The griselinia hedge is excellent for creating boundaries and providing privacy. It’s a hardy evergreen shrub that is gaining in popularity. The leaves have are shiny and have an apple green color all year round.
The hedge is resistant to most diseases, and is drought and water tolerant. However, there are a few things that can affect griselinia, despite it’s hardy reputation.
Griselinia Hedge Basics
Griselinia hedge is also known as the New Zealand broadleaf or New Zealand privet. As the name suggests, it’s native to New Zealand. The scientific name for the hedge is Griselinia littoralis.
It’s an excellent choice for coastal or wind-swept areas. It’s low maintenance and very forgiving, making it a good option for busy gardeners.
It grows about 1 foot a year under good conditions. It can grow up to 10 meters, or 32 feet, tall. However, it’s usually used for hedges between 1 and 5 meters, or 3 and 15 feet, in height.
4 Common Griselinia Hedge Problems
Here are the 4 most common griselinia hedge problems you may encounter as well as what to do in each case.
1. Root Rot
Root rot is caused by a fungus, also known as water mold. The culprit is typically Phytophthora. It thrives in wet soil conditions. If the soil is constantly wet, it allows the fungus to proliferate. This fungus can then find its way onto the roots of the griselinia.
Root rot is often caused by overwatering, but poor draining soil or heavy rains can also lead to root rot.
The first sign of root rot is yellow leaves. The leaves may also fall off. If root rot isn’t treated, dieback or stunted growth will occur. Over time, root rot can be deadly, even for the hardy griselinia.
Root rot damages the roots, causing them to become brown and mushy. The damaged roots can’t bring in the needed water and nutrients, which eventually causes damage or death to the plant.
Treating Root Rot
The most effective way of treating root rot is to remove the plant from the soil. You can then trim away any damaged roots, rinse in a bleach solution to kill any remaining fungus, and replant is soil that isn’t contaminated with root rot.
With plants like the griselinia hedge, this isn’t often possible or feasible.
If you catch root rot early, you can treat it with trichoderma. This is a beneficial fungus that can kill other fungus organisms which cause root rot.
If the root rot is widespread, the only way to eradicate it is with a strong fungicide. Choose a type that fights blight. Spray it on the leaves of the plant and the roots. You can repeat these treatments one month later.
2 months after the original application, you can apply trichoderma to help prevent root rot from reoccurring.
2. Leaf Spot
The good news is that leaf spot will not cause your griselinia serious damage. However, it can be an aesthetic problem and does affect the health of your hedge in a minor way.
Leaf spot can be caused by a virus, bacteria, or fungus. Despite the different origins, leaf spot diseases have similar affects on plants.
Just like root rot, leaf spot diseases prefer wet conditions. Heavy rains, high humidity, and windy conditions can all spread or encourage leaf disease.
Leaf spot causes brown spots on the leaves. Cell death occurs in these areas. The damaged leaves can’t create photosynthesis, but most cases of leaf spot don’t affect a large number of leaves. This means that it creates only a small amount of stress on the tree.
However, leaf spot is concerning if it affects a large amount of leaves. If you notice moderate or complete leaf loss, you have a serious case of leaf spot.
Treating Leaf Spot
There are some things you can do to prevent and treat leaf spot. First, remove any fallen leaves before winter snow or rainfall. The fungus on these leaves can survive the cold months, and reinfect the hedge the next spring.
Overcrowding plants can also encourage leaf spot to spread. Prune the hedge to ensure proper airflow and light penetration.
Avoid spraying water on the leaves, since leaf spot thrives in wet conditions. Allow the soil to dry between waterings. You can have a sample tested to determine the exact strain of leaf spot disease.
However, many fungicides can treat the problem. These include Bordeaux mixture, zineb, chlorothalonil and Captan. These can treat a wide variety of leaf spot diseases.
3. Honey or Bootlace Fungus
Honey fungus can be deadly for your griselinia hedge. It spreads underground, allowing it to attack plant roots. The symptoms of honey fungus include die-back, pale foliage, and bleeding or cracking bark. Eventually, the fungus can kill your hedge.
Honey fungus can create fruiting bodies above ground, known as mushrooms. These may look like harmless mushrooms. However, this honey colored mushroom is an indication of honey fungus.
These distinctive mushrooms may be easy to identify, but they don’t always occur with honey fungus. It can also thrive beneath the ground, wreaking havoc while remaining unseen.
Other signs of honey fungus include white ‘mycelium’. It can also create bootlace fungus, or rhizomorphs. This is where the name bootlace fungus comes from. They appear red or purple, and eventually turn black.
Treating Honey Fungus
The only way to kill honey fungus is to remove the affected plant and the surrounding soil. Burn the plant to prevent the spores from spreading to other areas. You’ll need to wait 6 months to a year before replanting in the area.
You may have to remove surrounding plants as well, as the fungus may have spread to them.
Summing It Up
The griselinia hedge is very hardy and isn’t susceptible to many diseases and pests. However, it’s not completely problem free.
It is susceptible to root rot. It needs well-draining soil. Avoid overwatering, as this can lead to root rot.
If leaf spot disease occurs, fungicides can kill the fungus or bacteria causing the disease. Honey fungus is more difficult to manage. However, not all types of honey fungus are detrimental to your griselinia hedge. Some will only attack or harm weak plants, while others can be fatal to healthy plants as well.