While hedges are pretty low maintenance, like all vibrant living things, they do require some TLC. Instant hedges do need water and a little food and enjoy an occasional tickle up. But they are not keen on weeds or pesky pests. A little love goes a long way, so read how you can show your Living Walls instant hedge that you care.
For effective establishment in the landscape, instant hedges and pleached screens, like all advanced grade plants, will require deep watering in their first two growing seasons (spring to mid-autumn) and over extended windy and or dry periods, even once established. In very light soils or areas where root growth will be restricted (e.g. hedges in containers or planter boxes), a permanent irrigation system is required. Container mix that has been allowed to dry out becomes hydrophobic (repels water) and will require more water to re-wet.
Regularly monitor the irrigation when newly planted or as the seasons change, to ensure that your hedges are watered adequately, i.e. neither over nor under-watered. Stressed plants, i.e. those receiving insufficient irrigation or those sitting in saturated soils, can suffer root death and become prone to insect pests and diseases.
Drip irrigation is the best method for irrigating instant hedges. For instant hedge irrigation, we recommend and can supply Flow Regulated Landscape Drip Line. The drip line evenly delivers water to the root zone where it is needed. Roll out the dripline on top of the original rootball close to the trunks, and secure using the pins provided. Plug into your garden hose when it is time to water, add a timer if desired or integrate into your irrigation system. We do not recommend leaky hose or sprinklers. Consistent hand watering at the root zone for very short hedge lengths or a small number of containers may be sufficient. Install drippers for Pleached Screens and container planting. Purchase drippers from your local garden supply retailer.
You may still need to irrigate your hedge on or soon after rainy days. Light rain is unlikely to sufficiently penetrate dense hedge foliage to wet the root zone adequately.
While establishing in its new home, water your instant hedge deeply, one to three times a week depending on hedge variety, soil type, environmental conditions and season. This watering encourages deep rooting that anchors the instant hedge and helps it become established and more self-sufficient. Adjust your watering for your environment, the season (i.e. more frequently in the growing season, less in winter), and as the hedges grow taller and or broader. In a hot, windy area, your hedge may require 25% more water whereas, in a cool sheltered spot with heavy soil, your hedge could require a lot less. More water may also be necessary where competing plant/tree roots are close to the hedge root zone. The soil should be moist to touch at about 5cms from the surface.
As a rough guide, the following volumes/times are a good starting point for deep watering
– 100L hedges require approx 7.5 litres of water per lineal metre per watering. 7.5L equates to around 1 hour if using the Flow Regulated Landscape Drip Line supplied.
– 70L hedges require approx 4 - 5 litres of water per lineal metre per watering. 4L – 5L equates to 30 – 40 minutes if using the Flow Regulated Landscape Drip Line supplied.
– 25L hedges require approx 2.5 litres of water per lineal metre per watering. 2.5L equates to around 20 minutes if using the Flow Regulated Landscape Drip Line supplied.
All hedges benefit from regular feeding. Fertilising will help with establishment, vigour, health, and quality of your instant hedge. On the other hand, excessive or incorrect fertilisation may cause excessive succulent growth that may be susceptible to cold damage, drought and diseases. We recommend feeding your hedge in early spring and again in mid-summer with a complete slow-release granular NPK (nitrogen, phosphorus and potassium)-based fertiliser, such as Nitrophoska or Triabon®. These fertilisers are readily available from your local garden supply store. Sprinkle the fertiliser onto the soil surface at approx 50 – 100 grams per metre of hedgerow depending on hedge size. An average handful is around 50 grams. Avoid contact with the leaves or trunks as the fertiliser may burn. With dense foliage, it is helpful to water-in the fertiliser using a hose. Once your inground hedge has established and reached your desired height and width you can cut the fertilising down to once a year, in early spring. Continue to feed hedges in containers and planter boxes twice a year.
Once planted, we strongly recommend adding a good layer (say 5cm total depth) of well-composted, organic mulch. Maintain this level each spring, after you have fed your hedge. Mulch helps with moisture retention, soil conditioning and weed suppression. Ensure that the mulch is well clear of the trunks and lower branches.
Formative trimming (trimming newly planted rows of individual plants into a hedge) is the key to establishing great hedges. Fortunately, by purchasing a Living Walls instant hedge, the formative trimming has been done for you.
The timing and frequency of maintenance trimming depend on the plant species as well as your desired finish. Generally,trimming your instant hedge a minimum of 2 – 3 times during the growing season (spring to mid-autumn) will suffice. This trimming encourages new growth and helps ensure that foliage remains dense. If necessary, perform any harder cutbacks in spring, while the hedge is most actively growing. If you want your hedge to grow taller than when purchased, it will still require some trimming on top, to encourage dense and even growth. Leave trimming of flowering hedges until after flowering, and fruiting hedges until after fruiting. Trimming your hedge in the evening or on an overcast day will minimise leaf scorch. We try to avoid trimming our hedges while the birds are nesting too!
The choice of hedge trimming equipment comes down to personal preference (and level of fitness!). Hand shears are great for short runs and make the tidiest cut, particularly on hedges with larger leaves. For speed or longer hedgerows, battery-powered trimmers win hands down. We use battery-powered trimmers in the nursery.
Cut the sides first. Vertical sides suit low hedges, but they shade out lower growth in taller hedges. Trim your Living Screen or Living Boundary hedges so that the sides taper inwards from bottom to top, 5° to 10° from the vertical. This angle allows sunlight to reach the lower branches and helps prevent leaf loss. Angled trimming is particularly important for sun-loving plants such as Pittosporums. Don’t be afraid to set up string lines along the hedge to act as a guide. Hedges may well be ‘self-healing’, but it will still take time for mistakes to grow out.
