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Yellow Leaves - Causes and Cures

Yellowing leaves on indoor plants and what to do
Yellowing leaf on a Chinese Money Plant

There can be several different reasons for yellowing leaves. Sometimes the cause is obvious, as in the case of this Chinese Money plant, which is simply shedding an old leaf and putting energy into new growth.

Other times the problem is more of a mystery! In these cases, you'll need to try changing one thing at a time until you see an improvement with your plant.

Let's look at some of the common causes for yellowing leaves and how to fix them.


1 Watering Issues

Often the most common cause for leaves turning yellow is due to either overwatering or underwatering.

The first thing to do in this situation is check the soil. Is it dry? Is it soaked?

Overwatering Causes:

If you water too regularly, the soil doesn't have a chance to dry out and houseplant roots need oxygen, so if the soil stays wet for too long the roots can rot. That's why I always recommend sticking your finger right into the soil to check how moist it is before you water.

Believe it or not when roots rot in wet soil due to over-watering, it's actually a result of watering too frequently rather than giving too much.

Overwatering Cures:

If you have overwatered, check the roots to see if they're brown and mushy. Remove any dead roots. You could use some paper towels under the pot to absorb excess moisture or try repotting with dry compost.


Underwatering Causes:

Conversely, giving too little water can also cause yellowing leaves. If a plants soil has completely dried out, they drop leaves to conserve water. Before they drop, the leaves will typically turn yellow, sometimes at the tips, and sometimes with brown spots. An early warning sign is leaves drooping or curling up (as Calathea's do).


Underwatering Cures:

Rehydrate the soil. Give your plant a good soak or stand it in water for 10-20 minutes, depending on the size of the pot. Feel the weight of the pot when it's dry and once it has been watered so you'll know what each feels like for future. Set a regular reminder to check your tropical plants soil weekly in spring and summer and fortnightly in winter. You could stick your finger into the soil, use a moisture meter or feel the weight of the pot.


2 Lack of Nutrients


Causes:

The second common cause, more likely in spring and summer - is a lack of nutrients.

Over time the nutrients in the soil get used up. Yellowed leaves can indicate nitrogen deficiencies.

Cures:

Use a fertiliser which is high in nitrogen to feed your hungry plants. Depending on the type of plant you should fertilise every 2 - 4 weeks during the growing season, spring and summer. I have a range of fertilisers in the shop.


3 Lack of Light

Causes:

Plants that receive too little light will often start to yellow on the lower leaves, usually on the side that's turned away from the light source. This can happen if the leaves near the window are getting all the light and blocking those at the back. Another cause is that you may have your plant in too dark a location. Also in winter, when light levels are lower, plants can suffer from yellowing leaves.

Cures:

A great way to remedy this is to rotate the pot a quarter turn once a week, so all sides have access to natural light.

You could also try moving your plant to a brighter location and see how it does. If window light is tough to come by in your home—especially in winter—you may want to consider buying grow lights.


4 Cold draughts

Causes:

If your plant is near a draughty window, particularly in winter or near an air-conditioning unit this may result in yellowing leaves which drop. This is different from short periods of exposure to intense cold, which will cause outright browning on the foliage or transparent spots to appear between veins.

Cures:

Easy solution, move your plant to a less draughty place and keep an eye on it to see if the yellow leaves spread any further.


5 Pests

Causes:

Sometimes your plants can be attacked by pests. These can come in on other plants or from the garden. Plant insects, such as spidermites or aphids, may be feeding on the sap from your plants and turning them yellow, leaving discoloured patches. Check under the leaves for any signs of fine webbing, which can indicate spidermites or look in any little crevices between stems for other pests, like mealybugs.

Houseplant pest control spray
SB Plant Invigorator spray indoor plant pest control

Cures:

Use a pesticide spray. I have a couple of good options in stock, which are safe to use around pets, children and edible plants.

SB Plant Invigorator and Bug Killer is an environmentally friendly pesticide and growth stimulant. It controls a wide range of pests including: Mealybugs, Scale, Spider Mites, Aphids and White Fly. It also controls mildew.

It uses a physical mode of action so pests won't become resistant and contains a foliar feed for strong growth.

Also SMC Spidermite Control spray is a premium quality leaf wash and insect eliminator, which is safe, natural and highly effective in controlling spidermites and common plant pests.


Finally...

It's very tempting to snip off unsightly yellowing leaves. I have to admit I've been totally guilty of this in the past but there is a good reason not to break out the snips before they're ready to drop.

Your plant is taking water, sugars and other nutrients out of the leaf to help support the health of the rest of the plant.

The only exception for removing yellowing leaves, which is unusual, is if the leaves are also brown and mushy, it could be an infection. Then remove them so the infection doesn't spread and isolate your plant while you try to treat it with a fungicide.


Thanks for reading.

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