Zanthoxylum piperitum
( zan - tho - ZI - lum pi - PER - i - tum )
At-A-Glance Information
Commonly called Japan Pepper, Japanese Prickly Ash or Sansho, this species of of deciduous, aromatic shrubs and trees needs full sun and moderate water. They are native to Japan and Korea and have a dense growth habit to 8-20 feet tall and wide, with handsome dark green foliage that sometimes yellows in fall. Flowers are green and insignificant, blooming in April and May, and aromatic red fruits follow in autumn. These plants are hosts of the Swallowtail Butterfly. The seeds are used as seasoning in Japan, and the peppery-tasting leaves are used in Japanese cuisine as well. The genus Zanthoxylum includes 250 species and is a member of the plant family Rutaceae. Japan Pepper grows well in zones 6-9 and 14-17. To find your zone, click here: Zone Map.
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Caring for and pruning Zanthoxylum piperitum shrubs
Plant Sansho in full sun to partial shade; they will perform and produce better the more sun they receive. Well-draining soil is essential, and these plants prefer a slightly acidic to neutral pH (around 5.5 is usually adequate). Amend soil with plenty of organic material before installing. Water regularly while these plants are getting established and during especially hot or dry periods. Lessen waterings in cooler weather. These plants are not heavy feeders, but if they seem to be struggling due to a nutrient deficiency, a feeding with a balanced, slow-release fertilizer can bring them back up to optimal functioning. Apply a layer of mulch around the base of the plant to suppress weed growth, regulate soil temperature, and increase soil moisture retention.
Prune while they are dormant in wintertime, removing wayward and crossing branches. These plants can tolerate periods of light frost, but are not generally very cold-hardy. Provide protection during prolonged freezing temperatures to avoid damaging the plant and affecting the harvest for the following year. Sansho plants can be used as bonsai subjects or grown in containers. Ensure that potted soil mix is well-draining and that it has adequate holes on the bottom for drainage. Container-grown plants will need more frequent waterings.
Harvesting Zanthoxylum piperitum Shrubs and Trees
Leaves and berries on these trees and shrubs have a unique, citrusy flavor (these plants are in the same genus as Citrus) and are often used in traditional Japanese recipes. Young leaves and shoots are used in soups and to garnish grilled fish, but are not palatable to everyone. Immature green berries are commonly blanched and salted, or simmered in soy sauce to create the condiment tsukudani, and mature berries are ground up and used to flavor a multitude of dishes.
Prune while they are dormant in wintertime, removing wayward and crossing branches. These plants can tolerate periods of light frost, but are not generally very cold-hardy. Provide protection during prolonged freezing temperatures to avoid damaging the plant and affecting the harvest for the following year. Sansho plants can be used as bonsai subjects or grown in containers. Ensure that potted soil mix is well-draining and that it has adequate holes on the bottom for drainage. Container-grown plants will need more frequent waterings.
Harvesting Zanthoxylum piperitum Shrubs and Trees
Leaves and berries on these trees and shrubs have a unique, citrusy flavor (these plants are in the same genus as Citrus) and are often used in traditional Japanese recipes. Young leaves and shoots are used in soups and to garnish grilled fish, but are not palatable to everyone. Immature green berries are commonly blanched and salted, or simmered in soy sauce to create the condiment tsukudani, and mature berries are ground up and used to flavor a multitude of dishes.
Propagation
Zanthoxylum piperitum 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 or tree, follow the instructions below:
Propagating Zanthoxylum piperitum by Cutting
Propagating Zanthoxylum piperitum by Seed
Propagating Zanthoxylum piperitum 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. 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.
- In 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 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 Zanthoxylum piperitum 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. 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.
- Harvest your seeds. The seed pods on Caesalpinia 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.
- Soak seeds in lukewarm water for 24 hours and then set them out. Fill a sealable plastic bag with peat moss and moisten, and then place the seeds in the bag, and the bag in the refrigerator for three months. After this period has passed, take the seeds out and plant them.
- 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 can take up to 1 year 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.
Problems and Pests
Zanthoxylum piperitum is susceptible to the following pests and diseases:
- Aphids
- Scale Insects
Gallery
Videos
Learn about these wonderful trees and shrubs.
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These plants produce edible parts used in many dishes.
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Learn how to create a bonsai with Japan Pepper Tree.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 659, Zanthoxylum piperitum (Japan Pepper, Shiso)
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