Troubleshoot these 10 typical issues in your native garden
Native plants have a reputation for being indestructible, which makes it more confusing when one starts to fail. The causes tend to repeat, though. Most problems trace back to the roots, to watering or to the timing of pruning. Some come down to a specific pest.
These are the questions we get asked most often. Other typical and regularly seen problems are covered in our guide to common issues with native plants.
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1. Why is my boronia dropping its leaves?
Leaf drop is a sign of a stressed boronia and the stress is usually at the roots. Brown boronia (Boronia megastigma) is highly prone to root rot and often dies suddenly. A root zone that dries out does the same damage as one that stays waterlogged, which is why boronia is renowned for being tricky to grow.
How treatable is it? Often it is not, because a boronia can die suddenly once root rot sets in. Getting drainage and moisture right matters more than any fix.
What to do
| Step | What to do |
|---|---|
| 1 | Check that the soil drains freely and the root zone stays evenly moist. If water sits around the roots, the position is wrong for this plant, so choose a better drained spot for any replacement and plant it slightly raised. If the soil dries out, water deeply rather than often and lay 7 to 10 centimetres of coarse mulch, pulled back 5 to 10 centimetres from the stem. See mulching natives. |
| 2 | Check that the plant is not exposed to the warm westerly winds of summer. If it is, plant any replacement in a more sheltered position. |
| 3 | In our experience snails will also chew boronia foliage, so check the leaves for chewing and look for snails on and around the plant. |
| 4 | Keep moisture even with a terracotta olla, which waters the root zone without wetting the surface. |
| 5 | Do not prune a stressed plant. Once it recovers, prune lightly and regularly after spring flowering. |
| 6 | If it dies, replace it with a grafted plant where one is available. Our boronia growing guide covers species by climate zone. |
2. Why has my dichondra gone brown and holey?
Brown patches in dichondra (Dichondra repens) can come from heat, dryness, frost, foot traffic or a fungal leaf disease. In a dry Perth or Adelaide summer it browns off unless it is watered. In cooler districts a hard frost can brown it but it should recover in spring. Lawn weed and feed products also kill dichondra.
A leaf disease caused by a fungus has been recorded on dichondra in Victoria. Small brown or black flea beetles also feed on dichondra, although a few do little harm to a healthy plant.
How treatable is it? Dryness, foot traffic and watering problems can be corrected, and frost browning recovers in spring. If a fungus is the cause, there is not a well-documented treatment for it.
What to do
| Step | What to do |
|---|---|
| 1 | Give plants that have dried out or been scorched by heat a good deep soak. |
| 2 | Keep new plantings regularly watered for their first three months. |
| 3 | In Perth and Adelaide, expect to irrigate through summer. |
| 4 | Keep the soil moist but not soggy and water again once the top few centimetres have dried. |
| 5 | Avoid stepping on it while it is in a stressed state. |
| 6 | If the browning is blotchy and keeps spreading, it may be a sign of fungus. |
| 7 | If frost caused the browning, be patient. The patches fill in again in spring. |
Other groundcovers for a similar spot are covered in our guide to low-traffic lawn alternatives.
3. Why are the leaves on my lilly pilly lumpy and distorted?
Lumpy, pimply leaves are the work of a psyllid (Trioza adventicia) that sucks sap from the new growth. Its feeding leaves oval bumps on the upper surface of each leaf and matching dents underneath. Susceptibility varies widely by cultivar.
How treatable is it? It is hard to treat. Spraying is not recommended because the damage shows after the psyllid has done its work, so choosing less affected species from the outset is the most reliable answer.
What to do
| Step | What to do |
|---|---|
| 1 | Do not rely on spraying. By the time the damage shows it is usually too late and chemical control impacts other life in the garden. |
| 2 | Water regularly in dry weather as stressed plants are more prone to insect attack. |
| 3 | Give a slow-release native plant fertiliser once a year in spring. |
| 4 | When buying new plants, choose from the less affected species. |
4. Why did a healthy, established native plant die suddenly?
When an established plant collapses without warning, the cause is usually in the roots. One possibility is Phytophthora dieback (Phytophthora cinnamomi), a soil-borne water mould that rots the roots of susceptible plants. Once the roots rot they cannot take up enough water and nutrients and infected plants can die very quickly.
The pathogen thrives in warm, moist soil and spreads as spores in water, soil and root-to-root contact.
How treatable is it? There is no cure for Phytophthora dieback. Phosphite increases a plant's resistance but does not cure an infected plant, so prevention is the real answer.
