Reeve’s Spiraea (Spiraea cantoniensis)

Bridalwreath spirea (Spiraea cantoniensis) is a plant species native to China. Bridalwreath spirea is generally cultivated as an ornamental plant used on the borders of gardens. Spiraea cantoniensis is also known by the common names Bridalwreath spirea, Double White May, and Cape May.

I. Appearance and Characteristics

Spiraea cantoniensis, the Reeve’s spiraea, bridalwreath spirea, double white may, Cape may or may bush, is a species of plant native to China, belonging to the rose family Rosaceae.

It is a deciduous or semi-evergreen shrub that reaches a size of 1–2 m height, with many thin branches, arched, flexible and glabrous. The leaves are alternate, simple, small petiolate, with 2–6 cm long green lanceolate, elliptical-rhomboidal or slightly ovate lamina, with 3 nerves parallel from its base, irregularly crenate-dentate in its distal half. The leaves may turn a yellowish red color in autumn. Blooming in spring and snow white in color, its flowers are hermaphroditic, actinomorphic, of ± 1 cm diameter, arranged in axillary carimbos, each with 5 free sepals, 5 white petals, numerous stamens shorter than the petals. The fruit is a poly-follicle, with 3-5 plurisemined carpidia (follicles).

Reeve's Spiraea (Spiraea cantoniensis)
Spiraea cantoniensis tgrauros CC BY-SA 2.0

It is used as a screening or bordering plant alongside a fence line or as a conspicuous feature plant. May bushes prefer a full sun to partly shaded position with well drained soil, forgiving both light frost, wind, heat, poor soils and drought. It is generally best grown in cooler climates with protection from the hot afternoon sun which can cause leaf burn. Furthermore, the plant should be mulched and well-watered. Trimming and fertilization may be needed after flowering to keep a wedged growth habit and boost productive flowering in the next season.

II. How to Grow and Care

Sunlight

Bridalwreath spirea 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

Bridalwreath spirea 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

Bridalwreath spirea 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).

Reeve's Spiraea (Spiraea cantoniensis)
Spiraea cantoniensis kz04 Krzysztof Ziarnek, Kenraiz CC BY-SA 4.0

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

Bridalwreath spirea 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 bridalwreath spirea 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

Bridalwreath spirea 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

Reeve's Spiraea (Spiraea cantoniensis)
Spiraea cantoniensis joka2000 CC BY 2.0

Prune between the end of winter and early spring to trim overlapping, withered, or pest/disease-infested branches. If bridalwreath spirea 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

Bridalwreath spirea 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.

Transplanting

The most favorable season for bridalwreath spirea is spring (S1) to early summer (S3), essentially when warmer weather starts. This promotes optimal root establishment and growth. Choose a location that’s well-drained and partially shady. It’s crucial to adequately water bridalwreath spirea after transplanting to reduce transplant shock. Do remember, patience is key with bridalwreath spirea, they might take time to adapt to the new environment.

Overwintering

Reeve's Spiraea (Spiraea cantoniensis)
Buquê-de-noiva (Spiraea cantoniensis). China e Japan native mauro halpern CC BY 2.0

In rainy seasons, prevent waterlogged soil; long-term standing water can cause root rot. Digging a drainage ditch is helpful. 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, bridalwreath spirea’s cold resistance improves significantly.

III. Uses and Benefits

Bridalwreath spirea is a very common border or screen shrub prized for its waterfall of white spring blossoms. It is beautiful enough to grow as a specimen, but its bushy and manageable habit makes it perfect along fence lines or as a hedge in Asian or xeriscape gardens. Hostas, salvias, and hydrangeas make for great companions.

IV. Harvesting and Storage

Reeve's Spiraea (Spiraea cantoniensis)
File:Starr-090519-8118-Spiraea cantoniensis-flowers-Kula-Maui (24588168889).jpg Forest and Kim Starr CC BY 3.0

Bridalwreath spirea’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.

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