Coprosma, Mirror Plant: Planting and Cultivation

botany

The Coprosma is a small evergreen bush from the Rubiaceae family, much like the Gardenia. The genus Coprosma comprises 90 species native to Oceania, particularly New Zealand, along with numerous hybrids that have recently entered the European horticultural market. The bush has a notably dense, upright, and compact habit. Within 4 or 5 years, it forms a bush reaching approximately 50 cm to about 1.50 m in height, depending on the variety. In its native habitat, this bush can grow up to 3 m tall.

Coprosma nitida, botanical plate circa 1840

The Coprosma stands out for its glossy, varied, and changing foliage that persists through winter, brightening the garden year-round. The flexible, ramified stems bear small, opposite, ovate to lanceolate leaves, leathery and shiny on top, matte underneath. They are marked by a lighter midrib. Leaf colours vary by cultivar, ranging from soft green to chocolate brown touched with bright green or pink, through red, bronze, or purple. Some varieties display multicoloured foliage, such as the Coprosma ‘Evening Glow’. With each season change, their colours evolve. Their vibrant hues are lighter in summer, darkening and turning purple under the influence of cold. The overall effect is a shimmering bush that reflects light, earning it the nickname “mirror plant.”

The summer flowering is insignificant. From August to September, it appears as clusters of small, greenish-white tubular flowers with prominent stamens. The Coprosma is a dioecious plant, meaning fruiting only occurs if male and female plants are placed side by side. If this condition is met, the flowers are followed by globular, vermilion-orange berries that delight birds. Highly decorative, these scarlet drupes harmonise with the foliage, often tinged purple by autumn.

Coprosma kirkii ‘Variegata’, Coprosma ‘Rainbow Sunrise’, and on the right, fruits of Coprosma brunnea

Main species and varieties

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Planting

Where to Plant Coprosma?

Originating from New Zealand, Coprosma retains a certain sensitivity to cold and a preference for mild climates. Not very hardy, it begins to suffer at temperatures as low as -3 to -5°C (sometimes -8°C in extreme cases, in very well-drained soil), and prefers mild winters. Hybrid varieties often show greater resistance to diseases and cold. It can only be grown in the ground in coastal gardens spared from severe frosts. In regions with harsh winters, it should be grown in pots on the terrace or balcony throughout the growing season before being moved to a sheltered spot for winter in a cool, bright, and minimally heated room.

Very tolerant of salt spray and drought once established, Coprosma is an ideal plant for coastal gardens. It thrives in very sunny or lightly shaded locations in the southern part of the country and prefers light, well-draining soils, neither too dry nor too moist, and free from lime. It tolerates poor soils.

With its dense, colour-changing foliage, depending on the variety, it can be planted in borders, rockeries, low hedges, or at the forefront of a flowering or mixed hedge that is well-protected. Its compact growth makes it perfectly suited to container cultivation.

Coprosma montana (© Forest and Kim Starr)

When to Plant Coprosma?

Coprosma is best planted in spring, from April to May, avoiding periods of frost or drought.

How to Plant the Mirror Plant?

In the Ground

Space plants 1m to 1.50m apart for larger varieties and 0.50m to 0.60m for dwarf Coprosmas. Drainage must be excellent. In water-retentive soil, opt for planting on a mound.

• Dig a planting hole twice the diameter of the root ball
• Add a 10cm drainage layer (pumice or gravel) at the bottom of the hole if your soil is clayey
• Mix garden soil with turf and some horticultural sand
• Plant without burying the collar
• Firm the soil and water
• Monitor watering for the first two years

Container Cultivation

Choose compact varieties like ‘Mini Mac’.

• Place a generous layer of drainage (gravel or clay pebbles) at the bottom of the container
• Plant in a mix of leaf mould, heather soil, and river sand
• Water, then maintain regular watering
• Place the pot on a terrace sheltered from scorching sun and strong winds

Maintenance, pruning and care

The Coprosma requires little care and maintenance. Ensure it does not lack water during its first summers to aid establishment. Once well-established, it can do without watering in summer in most regions, except during prolonged droughts. Potted specimens have greater water needs; water once a week throughout the growing season.

In colder regions, when the first frosts arrive, remember to move pots indoors to a bright, frost-free room.

Pruning is not essential; it involves cutting back dead stems, those damaged by winter frosts or faded flowers between April and August. This helps maintain a lovely bushy and compact shape and stimulates the production of new shoots. Prune using pruning shears, always sparingly.

Coprosma repens ‘Marble Queen’ (© Cultivar 413)

Diseases and potential pests

The Coprosma is hardy. It may occasionally suffer from scale insect attacks, especially when grown in a greenhouse: spray rapeseed oil to suffocate the pests.

Multiplication

You can propagate the Coprosma by taking semi-woody stem cuttings in summer.

• Take stems measuring 8 to 10 cm
• Remove the lower leaves, keeping only those at the top
• Plant the cuttings in a bucket, using a moist mixture of river sand and compost
• Keep them covered until rooting occurs, then protect them from frost throughout the winter
• Transplant the cuttings into the ground or into pots in spring

Associate

Coprosmas are perfect for adding a permanent splash of colour, more or less flashy depending on the cultivar, to any composition. With their glossy and ever-changing foliage, they play wonderfully with light, brightening up dull areas of the garden throughout the seasons. They are invaluable in a coastal garden.

At the edge of a lush flower bed, the shorter varieties will find their place alongside a mix of vividly coloured perennials: Rudbeckia, Echinacea, Salvia greggii ‘Mirage Burgundy’, phormiums, daylilies, or dahlias, all punctuated with stipas for a delicate and wild touch. The small blue flowers of the sages will make excellent companions.

Remarkable specimens like ‘Fire Burst’ can be planted in a bed of compact bushes composed of green-foliaged plants (Lonicera nitida), golden (golden oregano, Chamaecyparis obtusa ‘Kamarachiba’, Berberis thunbergii ‘Aurea Nana’, Mexican Orange Blossom), or purple like that of the Berberis.

They can blend into low hedges with any type of bush. In autumn, their colourful foliage will harmonise beautifully with smoke bushes or Sacred Bamboo, Japanese maples, and spindle trees with mahogany hues. They easily accompany other acidophilous plants like the Cercidiphyllum japonicum (Katsura Tree).

Coprosma ‘First Burst’ (© Leonora Enking), Choisya ternata ‘White Dazzler’, Berberis thunbergii ‘Admiration cov’, and Chamaecyparis obtusa ‘Karamachiba’