What to do
| Step | What to do |
|---|---|
| 1 | Buy plants from accredited nurseries. |
| 2 | Keep mud from vehicles and shoes out of the garden. |
| 3 | Where water collects, plant slightly raised and use coarse mulch and plants suited to the site. Gypsum only improves drainage in clay that is sodic or dispersive. |
| 4 | Phosphite is a fungicide that increases a plant's resistance to infection but does not cure an infected plant. It is injected into trees or sprayed on shrubs. |
| 5 | Where a plant has died, replace it with a resistant species. |
5. What are the balls on my wattle tree?
Hard, round swellings on the stems, leaves, flower buds or seed pods of a wattle are galls caused by rust fungi of the genus Uromycladium. They can be green or brown and are often dusted with brown powder, which is the fungus producing its spores. On a hedge wattle they reach about 4 centimetres across, while on larger species they can grow much bigger.
The fungus spreads on the wind to other wattles. For most trees the galls are not a death sentence. Severe infections can kill a tree within two to three years but most survive much longer.
How treatable is it? We found no verified treatment for galls in home gardens. Most trees survive for a long time, although a severe infection can kill a tree within two to three years.
What to do
| Step | What to do |
|---|---|
| 1 | Unfortunately there is not a verified treatment for galls in home gardens, so it is best to wait and watch. |
| 2 | If the galls spread across the plant and it declines, ask an arborist or a plant diagnostic service to identify the problem and advise. |
Our wattle growing guide covers species by climate zone.
6. Why will my native plant not flower?
A plant that is short of light, sitting in poorly drained soil, growing in the wrong soil for its species or going hungry will often refuse to flower. The timing of pruning is the other common culprit. A prune at the wrong time of year can cut off the buds that would have opened.
How treatable is it? Often it can be corrected, because the causes are light, drainage, feeding and the timing of pruning. If the position does not suit the species, the plant will keep struggling there.
What to do
| Step | What to do |
|---|---|
| 1 | Check how much sun the plant gets through the day. A sun loving plant in shade will not thrive however well it is watered, so if the spot is too shady, replace the plant with one that suits the light. |
| 2 | Check whether water drains away or sits around the roots. If it sits, the plant is in the wrong position for its species. In heavy clay, a layer of coarse mulch helps over time and any replacement should go in slightly raised. See natives for clay soil. |
| 3 | Compare the plant with the conditions its species prefers. Check where the species grows naturally and whether your position delivers it. If they do not, the position is the likely cause and the plant will keep struggling there. |
| 4 | Feed only with a product made for natives, because phosphorus is not suited to members of the protea family such as banksias, grevilleas and hakeas. |
| 5 | Prune at the time that suits your species, which is often straight after flowering, and avoid cutting off developing buds. Regular pruning encourages more flowers even on a plant covered in buds. Use clean, sharp secateurs and see our guide to pruning natives. |
| 6 | If the plant is young it may still be establishing, which is covered in why native plants can fail in the first year. |
Before you reach for a fix
Ordinary fertilisers can add to the problem, as our guide to why all-purpose fertiliser harms natives explains. Check the soil, the water and the position first, then change one thing at a time.
7. Why does water run straight off my potted native and the plant still wilts?
This is usually water-repellent, or hydrophobic, potting mix. When a mix dries out completely, a waxy residue builds up on the particles and repels water. The water beads on the surface or runs straight through the drainage holes while the mix stays dry. Dried-out potting mixes are especially prone to it, as are sandy soils.
To test it, water the pot and watch. If the water soaks in, the mix is fine. If it pools on top or runs straight out, the mix has turned hydrophobic.
How treatable is it? It can usually be corrected, because soaking the pot from below rehydrates the mix. It can return if the mix dries out completely again.
What to do
| Step | What to do |
|---|---|
| 1 | Stand the pot in a tub of water deep enough to cover it and leave it for 10 to 20 minutes so the mix rehydrates from below. |
| 2 | For a short-term fix, use a wetting agent and check that the product suits your plants. |
| 3 | If the problem keeps coming back, repot into fresh mix. |
| 4 | Keep a layer of mulch on the surface to slow drying or use a mulch mat. |
| 5 | Consider a terracotta olla to keep moisture steady. Our guide to natives for pots covers choosing plants and mixes for containers. |
8. Why are the leaves on my gum tree red, blotchy or chewed, and why is the bark peeling?
Several insects cause leaf symptoms and each leaves its own pattern.
