shelter & hedges
Sheltered conditions are needed by many plant species to thrive, including rimu, miro, kohekohe and nikau. Some local species have adapted particularly well to Wellington's windy, cool and sometimes salty conditions: kohekohe, ngaio, mahoe, Melicytus obovatus and Muehlenbeckia astonii. Divaricated, small-leaved shrubs, like the rare and endemic Muehlenbeckia astonii, form a very effective hedge or low shelter belt.
Green shelters bring many benefits
- Green borders look good.
- Hedges and trees provide wind shelter and reduce erosion, noise and pollution while providing privacy.
- Natural shelters moderate light levels and temperature changes, providing habitat for other species.
- Hedges provide corridors for wildlife to travel along.
- Shrubs require no paint work or graffiti treatment.
Single species shelter
Though somewhat unnatural, a single-species hedge can look neat and tidy, and might suit small spaces. Several locally native species can be used, such as akeake (green form) or Dodonaea viscosa, which was one of the more common trees in pre-human times (however in Wellington it could have been introduced by maori). Other ideal species include lemonwood (Pittosporum eugenioides), kohuhu (Pittosporum tenuifolium), akiraho (Olearia paniculata), taupata (Coprosma repens), mapou (Myrsine australis) and the Griselinia species.
The Muehlenbeckia species M.complexa and M.astonii form useful hedges of tangled vines or divaricating branches and are becoming very popular because of their fast growth and response to clipping. They are also tolerant of a wide range of conditions such as salt-laid winds, which make them ideal for coastal gardens. They provide shelter and food for both birds and lizards, but are also important host plants for the native copper butterfly.
Other less known shelter species is rewarewa (Knightia excelsa). Tall and fast growing, rewarewa was one of the trees found growing on the peninsula in 1872, now only reintroduced to the bush and in a few gardens.
The local totara species (Podocarpus totara) is another good example and may be trimmed to a straight hedge. Totara is sometimes considered to be slow growing, however, planted correctly, mulched and with a good amount of fertilizer, totara can grow relatively quickly, if not faster than other species. It answers well to trimming and requires little work, plus its spiky leaves deter trespassers.
For windy and salt-laid sites, taupata (Coprosma repens) and mingimingi (Coprosma propinqua) are ideal species, as are the Muehlenbeckia species of M.complexa and M.astonii.
In a single-species hedge, when one plant dies it can be difficult to replace with a matching plant, and the neat look of the hedge is lost. It can also be difficult to get the replacement to grow due to competition from the larger plants. Also, disease in one plant will usually spread to the whole hedge – a common problem among monocultures.
The mixed shelter is an old method to create a more natural bush edge, and to have food and firewood close by. A number of species are planted together in a wide row, several plants deep. Such a shelter belt offers an attractive look, shelter from the wind and the appropriate selection of species that will attract native birds and other fauna.
Sensitive species generally not suited for shelter can be included in a mixed hedge. A good example is the handsome nikau palm, which provides food for kereru.
Mixed shelter advantages
- Different height requirements can be accommodated.
- Longer lived species can be incorporated, giving a succession of planting.
- The occasional plant failure is not so obvious. The surrounding trees will either fill the gap or self-seeded ones will grow in the space – sustainable and easy.
- Better defences against disease
- One plant’s attributes can cover another’s shortcomings.
- Ideal where space is not a problem.
- Easy to establish and care for.
Plants for shelter
Plants for a pruned hedge
Coastal beach shelter
Coastal gardens can be exposed to severe winds and salt spray. The key to success is to look at what is growing naturally in the area and nearby.
Above the high tide line you find dunes grasses such as spinifex (spinifex sericeus) and golden sand sedge or pingao (Desmoschoenus spiralis). Worser Bay has a few pingao and spinifex growing in pockets between the invasive marram grass. Behind these you find Muehlenbeckia complexa, flax (phormium cookianum) and Oleria. And from there, taupata (Coprosma repens), mingimingi (Coprosma propinqua) and ngaio (Myoporum laetum) and kohekohe (Dysoxylum spectabile).
If you copy this concept and create a shelter on the same basis you will create a wind deflector that will push the coastal winds over beachfront sites.
One coastal species that works well as an appealing hedge is the coastal tree daisy (Olearia solandrii). Its yellowish stems with small, tough leaves make a fine wind-filtering hedge tolerant of extreme coastal conditions. It grows well in full sun and on most soils.
In sheltered bays or moist gullies other species such as ngaio, kohekohe and titoki can grow. Other species tolerant to salt-laid winds can be used in sheltered areas: nikau, rewarewa and griselina broadleaf. Plant in groups if possible.
A note here about nikau, cabbage tree and totara etc, often seen as ‘survivors’ in exposed areas. You may think they are suited to solitary, exposed plantings but usually their former sheltering forest vegetation has been lost. These solitary individuals often look wind battered and are rarely in prime condition due to loss of shelter and moisture.