Agonis flexuosa makes a handsome addition to the garden, looking good all year round but particularly in bloom, when it bears white flowers along the length of its weeping branches. Extremely drought resistant, this is a much underrated tree that is worthy of greater use in gardens.
I. Appearance and Characteristics
Agonis flexuosa is a species of tree that grows in the southwest of Western Australia. It is easily the most common of the Agonis species, and is one of the most recognisable trees of Western Australia, being commonly grown in parks and on road verges in Perth.
The species is commonly known as Western Australian peppermint, Swan River peppermint or peppermint, and willow myrtle for its weeping habit.
The Noongar peoples know the tree as Wanil, Wonnow, Wonong or Wannang.
Agonis flexuosa occurs mainly as a small and robust tree, usually less than 10 metres tall, although it may grow to 15 metres. It has fibrous brown bark, long narrow dull-green leaves, and tightly clustered inflorescences of small white flowers in the axes. It grows in a weeping habit, and looks remarkably like the weeping willow from a distance. Leaves are narrow and reach a length of 150mm. It is most readily identified by the powerful odour of peppermint emitted when the leaves are crushed or torn.
It flowers between August and December. The fruit is a hard capsule, 3 – 4 mm across, with three valves containing many small seeds.
The tree is used in mass plantings, such as street trees, and has been introduced to Rottnest and Garden Islands near its native region. Agonis flexuosa is an attractive garden or specimen tree in temperate climates. However, care must be exercised in selecting it for small areas, as in a yard setting. Quickly growing, the tree produces a large amount of detritus and its trunk sometimes becomes large and disproportionate to the rest of the tree.
Typically, there are few species that grow under A. flexuosa trees, as the leaf litter can suppress understorey species.
A. flexuosa and var. nana respond well to pruning and they are often pruned back to the main trunk to promote new growth and to keep a tidy and dense canopy. Without pruning, the canopy can become thin. The species, in some circumstances — such as when grown on rocky, terraced terrain — can grow buttress roots, but seldom does in flat, sandy areas.
A. flexuosa trees can also have a twist or spiral effect in the bark of their main trunks that increases with age, usually evident in seedlings.
It is not a species that is used for bonsai.
II. How to Grow and Care
Watering
The water requirements of Agonis flexuosa can vary depending on the specific cultivar and the conditions in which it is grown. However, on average, the tree requires around 10-20mm of water per week, depending on weather conditions and the maturity of the tree. It is important to note that newly planted trees will require more frequent watering to help establish their root systems, and mature trees can tolerate longer periods of drought.
Fertilizing
Agonis flexuosa should be fertilized to promote healthy growth and maintain overall tree health. However, It is generally not recommended to fertilize a newly planted Agonis flexuosa right away. It is best to wait until the plant is established and has developed a healthy root system before applying fertilizer.
When a plant is newly planted, it is in a delicate state and its root system is still adjusting to its new environment. Applying fertilizer too soon can be stressful for the plant and can cause damage to the roots. This can lead to the plant being less able to absorb the water and nutrients it needs to survive.
It is also important to note that too much fertilizer can burn the roots and cause damage to the plant, it is best to avoid over fertilization.
It is recommended to wait for about 4-6 weeks after planting before fertilizing Agonis flexuosa. This will allow the plant time to adjust to its new environment and develop a strong root system. Once the plant is established, you can begin to fertilize it according to the specific requirements of the cultivar and the growing conditions.
If using a slow release fertilizer Agonis flexuosa should only need to be fertilized once a year, typically in late winter or early spring before new growth begins. It is important to follow the manufacturer’s instructions and not to over fertilize as this can lead to leaf burn and other damage.
If you are trying to encourage faster growth or a more dense hedge then more regular fertilization may be needed. Read the label/instructions of the fertilizer you have chosen to find how long the fertilizer lasts (some may say 6-8 weeks, others 3 months or even 6 months). Reapply the fertilizer after your previous application has run its course.
Pruning
Agonis flexuosa should be pruned as needed to maintain its shape and size. This can vary depending on the specific cultivar and the conditions in which it is grown.
Larger varieties can be pruned annually, biennially or as needed to remove any damaged, diseased or crossed branches. Due to their weeping habit it is most common to need to lightly trim some weeping branches so that the tree can be walked under without the dropping leaves brushing against people.