- Yellowing or reddening leaves. Lerp psyllids can turn leaves yellow or red and the damage can end in dead leaves and leaf fall.
- Ragged edges. Christmas beetles feed on mature leaves and leave a torn, jagged pattern along the edges.
- Blisters on older, lower leaves. Leaf blister sawfly larvae tunnel just under the leaf surface and heavy attacks can bring on early leaf fall.
- Red-brown bronzing. Winter bronzing bugs suck sap from the leaves and badly affected leaves drop early.
How treatable is it? Not every insect needs action. Free-living psyllids and leafrollers rarely do serious harm to a tree. Lerp species that seldom discolour leaves are a lower concern, although very high numbers leave honeydew and sooty mould. Repeated attacks are the main worry. Young trees up to about three years old are most at risk from Christmas beetles, and small or stressed trees are the ones most affected by scale.
What to do about leaf damage
| Step | What to do |
|---|---|
| 1 | Identify the damage before acting, because the right response depends on the insect. |
| 2 | Reduce stress. Water deeply in dry spells and avoid disturbing the roots. |
| 3 | For scale and the ants and sooty mould that come with it, see our guide to common issues with native plants. This will need a longer-term and routine approach. |
| 4 | If the tree is large or the damage spreads year after year, seek the advice of an arborist. |
Peeling bark
Peeling bark on a eucalypt is usually normal. Many gums shed their bark every year, typically in summer, and the old bark curls away in strips to leave fresh bark underneath. Smooth-barked gums such as brittle gums and scribbly gums shed all or some of their bark. Stringybarks, boxes, peppermints and ironbarks keep a rough outer layer instead.
How treatable is it? Nothing needs treating on a smooth-barked gum, because summer shedding is normal.
What to do about peeling bark
| Step | What to do |
|---|---|
| 1 | Check which type of gum you have. |
| 2 | On a smooth-barked gum, summer shedding is normal and needs no action. |
| 3 | If a stringybark, box, peppermint or ironbark is peeling, or the tree is also dying back or dropping its leaves, ask an arborist to assess it on site. |
9. Why are the leaves on my fern brown and dry?
Three things commonly damage fern fronds: a long spell of dry heat and wind, frost and too much direct sun. A fern that has been watered regularly through winter copes with frost better, and some ferns tolerate sun but not for long stretches.
How treatable is it? A damaged frond will not recover, so treatment means removing damaged fronds and preventing further damage.
What to do
| Step | What to do |
|---|---|
| 1 | Remove damaged fronds with clean, sharp snips. A damaged frond will not recover. |
| 2 | Where frosts are likely, keep watering regularly through winter. Our guide to protecting natives from frost has more detail. |
| 3 | If the fern has had long spells of direct sun, reduce its exposure by moving a potted fern or shading the plant from the strongest sun. |
10. Why does my grevillea look yellow and unhealthy?
Grevilleas belong to the protea family, which is sensitive to iron, phosphorus and soil pH. Yellow leaves usually point to one of these four causes.
- Iron shortage. New leaves turn yellow while the veins stay green. It is most common in alkaline soil.
- Too much phosphorus. It can cause widespread yellowing and damage the roots, often after a feed that was not made for natives.
- Alkaline soil. It can stop a plant absorbing nutrients even when they are present.
- Waterlogged roots. They give pale, weak foliage.
How treatable is it? An iron shortage can be corrected with chelated iron, which may need repeating until the symptoms clear. Waterlogged roots depend on fixing the drainage.
What to do
| Step | What to do |
|---|---|
| 1 | If the new leaves are yellow with green veins, apply chelated iron. It supplies iron the plant can take up even in alkaline soil and may need repeating every few weeks until the symptoms clear. |
| 2 | Do not add lime or dolomite, because both raise the pH. |
| 3 | If you feed, choose a low-phosphorus fertiliser made for natives and avoid products with more than 3% phosphorus. See why all-purpose fertiliser harms natives. |
| 4 | If water sits around the roots, water deeply but less often and lay coarse mulch. |
Start from the bottom up in most cases
Most native plant problems come back to the same three things: roots that are too wet or too dry, a position that does not suit the plant and pruning or feeding at the wrong time. Working through those before reaching for a product usually solves more problems than any spray.
keep reading
A Guide to Australian Native Gardening
How to plan, plant and care for a thriving native garden, whatever your experience level.
Read the guide →