Once your hedge has reached your desired height and width, only trim the new shoots/growth. Trimming encourages more of the buds on the remaining wood to develop.
You can improve the establishment and growth of newly planted instant hedge by eliminating competition from weeds, especially grasses. Grasses compete for water and soil nutrients. They will retard the hedge’s root growth if present. Turf and weeds should be removed from/controlled along the base of the hedge. Use mulches to help control weeds and conserve moisture.
Contact herbicides, such as those containing glufosinate or organic herbicides (such as Hitman®) are active against a wide range of grass and broadleaf weeds and not taken up by roots. Avoid contact with green parts of the hedge, including immature bark as damage may occur. We do not recommend using systemic herbicides such as glyphosate (e.g., Roundup®) close to your hedge or any desirable plants.
Where possible, we avoid spraying our hedges. Healthy, vigorous hedges can generally cope with pests and diseases when they occur on a minor scale. But our landscaped gardens are artificial situations, and the build-up of pests and diseases may reach undesirable levels requiring treatment. Choosing an instant hedge variety suited to your local soil and climatic conditions will alleviate most pest and disease issues, as will good drainage, site preparation, and hedge maintenance.
We’ll briefly cover a few problems that can sometimes affect popular hedging plants in New Zealand. Our main reference sources are Managing Pest and Diseases by Rob Lucas, Craig Potton Publishing; and New Zealand Novachem Agrichemical Manual, published by Agrimedia Ltd.
Psyllids are small insects; the adults look like winged aphids. The juvenile stage has a thin, flat, shell-like covering that makes them look like scale insects. Symptoms include tiny ‘lumps’ or blistering on the new growth of Pittosporum and Syzygium hedges in spring and summer. The shoots and leaves are resistant to infestation once the new growth has hardened. Consequently, the long-term effect of psyllid on an established hedge is not usually significant.
Before spraying your hedge, check that the psyllids are still alive. Live psyllid is cream, effectively treated psyllids have browned off, empty indentations mean they have left the plant. Control psyllid by 2 – 3 sprays of an appropriate systemic insecticide during spring and summer if required. We use imidacloprid (available from Agpro) which also controls aphids, mealy bugs, scale, thrips, whitefly and other sucking insects on ornamentals, roses and vegetables. Please read the label in full and contact Twining Valley Nurseries for suggested application rates. An organic option is regular applications of spraying oil (e.g. Eco-oil®) following the label recommendations. The insecticide options available in retail stores require a direct hit (contact) on the insect. As psyllids are under the leaves, spraying needs to be directed up and into the dense foliage and repeated as necessary.
Once treated, or if they are dead/no longer present, trim off the worst affected unsightly leaves as these don’t improve. Monitor new growth for signs of infestation. Clear away the trimmings as they may harbour live psyllids.
Most scales are 2-3mm long insects which have hard coverings, and they are often mussel shaped. Scale insects fix themselves to leaves and stems and suck sap. Infested leaves turn yellow and are often covered with copious quantities of sticky honeydew on which sooty mould grows. Nymphs called ‘crawlers’ are tiny mobile juvenile scales and disperse over plants or are carried further afield by wind, birds and insects. Later nymph stages are immobile and form hard protective coverings.
Several plant varieties, such as Corokia, Syzygium, Camellia, Ilex, and Citrus, can be attacked by scale insects. Parasites attack many scale species, and this may be sufficient to keep populations down to acceptable levels. Where chemical control measures are necessary, we use the same pesticides as for psyllid control.
Thrips are another tiny insect which is barely visible to the naked eye. Adults are usually black, and nymphs are cream. They infest and damage foliage and flowers of many ornamental plants including hedges of Photinia, Citrus, and Bay. Thrips commonly cause silvering on the upper sides of leaves and deposit tiny, brown, treacle-like excreta on the undersides.
Thrips are relatively easy to control with 2-3 systemic insecticide sprays over the summer months. Thrips favour warm, dry, sheltered conditions, so avoid using susceptible hedges in these environments.
A large number of fungal parasites can cause root rot in plants. IThe most common root diseases in hedging plants are the water moulds phytophthora and pythium. As these diseases progress, lower leaves droop, turn yellow then brown, and may fall off. Upper leaves wilt, and sometimes the complete plant dies. In other cases, one part of the plant dies and leaves the rest apparently healthy. Many plants infected with phytophthora develop a symptom known as ‘collar rot’ – a ring of black stained tissue at the base of the stem. The severity of symptoms and the speed of disease development depend on the plant’s ability to produce new roots and withstand the possible water shortages resulting from root loss. Phytophthora disease in susceptible plants is most prevalent in heavy soils that dry out in summer and are very wet in winter.
Avoid planting susceptible plants (e.g., Griselinia, Michelia, Olearia, and Corokia hedges) in such positions, or improve these soils by mulching well with organic matter and improving drainage. Incorrect watering and fertilising may also exaggerate the problem.
If disease symptoms develop, you may protect healthy plants by spraying and or drenching the soil with the systemic fungicide, phosphorous acid (e.g., Foli-R-Fos® or Foschek™), at recommended label rates. Remove severely infected plants, improve drainage and treat soil (by drenching fungicide) before replanting.
Myrtle rust is a fungal disease that affects plants in the myrtle family such as popular hedging plants Syzygium spp., feijoa and bottlebrush. Because the fungus infects soft, new growth, and is most virulent during warmer months, avoid regular trimming during summer months if possible. Fortnightly sprays of a protectant copper fungicide may help in areas where Myrtle rust is present. Curative fungicides are available to landscape/garden maintenance contractors.