies. Fringeleaf Necklacepod plants are best suited for USDA hardiness zones 4-8.

Sophora tetraptera (Kowhair, Yellow Kōwhai, Large-Leaved Kowhai, North Island Kōhai)
This species is an evergreen or deciduous shrub or tree. It is native to New Zealand and grows well in USDA hardiness zones 8-11 or Sunset growing zones 15-17, reaching 15-20 feet tall and wide. Leaves are silky grey on top, reddish underneath, and flowers are golden yellow. Likes humid climates, and needs regular water to perform well in the landscape.

Caring for sophora

Take care when planting these shrubs in your garden; as the seeds of some species are poisonous to humans and pets if ingested. Plant Sophora in a space in the landscape that receives full sun; ideally, they appreciate between 6 and 8 hours of sun each day for the best blooms. When these flowers are grown in less light, they will not flower as profusely. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.0 and 7.5 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention.

Water new plantings regularly as they establish a strong root system in their new home. At maturity, these plants are considered drought tolerant, able to get by on rainwater alone with supplemental irrigation during extended periods of drought. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. Sophora can be expected to survive in the landscape for a few decades to a century before needing to be replaced, depending on the species cultivated.

Propagation

Sophora 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 shrub, follow the instructions below:

Propagating Sophora by Cutting

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.
In summer or fall, 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 semi-hardwood 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.
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.
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 Sophora by Seed

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.
Harvest your seeds. The seed pods on Sophora plants are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Sophora seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting shrub you want. Place your seeds in warm water for twelve hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
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. 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.
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.

Seeds are borne in seed pods that dangle from branches after flowers have faded. Each contains between 3 and 10 seeds.

Sophora seeds are hard and oval-shaped.

Problems and Pests

Certain species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. These generally hardy plants are susceptible to the following issues in the landscape: