Leaves turning brown is usually an indication of problems with watering or the root system but can also be as simple as sunburn from too much exposure to the sun.
Plants lose water naturally through their tissues. And leaf tips and edges will turn brown when the lost water for some reason or another cannot be replaced.
And from my experience this problem will pop up every now and then and effect all kinds of plants including but not limited to
- Herbs like basil where leaves go yellow or brown at the tips and edges
- Avocado plants with browning and even crispy leaves
- Houseplants where leaves get brown and fall off
- Vegetables like squash where pests may cause leaves to brown and wilt prematurely
- Seedling leaves turning yellow for no apparent reason
- Fruit plants like cherry tomato, beefsteak tomato and chilli pepper plants where leaves shrivel and go brown
Because at the end of the day plants are living things with needs and wants. And if you fail to serve those needs your plants will suffer. Leaves turning brown is simply your plant telling you that it needs some tender love and care.
Before looking at fixes, let’s focus on understanding why leaves turn brown on your plants.
5 reasons leaves turn brown
1. Overwatering and underwatering will cause leaves to brown
As with most things related to gardening there is a cause and effect that sometimes make it hard to identify the root cause (no pun intended) of the problem.
A good example is under and over watering. Here plants will often respond with the wilting, yellowing and browning of the leaves whether we water too much or not enough.
And looking at the home gardeners that I come in contact with many plants are overwatered for all the wrong reasons.
It goes something like this.
- Leaves are browning at the tips or edges
- The soil doesn’t look wet or dry
- Let’s water the plant to be on the safe side
In cases where the plant is already overwatered this watering behaviour will cause damage to the root system and may even kill your plant.
2. Leaves turning brown due to soil problems
A good quality soil that drains well is key for the survival of most plants. And as with all things gardening you are looking for a balance and a soil that
– drains well, but not too well
Your soil must hold moisture but cannot be wet or soaking. Root systems sitting in constant wet will rot and die and effectively kill your plant. Constant wet means no oxygen and no root serum will survive without oxygen.
On the other hand, a sandy soil will let water run right through without retaining any moisture. Here your roots will have plenty of oxygen but no water or moisture.
You want the balance of a soil that retains moisture while allowing excess water to run off. As the excess water runs off, the soil gets aerated and you have your balance.
– has structure but is not too compact
A good and healthy soil has structure where humus and organic matter creates support for root systems and plants to grow.
But if the soil is too compact or hard it will stunt the growth and development of your plants. The same is true for using a pot, grow bag or container that is too small for the plant’s root system.
Again, you are looking for a balance.
– is nutrient rich but not over fertilised
An over fertilised soil will hurt your plants and one of the first indications can be the yellowing or browning of leaves.
Salt buildup in your soil can also cause leaves to go brown. Bottom watering plants have many advantages over traditional top watering with a watering can.
But when you bottom water plants it is important to also, every now and then, thoroughly water the plant from the top. This thorough top watering where you let the excess water run off a couple of times can help remove harmful build-ups of salt in your soil.
3. Damaged root systems causing leaves turning brown
Root systems can get damaged for any number of reasons including over and underwatering, lack of oxygen, compact soil or just a general poor quality of soil.
And roots that are too constricted or damaged will be unable to do their job and reach out to collect or absorb water.
From my experience it is often not worth the effort to try to save a plant if the root system shows clear signs of damage like root rot. The roots will have lost their white colour and feel slimy to the touch. There can also often be an unpleasant odour.
4. Browning leaves due to the end of the plants life cycle
Sometimes we have to accept that a plant has come to the end of its natural life span.
And most vegetables and plants naturally turn brown and wither in the fall and winter when their life cycle is over.
This is especially true for annuals but also perennials that often are grown as annuals in cooler zones.
5. Pests and diseases can cause leaves to brown
Leaves can also turn brown from pests and diseases. With pests the problem often starts as brown spots where the leaves are penetrated and sucked dry.
Scale, mealy bugs, spider mites, leaf miners and aphids are some examples of pests that can cause leaves to turn brown.
We treat all infestations with a Neem oil and water mixture that is sprayed on the leaves early morning or evening. Never treat your plants when they are exposed to direct sunlight.
How to fix milder cases of leaves turning brown
Before you do anything you need to assess the level of browning that you are dealing with.
If less than 10% of the leaf area is affected, correct your ways and leave the plant to heal itself back to health.
Examples could be sunburned plants placed too close to a sunny window or cases of under and overwatering.
There is no reason to inflict potential stress on your plant by cutting, pruning or transplanting if you have identified and can remove the cause of the browning of the leaves.
3 steps to fix more severe cases of leaves turning brown
But often, you will find that the problem goes beyond a few browning tips or edges. And when this is the case you will most likely need to repot and possibly pot up the plant with fresh soil.
But first, you should try to understand why the leaves turned brown in the first place.
1. Inspect soil and level of moisture
Use your fingers to dig down about 3 cm / 1 inch to get a feel for the level of moisture in the soil.
Was it as expected?
If not, you have your first clue that your watering habits are a part of the problem.
2. Remove plant from pot and inspect root system
Next, gently remove the plant from the pot and look at the root system.
Are the roots white and healthy looking?
Is the plant pot bound or is there more room for roots to grow?
Are some areas of the root system dry or maybe even wet?
Remember, you are looking for a moist, white and odour free root system.
This visual inspection will help you decide on the size pot you will need for your plant going forward as well as help you assess the overall health of the root system.
3. Examine quantity and quality of soil
Look at the soil in the pot and try to get a feel for its structure and quality.
Does it look like the soil drains well?
Does it seem like the soil holds an even level of moisture?
Is there enough soil for the root system to grow and develop?
Use the answers to the questions above to help decide on the type soil and size of pot you will need.
Summary: Why are my leaves turning brown
Leaves turn brown from underwatering, overwatering, sunburn, overfertilization, poor soil quality and many other factors.
And it is not always obvious why your leaves turn brown.
If less than 10% of the leaves are turning brown you should look for obvious reasons such as sunburn and over or under watering before you disturb the plant with an unnecessary pot up.
If the problem is more severe or you feel that it is getting worse, you should follow the process below to help fix your plant’s problem with brown leaves.
- Examine the plant and its root system
- Look for clues to why your plant’s leaves are turning brown
- Learn from inspection and repot plant in new environment
Useful resources:
https://extension.usu.edu/news_sections/gardening/ask-an-expert-why-are-my-leaves-turning-brown
