Lemon tree leaves can develop brown leaves if they are not getting enough water or if their leaves are being attacked by snails, slugs, aphids, caterpillars or bronze orange bugs. Lemon tree leaves will also turn brown if they are experiencing an ongoing lack of nutrients including nitrogen and iron.
This article will explore why lemon tree leaves turn brown and how you can address each problem. Leaves can repair quickly if the issue is identified and fixed fast. Keep reading for the top causes and solutions to brown leaves on lemon trees.
1. Lack of water
The top cause of brown leaves on lemon trees is a lack of water. Lemon trees are thirsty plants and if they are allowed to dry out they can quickly develop brown and yellow leaf tips. This will spread to the rest of the leaf quickly, then down the stems.
Soil that is too sandy can dry out quickly so it is essential to improve the soil before planning lemon trees. I like to dig through aged cow manure and compost to add extra organic matter to hold water for longer. Choose a good quality potting soil if you are growing lemon trees in pots so that it holds water well.
Test the soil with your finger 2 inches below the surface and if it is dry, deep water it with your hose. Completely soak the root zone of the lemon tree. You can also mix up liquid seaweed in a watering can and give it to your lemon tree.
This will help the plant to develop a strong root system and recover faster. Surround the tree with 2-3 inches of sugar cane, straw or bark mulch to keep the water in for longer.
2. Caterpillars, slugs and snails
Chewing pests such as caterpillars, slugs and snails can all cause brown leaves on your lemon tree. They will eat holes in your leaves or chew from the edge of the leaf inwards.
This usually causes the leaf to turn brown around the edge or hole that has been eaten.
The easiest way to deal with caterpillars is to wear gloves or use a small spade and flick them off into a bucket of soapy water. Wear protective glasses if you are unsure of the species of caterpillar as some can excrete substances that can irritate eyes.
Slugs and snails usually come out throughout the night and will return to hide in the organic matter on top of the soil. If you head out in the early morning you can sometimes catch them on your leaves chewing.
Prevent snail and slug attack by setting up a beer trap. Fill a shallow tray with beer and place it near your lemon tree. Surround the lemon tree with old coffee grounds or crushed egg shells. Snails and slugs hate crawling over the sharp egg shells and really hate coffee.
3. Aphids, thrips and spidermite
Sap sucking insects such as aphids, thrips or spidermite can attack your lemon tree, most commonly in spring and fall. They will attach themselves to the veins or stems of the plant, sucking the plants sap and eventually turning the leaves brown.
Small numbers of aphids can be dealt with by natural predators such as ladybugs which can eat up to 100 aphids a day. Aphids breed quickly so if you see their numbers getting out of hand, spray them with a dilute mix of neem oil. This is an oil extract from the neem tree that will get rid of these insects without harming others.
Spidermite and thrips can also be treated with neem oil. Make sure you spray the leaves on both sides and cover the leaf stems where the insects are sitting. You may need to repeat the process again in a few days to get rid of all of the bugs.
4. Bronze orange bugs
Bronze orange bugs are a common pest that will attack your plants in spring. These large beetles will attack the new growth on your lemon tree, quickly causing it to wilt and turn brown. These bugs love warm, wet weather and can rapidly breed in the right conditions.
This year my lemon tree was covered in bronze orange bugs. There numbers were huge so they had to be treated with 3 doses of neem oil. After 3 applications the bronze orange bugs were completely gone.
I would keep a bottle of neem oil mixed up and sprayed it all over the bugs and new growth every 4-5 days. This will be enough to get rid of the bugs without harming pets, other insects or yourself.
5. Lack of nitrogen
Lemon trees that lack nitrogen can develop brown leaves. Nitrogen is needed for the chlorophyll to develop in the leaves giving them their green color. Without this, the leaves will look yellow and then eventually brown.
If your lemon tree leaves have turned brown due to a lack of nitrogen it can be easily fixed. Simply add a dose of nitrogen based liquid fertilizer and then follow up with a handful of pelleted chicken manure. Water it all in well and repeat the process after a month.
You can also top dress citrus trees in spring with a mix of aged manure and compost. Mix though aged chicken manure, cow manure and compost in a 1:1:1 ratio and gently rake 1-2 inches of this mix on top of the root zone and water it in well.
Cover the mix with 2 inches of mulch and your plant will gently get an extra dose of nitrogen over spring and summer.
I like to feed my plants with a dose of citrus food at the start of every season to make sure they have the nitrogen they need. These mixes also contain a range of trace elements that will replace any lost during fruiting.
6. Lack of iron
A lack of iron can cause lemon trees to develop yellowing leaves with deep green veins which will eventually turn brown. If this problem is left untreated the growth of the lemon tree will slow and fruit production will reduce.
If your tree is lacking nitrogen give it a dose of liquid iron chelates. This can be bought as a powder, mixed up and watered around the root zone of your plant. This should fix the problem within a month.
Feed your lemon tree regularly with a citrus fertilizer that contains iron. This will help to prevent this problem from occurring.
7. Brown rot
Lemon trees can develop brown rot which is a fungus that comes from the soil. When there is heavy rain or if you are watering straight onto the soil this bacteria can splash up and get on the leaves and fruit. The plant will develop brown spots on the leaves and the fruit at the same time.
You can treat this problem with a copper fungicide. It is more likely to happen in fall when the weather has cooled but there is still rain around. You can also spray this on the leaves to prevent this problem when the weather cools.
To prevent brown rot it is important to surround your tree with 2-3 inches of bark or straw mulch. This will help to stop soil from splashing up onto the leaves, stems and fruit and spreading the fungus.
Remove any branches that are close to the ground so that it is less likely that the soil will splash onto the leaves.
Lemon tree leaves turning brown | Summary
Lemon trees are hardy plants but their leaves can turn brown due to a lack of water, nutrients or bug attack. Feed lemon trees with a well balanced fertilizer like a citrus fertilizer topped up with pelleted chicken manure each season. Water it well over the warmer months and surround it with 2-3 inches of bark or straw mulch. This will keep the water in and help to prevent brown leaves.