Unlock the secrets to healthy, happy citruses with tips for diagnosing and solving common garden problems.
Jump to Our Handy Citrus Problem-Solving Checklist
For all the lemons life gives us, there is nothing more joyful than growing a lemon tree in the garden. Yet, citrus remains one of the most talked about and problematic plants for Tasmanian gardeners. Wind, frost, nutrient deficiencies and possums all work against us to grow the perfect tree. Citruses are temperamental beauties that are quick to throw tantrums and show signs of distress. Understanding the causes of common problems is key to helping your tree thrive.
Feeding
Citruses are gross feeders. Regular feeding is essential for strong growth and abundant fruit. They benefit from a balanced fertiliser specially formulated for citrus trees applied in winter, spring and late summer, when they are actively growing and flowering. Avoid overfeeding, however, as too much nitrogen can lead to vigorous leafy growth at the expense of flowers and fruit. Slow-release granular feeds, pelletised fertilisers or liquid feeds are ideal, giving trees a steady supply of nutrients over time.
Pot citruses benefit from quick-acting feeds at more frequent intervals, while in-ground citruses benefit from a good, strong dose of rich, organic fertiliser, top dressed with slow-release fertiliser at least three times a year.
Watering
Both overwatering and underwatering can cause problems. Citrus prefer deep, infrequent watering that encourages strong root systems. Shallow, frequent watering can lead to weak roots and increase susceptibility to pests and disease. Mulching around the base helps retain soil moisture and keeps roots cool, particularly during Tasmanian dry spells.
Avoid using trays for potted citruses and allow pots to drain freely by propping them up with pot feet.
Soil
Citruses thrive in well-drained soils rich in organic matter. Heavy clay or poorly drained soils can cause root rot and produce yellow leaves. If drainage is an issue, consider planting on a slight mound or in raised beds. Adding compost or well-rotted manure improves soil structure and fertility, giving citrus the environment they need to flourish.
Nutrient Deficiencies
While nitrogen is important, many citrus problems arise from deficiencies in trace elements such as magnesium, iron, manganese, and zinc. Signs can include:
- Iron deficiency: Yellowing leaves with green veins (chlorosis), particularly in young growth.
- Magnesium deficiency: Magnesium deficiency leaves a distinct yellow pattern in the older leaves. The yellowing begins near the edge, creating a triangle of green at the base of the leaf.
- Zinc deficiency: Small, distorted leaves or shortened internodes. Zinc deficiency leaves a bright yellow mottle.
A balanced trace element mix, applied according to package instructions, can correct deficiencies. Foliar sprays can provide rapid relief, while soil applications build longer-term health.
Nitrogen deficiency
Magnesium deficiency
Wind stress – upward curled leaves/ ‘boating’
Possible insect infestation – check underside of leaves for insect activity
Zinc deficiency
Potassium deficiency
Scale insect on underside of leaf
Sooty mould as a result of scale or aphid infestation
Recommended products for trace elements
Pests
Citruses attract a range of pests, including aphids, scale, leaf miners, caterpillars, and even katydids. Signs of infestation include distorted leaves, sticky residue, or small holes in fruit. Early detection is key: check leaves regularly and encourage beneficial insects, such as ladybirds and lacewings. Horticultural oils or insecticidal soaps are effective, low-impact treatments for most common pests. Check out our latest article on combating pests like aphids and scale.
Protection
Tasmanian weather can pose tricky challenges for even the most seasoned gardener. Citruses particularly detest wind, so consider protecting plants with a frost cloth or temporary windbreak. Remember to give your trees a deep drink after a windy day. If there is one being that loves your citrus tree more than you, it’s the friendly neighbourhood possum. Exclusion is the only truly effective protection from possums, so consider keeping your tree small so that you can easily protect your tree when required. Seasonal pruning not only shapes the tree but also improves airflow and reduces pest and diseases.
Come in to Explore Our Diverse Range of Citrus Trees
Handy Citrus Problem-Solving Checklist
|
Signs & Possible Causes |
What to Do |
|
Yellow leaves with green veins |
Iron deficiency → Apply iron chelate as foliar spray or soil drench |
|
Yellow edges of older leaves |
Magnesium deficiency → Use magnesium-containing fertiliser (Epsom salts or trace-element mix) |
|
Yellow splotches between veins, and smaller distorted new growth |
Zinc deficiency → Foliar spray or soil-applied zinc |
|
Leaf curling downwards, sticky residue, or sooty mould |
Aphids or scale → Encourage ladybirds, use horticultural oil or insecticidal soap |
|
Leaf curling upwards |
Wind stress → Install temporary windbreaks and water deeply after windy days to reduce stress |
|
Holes in leaves |
Caterpillars, katydids or leaf miners → Inspect regularly, hand-pick or treat with low-impact insecticide |
|
Damaged fruit |
Caterpillars, birds, possums or rats → Inspect regularly, hand-pick, create exclusion barriers |
|
Weak growth or few flowers/fruit |
Overwatering or excess nitrogen → Adjust watering, switch to balanced or low-nitrogen fertiliser |
|
Frost-damaged leaves or branches |
Frost exposure → Protect with frost cloth or temporary windbreaks, move to a protected North- or West-facing area |
|
Sparse canopy or poor airflow |
Overcrowded branches → Prune to shape tree and improve ventilation |
