Why Are My Plant Leaves Turning Yellow? Causes, Fixes & Prevention Tips

Yellowing leaves are one of the most common issues faced by home gardeners. Whether you’re caring for an indoor peace lily or a flowering gardenia, discoloured foliage usually signals a stressor in your plant’s environment. Understanding these signs early can help you restore health before irreversible damage sets in.

1. Most Common Causes of Yellow Leaves

There are several reasons a plant’s leaves may begin to yellow, each pointing to a different type of imbalance. The most typical causes include:

Overwatering – Roots sitting in waterlogged soil lose oxygen, leading to yellowing, mushy leaves. Check if your pot drains well.
Underwatering – If leaves turn crispy yellow, especially on the edges, the plant is likely dehydrated. Water deeply and consistently.
Low light conditions – Insufficient sunlight affects chlorophyll production, causing pale yellow or faded green leaves. Adjust placement.
Nutrient deficiency – Lack of nitrogen or magnesium often causes yellowing, especially in older leaves. A balanced fertiliser can resolve this.
Temperature stress – Sudden changes or drafts can trigger leaf yellowing. Keep plants within a stable 18–26°C range.

Early detection is essential. By observing leaf patterns—such as whether yellowing begins at the tip, edge, or whole leaf—you can often pinpoint the issue.

2. Yellow Leaves on Common Australian Plants

While yellowing symptoms are common, the specific cause may vary between plant species. Here’s a breakdown of frequent culprits by popular plant types:

Gardenia

Yellow leaves on gardenias are often due to high soil pH (alkaline conditions) or iron deficiency. These plants thrive in slightly acidic soils and benefit from fertilisers designed for acid-loving species. Always check that your gardenia is receiving consistent moisture and is not exposed to harsh afternoon sun.

Orchid

Orchids can show yellowing due to overwatering, especially if they’re in tightly packed bark or moss. Ensure the potting medium dries slightly between waterings and avoid direct sunlight. If your orchid is between blooming cycles, light yellowing may be normal.

Peace Lily & Monstera

For these popular indoor plants, irregular watering and nutrient depletion are common problems. Yellow leaves in a peace lily typically begin at the outer edge, indicating water stress or low nitrogen. Use a balanced liquid fertiliser every 2–4 weeks during the active growing season to maintain leaf colour and vigour.

Regardless of plant type, it’s important to use clean tools when removing yellow leaves to prevent fungal spread or bacteria.

3. Frequently Asked Questions About Yellowing Leaves

Should I cut off yellow leaves?

Yes. Trimming yellow or damaged leaves helps redirect energy to healthy parts of the plant. Always use sterilised scissors and cut close to the base without damaging the main stem.

Can too much fertiliser cause yellow leaves?

Excess fertiliser can lead to salt build-up in soil, which damages root systems and causes yellowing. Use a well-balanced, water-soluble fertiliser like CompleteGrow’s 20-20-20 at recommended dilution rates to avoid this issue.

How often should I fertilise to prevent yellowing?

Indoor plants typically benefit from feeding every 2–4 weeks in spring and summer. Outdoor plants may require less frequent feeding depending on weather and soil condition. Always monitor your plant’s response and adjust accordingly.

Tip: Yellowing is often the first visual sign of nutrient deficiency. Using a complete fertiliser with trace elements—like CompleteGrow’s NPK 20-20-20—can restore colour and vitality within 7–14 days.