Smaller varieties like Agonis flexuosa ‘Nana’ can be used as a hedge, to maintain a hedge ‘Nana’ would need to be hedged every 6-12 weeks once it has reached the desired size of the hedge.
The best time to prune Agonis flexuosa is typically in late winter or early spring before new growth begins. Pruning at this time allows for easy visibility of the tree’s structure and makes it easier to identify any damaged or diseased branches. Additionally, pruning during the dormant season can help to promote new growth and better overall health of the tree. If maintaining a hedge or specific shape then prune as needed.
Pests and Diseases
Common Pests
Common Pests of Agonis Flexuosa: Agonis flexuosa is generally considered to be pest-free, but some common pests that can affect the tree include:
- Scale insects: These are small, hard-shelled pests that attach themselves to the leaves and branches of the tree. They can cause leaf yellowing, wilting, and dieback.
- Mites: Spider mites are tiny, spider-like pests that can cause discoloration and stunted growth. They can also cause webbing on the foliage.
- Caterpillars: These can cause defoliation and damage to the tree. Aenetus dulcis – Australian Lepidoptera caterpilars have been known to bore into the stems of Agonis Flexuoa
- Sawfly: These insects can cause leaf damage, and heavy infestations can cause defoliation.
It’s important to keep an eye out for these pests and take action if you notice them on your Agonis flexuosa. Regular inspections can help you identify problems early, before they become too severe.
Common Diseases
Common Diseases of Agonis Flexuosa: Agonis flexuosa is generally considered to be disease-free, but some common diseases that can affect the tree include:
- Myrtle Rust
Myrtle rust is a fungal disease that can cause significant damage to Agonis flexuosa, also known as West Australian Weeping Peppermint. The fungus (Austropuccinia psidii) affects plants in the Myrtaceae family, which includes Agonis flexuosa.
When the fungus infects Agonis flexuosa, it causes the leaves to develop bright yellow or orange spots. These spots can also appear on the stems and branches of the plant. As the disease progresses, the leaves may become distorted, curled and wilted, and the plant may become stunted.
The fungus can also infect the flowers, causing them to become discolored and fall off prematurely. This can lead to reduced fruit production and overall plant health.
One of the most noticeable symptoms of myrtle rust on Agonis flexuosa is the formation of small, bright yellow or orange spores on the undersides of the leaves. These spores can be easily spread by wind or water, making it easy for the fungus to infect other plants in the surrounding area.
In severe cases, myrtle rust can cause the death of infected plants. It is important to take action quickly if you suspect that your Agonis flexuosa has been infected with myrtle rust.
To prevent myrtle rust from damaging your Agonis flexuosa, it is important to keep the area around the plants free of debris and to avoid overcrowding the plants. Regularly inspecting the plants for signs of infection and taking action as soon as you notice any symptoms.
If you suspect that your Agonis flexuosa is infected with myrtle rust, it is important to seek the advice of a professional horticulturist or plant pathologist as soon as possible. They can help you determine the best course of action to save your plant and prevent the spread of the fungus.
- Root Rot
This is a fungal disease that can cause yellowing and wilting of leaves, as well as dieback of branches. It is caused by overwatering or poorly drained soils.
Agonis Flexuosa do not need much water and do best in free draining soil. If you are having this issue, reduce watering days to once per week to let the soil dry out between watering days.
It’s important to keep an eye out for these diseases and take action if you notice them on your Agonis flexuosa. Regular inspections can help you identify problems early, before they become too severe. Proper cultural care like proper watering, good drainage and proper pruning can help prevent these diseases.
III. Uses and Benefits
Agonis are generally considered to be well-suited to coastal conditions. It is salt-tolerant and can withstand coastal winds, making it a good option for coastal gardens or landscaping.
Agonis flexuosa is an excellent option for use as a street tree as it responds well to trimming under power lines, and it can also be utilized for screening off areas to provide privacy.
The Noongar peoples used the plant leaves as an antiseptic; sapling trunks were used as spear shafts and digging sticks.
Find Where to Buy the Best Willow Myrtle (Agonis flexuosa)
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