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 and has varying water needs depending on which species is grown. Take care when planting these shrubs in your garden; as the seeds of species Sophora secundiflora are poisonous if ingested. These plants are valued for both their foliage and their showy flowers. Blossoms are sweet-pea shaped and bloom in drooping clusters.

Sophora Species and Varietals

The genus Sophora includes around 45 species and is a member of the plant family Fabaceae. The genus name is derived from the Arabic word sophera, which means 'pea-flowered tree'. Sophora growing zones vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

​Sophora secundiflora (Mescal Bean, Texas Mountain Laurel)
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. Variety 'Silver Peso' has foliage in a silvery-grey, and a white-flowering variety is also available. 

Sophora tetraptera (Kowhair, Yellow Kowhai)
This species is an evergreen or deciduous shrub or tree. It is native to New Zealand and grows well in 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.

Caring for and pruning sophora shrubs

Plant your Sophora shrub in full sun and moderately fertile soil. If your soil is particularly poor, amend with organic matter before planting to improve both drainage and fertility. Water regularly while these plants are establishing themselves in the landscape; at maturity, they are considered drought tolerant and will be able to get by on infrequent deep waterings. Prune to shape and remove dead wood. Fertilizing instructions vary depending on the species; for the most part, applying a balanced, all-purpose fertilizer in springtime is helpful to support flowering and growth for the season.

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
  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. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. 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.
  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 Sophora 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. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
Sophora seeds.

Problems and Pests

These generally hardy plant are susceptible to the following issues:
  • Aphids
  • Spider Mites
  • Powdery Mildew
For more information, see the following links:
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Gallery

Texas Mountain Laurel plants can get relatively large, and can be pruned to grow as a tree with a main trunk.
Kowhia blooms are yellow and profuse.
These trees are beautiful when admired from below, especially when in bloom.

Videos

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Resources

Sophora secundiflora (Texas Mountain Laurel)
How to Grow Sophora
Wikipedia: Sophora
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 607, Sophora
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