It is very obvious that many of the selections of hedge plants introduced into New Zealand over the years have become environmental disasters – gorse, privet, acmena, and berberis to name just a few. And there are others, like Buxus, which I’m sure you all love. But it has a dreadful smell, the smell of cat’s piss after rain. It also gets rust, a lovely rust which makes it go nice and red, but people keep planting it and it dies off and they plant another lot.
Then there are various conifers which have been getting fungus and large areas of dieback. A hedge cutter trims these hedges; he cuts some branches which are covered in spores, then goes next door and spreads the spores and eventually does himself out of a job.
With this in mind we at Joy Plants have been planting New Zealand native trees and shrubs in various situations to get some idea of how hardy they are – wind hardy, frost hardy, drought or wet tolerant, and what their ultimate size will be without pruning. New Zealand has an amazing array of shrubby trees that fit the bill as hedging – examples are pittosporum, muehlenbeckia, myrtaceae, coprosma, myrsine, melicytus, corokia, conifers and many daisy family plants, all of which are readily available. Some of these have been used over a number of years for windbreaks but they and other species have very rarely been used for garden hedges or in ornamental situations.
Choose slow-growing but easy to maintain plants
Many are perhaps slower to grow but they are ideal in home gardens as they require no or very little pruning and training, not like this other thing that’s around at the moment – Remuera privet. Griselinia that is. It’s a horrible thing for a hedge! It grows to 15 to 20 metres high, you’ve got to cut it every fortnight and all the leaves get cut in half. It has not even got a nice leaf for a hedge.
Among the New Zealand species we have been trialling are about seven species of Pittosporum.
Pittosporum obcordatum was once one the the rarest pittosporums to find. It grows easily from seed or cuttings to about 3m, has a mass of bronze twigs and makes a great windbreak. It is suitable for most soils and will tolerate wet situations. It gets covered in flowers and if very wind proof. I believe these plants grew right throughout New Zealand at one time but our forefathers chopped them all down. They’re frost hardy, water hardy and will even grow in a swamp. What more could you ask?
Pittosporum turneri grows to 3m tall, is very narrow, has silvery foliage and grows well in shady spots.
Pittosporum anomalum is my favourite and grows very slowly to 1m, makes tight ‘hedgehog’ growth and has pale cream flowers. It takes only five years to germinate from seed and, although it’s easy from cuttings, you do get prickles.
Pittosporum crassicaule grows very slowly to only 50cm and has tight growth and beautiful black flowers. They don’t smell during the day but at night the sweet smell is amazing! Tiny seed pods hang on the the tree for three to four years before they ripen and then they take up to seven years to germinate. It’s ideal for alpine gardens.
Pittosporum rigidum grows to 1m, is narrow and has dark twigs. Pittosporum umbellatum (below) is another amazing wind-hardy plant. You can see them all along the Coromandel Coast and up north. It has beautiful umbels of flowers in pink white and cream. It’s a bit tricky to propagate from cuttings but no problem from seed. All the above pittosporum have perfumed flowers at night and all grow from cuttings or seeds, although they can take some time to strike.
Melicytus, which can look like buxus species, can be trimmed into small hedges…or topiary turkeys or elephants as the mood takes. Forms of Melicytus obovatus have been very good. Some reach 1.5m, others only 50cm. I’ve been selecting species of Melicytus from the northern South Island and southern North Island for many years. I believe it’s a better plant than buxus. Makes a great hedge, doesn’t need much cutting and grows to 2 metres or more.
Melicytus crassifolius makes an excellent tiny hedge and also has several forms and some hybrids which are well worth trying. They provide food for lizards and moths etc, and all are very long lived.
Myrsine: South Island forms of Myrsine divaricata will take damp soils and freezing temperatures, also salt winds. They are slow-growing and tangled and twiggy as shrubs but will grow into larger trees over time. Myrsine divaricata Poor Knights, now known as Myrsine aqualonia, is also great for coastal and drier, windy sites.
A must mention is the related Elingamita johnsonii – it makes a great hedge for salt-wind coastal conditions. It’s a small shrubby tree but needs good drainage and no frost.
Sophora Dragon’s Gold is a candidate for hedging. It produces masses of gold flowers.
Coprosma – a huge number of these are great for coastal, windy conditions but some may need trimming to keep them controlled. For the taller narrow windbreak to 3-4m, Coprosma virescens is possibly the best with orange or pink stemmed twigs and great fruit for birds. It rarely needs trimming. Coprosma rhamnoides with its many forms and leaf colours has great potential and will tolerate shade and a range of sites. Coprosma rhamnoides ‘Mercury Green’ is a selection from Joy Plants that doesn’t get mildew like ‘Mangatangi’, and has a great shape to be trimmed as a hedge.
Coprosma lucida is a good hedge plant. It comes in various forms and has beautiful red berries which are fabulous brid food. It grows to a nice shrub and you don’t need to cut it for five or six years. It will make a brilliant windbreak will grow in sand, can handle salt winds and insects eat the leaves which makes it look even better.
Coprosma crassifolia is a beautiful shrub with a gorgeous shape and lovely white undersides to the leaves giving it a ghostly appearance.
Coprosma tenuicaulis will grow readily in the shade. A nice, tall plant, it can be trimmed into a windbreak or hedge.
Muehlenbeckia – Muehlenbeckia complexa will soon cover any space but with training and trimming can make any old fence into a work of art. Muehlenbeckia astonii can be used for two-metre cloud-shape hedges.
Metrosideros – Metrosideros perforata inter-planted with Metrosideros carminea will make a nice flowering hedge with not much trimming or can be planted to cover any badly made wall.
Ozothamnus species grow to 1-2m. These bushy shrubs will grow in the most dreadfully windy, salty, sandy sites with a range of grey or golden leaf forms and masses of tiny daisy flowers for native bees. Most of the daisy family are tricky in the nursery situation and many get root rots in summer due to over-watering. But they are fine when planted out and provide plenty of flowers over their silvery foliage in many cases.
There are several tree species that are worth a mention: Corynocarpus laevigatus, Hoheria angustifolia, Libocedrus, Metrosideros excelsa and Metrosideros robusta, Podocarpus totara and Streblus. These are not for all sites due to the large size they can grow to over time, but many can be trained and trimmed quite happily.
Carpodetus serratus has a flat, low-growing prostrate form that’s ideal for a low hedge. It’s brilliant for lizards, butterflies and insects and is also a good wetland plant.
Streblus heterophyllus, the small-leafed milk tree flowers from mid spring to late summer and has red berries from spring through to autumn.
Hoheria sexstylosa is a really nice plant and a great host plant for native weevils, Some of our rarest weevils love the seeds of this tree. Bees love it too. It makes a brilliant hedge and probably live 15-20 years.
[PART 1 of ‘Hatch On Hedges’ is republished with the kind permission Commercial Horticulture – New Zealand’s Nursery Industry magazine. It is based on a presentation Terry Hatch gave to the IPPS Conference in Nelson in early 2015. All photos are by Terry and Lindsey Hatch]