Japanese meadowsweet is considered by many to be an invasive species due to its ability to spread rapidly, creating a dense thicket or hedge. The species traces its roots to Japan, Korea, and China and was introduced in other areas because of its attractive flowers. Use caution when planting to make sure that this shrub can be managed appropriately.
I. Appearance and CharacteristicsÂ
Spiraea japonica, the Japanese meadowsweet or Japanese spiraea, is a plant in the family Rosaceae. Spiraea japonica is a deciduous, perennial shrub native to Japan, China, and Korea. Southwest China is the center for biodiversity of the species. It is naturalized throughout much of the Northeast, Southeast, and Midwest areas of the United States, and parts of Canada.
Synonyms for the species name are Spiraea bumalda Burv. and Spiraea japonica var. alpina Maxim.
Spiraea japonica is one of several Spiraea shrubs with alternate, simple leaves, on wiry, freely branching, erect stems. The stems are brown to reddish-brown, round in cross-section and sometimes hairy. The shrub reaches 1.2 m to almost 2 m in height and about the same in width. The deciduous leaves are generally an ovate shape about 2.5 cm to 7.5 cm long, have toothed margins, and alternate along the stem. Clusters of rosy-pink flowers are found at the tips of the branches. The seeds measure about 2.5 mm in length and are found in small lustrous capsules.
It is naturally variable in form and there are many varieties of it in the horticulture trade. So far, nine varieties have been described within the species.
A common habitat for S. japonica in general seems to be in riparian areas, bogs, or other wetland habitats. It is found growing along streams, rivers, forest edges, roadsides, successional fields, and power line right-of-ways. It prefers full sun, but can tolerate partial shade. It prefers much water during the growing season; however, it cannot tolerate saturated soils for extended periods of time. It prefers a rich, moist loam, but it can grow in a wide variety of soils, including those on the alkaline side.
II. How to Grow and Care
Sunlight
Japanese meadowsweet needs sufficient light. The more sunlight, the more lush its blossoms. It can put up with short periods of shade, but overly shady environments weakens the photosynthesis process and reduces growth, leading to fewer blossoms and smaller, thinner leaves. The leaves of the variegated variety can lose color and turn green. Space plants 60 to 80 cm apart from each other in order to avoid blocking each other’s sunlight as mature plants.
Temperature
Japanese meadowsweet originated in the temperate and subtropical mountains of the Northern hemisphere. It grows best in regions with distinct four seasons. It’s best grown in temperatures between 10 to 25 ℃ , but can survive as cold as -20 ℃. Besides its excellent cold resistance, it’s also drought- and humidity-tolerant.
Watering
Japanese meadowsweet grows best in moist soil with good water drainage, but can tolerate drought for short periods. Water it in the morning and evening with rainwater or distilled water instead of tap water (tap water contains impurities such as calcium, magnesium, etc., and can compact the soil, decrease air permeability, harm the roots’ breathing, and damage growth and ornamental value).
If it rains for days, don’t water for a short period. When weekly summer rain totals less than 2.5 cm, water once every week. Water thoroughly without leaving standing water. Three days of waterlogged soil can lead roots to rot, leaves to yellow, wither and shed, and the plant to eventually die. If the leaves wrinkle, wilt, and the surface soil turns dry, the plant may be dehydrated, and needs watering promptly. If the leaf tips turn yellow and dry while the surface soil remains damp, it may be overwatered.
Soil
Japanese meadowsweet can grow in barren, saline-alkali soil. It doesn’t require anything specific from the soil, which means you can use all-purpose garden soil. It likes sandy soil that is loose, permeable, and rich in organic matter, but can also live in loamy clay soil. If your region gets a lot of rain, mix 3 parts garden soil and 1 part river sand or perlite to improve the soil’s permeability and water drainage. It grows best in soil with a pH value at 7, a.k.a. neutral soil.
Fertilizing
Apply organic fertilizer in the winter or early spring to help japanese meadowsweet thrive. Apply foliar fertilizer monthly during its growing period, phosphorus-potassium fertilizer 2-3 times during its flower season, and additional organic fertilizers after blooming time. To fertilize, dig a ring-shaped, 10-cm-deep (10 cm deep) ditch around its crown and fill it with fertilizers. This makes it easy for the roots to assimilate. Increase the diameter and depth of the fertilizing ditch as the plant grows. Water adequately after fertilizing to facilitate nutrient absorption.
Planting Instructions
Japanese meadowsweet is intolerant of standing water and can’t be planted on low-lying grounds. Transplant it in early spring and late fall, during its dormancy. Make a tree well 40 to 50 cm wide and 60 to 80 cm deep, and space plants 60 to 80 cm apart. Use either fully decomposed organic fertilizer or those with higher nitrogen and phosphorus content.
When transplanting, move root systems with surrounding soil. The bigger the plant is, the more soil should accompany the roots to raise its survival rate. After planting, cover with a layer of fine soil. Compact the soil and then water the plant. Water once every 7-10 days after the initial watering for 3 cycles, and then return to normal watering frequency as described below.
Pruning
Prune between the end of winter and early spring to trim overlapping, withered, or pest/disease-infested branches. If japanese meadowsweet gets too large, doesn’t have enough growing space, or looks less attractive, prune it severely. Its ability to sprout new branches is relatively strong, and flowers only bloom on new branches. Therefore, there is no need to worry that hard pruning may negatively affect its growth or bloom.
After blooming, cut off the branches that flowered to avoid unnecessary nutrition consumption. This encourages new branches to sprout and prepare to flower. Cover incisions with callus anticorrosion film to encourage healing and prevent bacterial infection.
Propagation
Japanese meadowsweet propagate through seeding or cutting. Ripe seeds can be sown directly and develop into nice-looking plants the very next year. Cutting propagation can be performed in all seasons except winter. Cut off strong branches that sprouted in the current year, dip them in rooting powder, and insert them in perlite or vermiculite, which are excellent at retaining water. Water adequately and mist the branches regularly. It usually only takes two weeks to generate roots in summer.
TransplantingÂ
Ideal times for transplanting japanese meadowsweet range from the pleasant mid-spring to the warmth of early summer. Choose a location with well-drained soil and partial to full sun exposure. If necessary, incorporate organic matter when transplanting to enrich the soil and support healthy growth.
Overwintering
When winter temperatures drop below -10 ℃, protect the seedlings from the cold. Water once before winter and cover seedlings, or build small plastic greenhouses to keep seedlings from frost damage. In two years, Japanese meadowsweet’s cold resistance improves significantly.
III. Uses and BenefitsÂ
Japanese meadowsweet is an ornamental plant that easily grows as a flowering hedge. It is versatile and can be planted as a border, foundation plant, and for erosion control in banks and slopes. It is well suited to cottage gardens and prized for its heat and drought tolerance. There are a range of plants that do well when planted near the japanese meadowsweet, including Japanese barberry, Obsidian coral bells, Lucifer montbretia, and Clematis.
IV. Harvesting and Storage
Japanese meadowsweet’s branches, leaves, and flowers are all highly ornamental and often used in bouquets. After harvest, cut the base of the flowering twigs at a 45° angle with a pair of sharp gardening scissors to maximize the water absorption surface. Place the twigs into a vase filled with clean water quickly to avoid water loss. Cut flowers can last 7-10 days.
