Coprosma is one of the largest genera of flowering shrubs in New Zealand, with about 90 recognized species. The leaves of some species give off a pungent and unpleasant odor when crushed. Coprosma is native to Australia, New Zealand, and countries in the Pacific Ocean.
Species of this perennial shrub, also known as the mirror bush, are grown for use as a specimen tree and as an evergreen hedging plant.
Coprosma is a genus, but to most people, it is the species Coprosma repens that represents the plant known as Coprosma. This low-growing shrub grows widely along the coast in New Zealand, where it is well known by its Maori name Taupata Taupata.
It is a common sight in seaside towns and used as hedging where there is a high salt content in the air.
Because one or two species have leaves that exude a foul-smelling odor when crushed, it became known as the dung bush by the botanists on Captain Cook’s second voyage.
|Common names||Mirror bush|
|Height||Up to 15 feet (4 ½ m)|
|Width||Up to 10 feet (3 m)|
|USDA Plant Hardiness Zone||Zones 8 to 11|
|Native to||New Zealand|
|Flower colors||Green, white|
|Plant specific features||Evergreen, tough, resistant|
How to Plant and Grow a Coprosma Bush
Where to Plant
Because of its tough and salt-resistant nature, a coprosma is ideal for harsh, windy coastal locations where salt spray makes it difficult to grow many plants.
But, it will grow equally well in a container, or in open ground, providing it is placed in a sunny position.
It is a tender plant, but providing you don’t have frost or snow (or you can provide protection from these elements if you do), you can plant a coprosma shrub.
When to Plant
Coprosma is also known as New Zealand laurel and the ideal planting time is between May and June, before the onset of the heat in Summer.
Coprosma Shrubs Care and Maintenance
The coprosma will do best if it is planted in well-draining soil. This is really important because if its roots are left in waterlogged soil for a prolonged period, the shrub will probably die due to root rot.
Neutral, or slightly acidic soil is the best choice and is reasonably rich in organic matter. If you are planting the coprosma in a pot or container, then you can use compost that is designed for ericaceous plants such as rhododendrons and azaleas.
A newly planted mirror bush should be watered well immediately after planting. A thorough watering at this stage will settle the soil around the shrub’s roots and help to conserve moisture at the base of the plant for some time.
The shrub mustn’t be allowed to dry out during its first growing season, as it has to develop its root structure. At least once a week, provide deep and thorough watering, continuing to water whilst the excess drains away.
Once established, however, after a year or so, then a coprosma is not a thirsty plant. Only occasional watering will be required.
When it is established, it is essential not to overwater, as the plant is prone to root rot. However, some watering may be necessary during long hot, and dry spells.
It is a good idea to provide a bit of extra feeding in the Spring. This will encourage plenty of new growth and keep the plant full and dense.
A newly planted shrub will probably already have fertilizer in its container, but if you have planted a bare-rooted specimen, then you need to fertilize it.
Choose a fertilizer that is high in phosphorous (the “P” in an N-P-K fertilizer composition) and apply it at the manufacturer’s recommended dosage. Phosphorous encourages root growth.
An established coprosma can also benefit from an annual application of fertilizer. Shrubs require annual feeding, but trees only every two or three years because they have deeper root systems.
Don’t apply fertilizer late in the growing season. Fertilizer encourages new growth that may not have time to harden off sufficiently to withstand the colder temperatures of winter.
The best planting site for a coprosma is somewhere that receives part shade and part sunlight. This will give the best results, with the most prolific flowering, color, and growth.
Partial shade will provide the shrub with some protection from the strong afternoon sun.
You may be able to plant it underneath a tall tree with overhanging branches.
Pruning and Repotting
To keep a neat and tidy habit, prune the mirror bush twice a year. This will keep the plants compact and dense in the center.
Pruning will keep your plant clear of damaged and dead wood, which, if left on the plant, can attract pests and encourage disease. Removing dead wood from the center of the shrub will increase airflow and lessen the risk of disease. Dead wood can be removed whenever you spot it.
If you prune your shrub in the Spring, you will encourage new growth and this will promote increased flower production, as well as healthy and colorful foliage.
Late summer pruning should be avoided as it will encourage new growth at the end of the growing season. The new shoots will not have sufficient time to toughen up before the onset of the cold temperatures.
If you need to transplant or repot the coprosma, the best time to do this is in the Spring, before new growth appears.
The easiest method of propagation is when the shrub does the work for you! Coprosma branches have a tendency to lean downwards and touch the ground.
These stems will layer themselves; if necessary, you can give them a helping hand by placing a weight on the spot where the branches touch the soil.
You can also take cuttings from mature wood. The best branches to use for cuttings are low-growing ones. Remove most of the leaves of the cuttings, leaving the top pair.
Then, dip the ends into hormone rooting powder and insert the cuttings into pots filled with potting compost mixed with sand or a mix designed for succulents. Water and cover the pot with plastic to retain the moisture.
You can leave the cuttings to root in a sheltered light location, but out of direct sun. Keep the soil moist but not wet.
Once they have rooted, allow a further couple of months before transplanting them, to ensure the roots are sufficiently developed to survive the move.
Pests and diseases
The flea beetle is endemic to New Zealand where coprosma grow. Adult beetles feed on the leaves of the shrub.
The most common problem with coprosma is root rot. This is caused, together with other fungal diseases, by the shrub being left in wet soil, or by overwatering.
Make sure that the soil drains well and if you have had issues with fungal disease in the past, clean the soil before replanting to remove the spores in the soil.
Other pests that can pose minor damage are aphids and spider mites. These are unlikely to cause serious damage and can be treated with an organic insecticide.
Temperature and Humidity
Coprosma is also known as the Mirror plant because of its very shiny, glossy, thick foliage, that protects the plant from salt when it grows near the coast.
It does well in full sun, but if you are in a hotter region, then the coprosma will need some protection from the heat of the strong afternoon sun.
Coprosma is recommended for growing in USDA zones 9 to 11 and is frost hardy to -8° C.
This is a plant that doesn’t like to be overwatered, and it is important that once established, it is only watered occasionally.
Other Uses for Coprosma
The coprosma leaves and shoots have been used in the past by Maori for medicinal purposes, to treat kidney, bladder, and gastric troubles.
Berries, once ripe, were used to make an infusion and the stems are rich in dye properties.
Types of Coprosma You Can Grow
Coprosma Pacific is different from other species and was developed in Europe. This species is quick growing, and extremely colorful – all year long. It is fast-growing and retains a bushy habit.
Coprosma Pacific won’t grow more than one meter high or wide. It is low-maintenance and vigorous. These characteristics make them ideal for container growth, as well as for borders and hedges.
Coprosma repens “Marble Queen” is evergreen, and has beautiful variegated foliage. The leaves are green but marbled with creamy-white streaks. This is also known as the variegated mirror bush plant.
Mirror bush, New Zealand laurel, Shiny leaf, Taupata, Looking Glass bush … so many names for the same plant! But one thing is sure, a coprosma is an excellent addition to your borders if you want a shrub that you can just plant and forget about!
*image by MartinaUnbehauen/depositphotos