Rhubarb leaves turning brown can be a cause for concern for gardeners. There are several reasons why this might happen, and fortunately, there are also several solutions. In this blog post, we will explore the causes of rhubarb leaves turning brown, as well as some ways to correct the problem. Keep reading to learn more!
Why Are My Rhubarb Leaves Turning Brown?
Brown leaves on rhubarb plants are typically caused by fungal diseases, insects, overwatering, leaf burn, and nutritional deficiencies. The specific browning will be determined by the reason for the discoloration. Brown, crisp patches may appear on leaves if they are exposed to too much sun, whereas fungal infections cause brown spots.
To gain a better understanding of why your rhubarb leaves are turning brown, it is important to take a closer look at the plant. Check the undersides of the leaves for insects or egg sacs. Fungal diseases often start as small brown spots that eventually spread and cover the entire leaf.
Once you know what is causing the brown leaves, you can take steps to correct the problem. I will now go further into detail about each of the potential causes, as well as their solutions.
1. Browning Rhubarb Leaves from Fungal Infection
If brown spots are appearing on your rhubarb leaves, it is likely due to a fungal infection. The most common type of fungus that affects rhubarb plants is Anthracnose. This disease starts out as small, dark brown spots on the leaves. The spots eventually grow and spread until they cover the entire leaf, at which point the leaf will turn brown and die.
To prevent Anthracnose from infecting your rhubarb plants, it is important to practice good plant hygiene. This means removing any dead leaves or debris from around the plant, as well as pruning any affected leaves. You should also water the plants at the base of the stem, rather than from above, to avoid getting water on the leaves.
If your plant is already infected with Anthracnose, you can treat it with a fungicide. Be sure to follow the instructions on the product label carefully. I recommend using neem oil (Amazon link), which is a natural, organic fungicide.
Simply apply the neem oil to the affected leaves, being sure to cover both sides. You will need to reapply the fungicide every two weeks or so until the infection is gone.
2. Browning Rhubarb Leaves from Overwatering
Overwatering is another common cause of brown leaves on rhubarb plants. When the roots of the plant are constantly wet, they become oxygen-deprived and begin to die. This causes the leaves to turn brown and wilt.
To prevent overwatering, it is important to water your plants only when the soil is dry. You can check the moisture level of the soil by sticking your finger into it. If the soil is dry up to your second knuckle, it is time to water the plant.
If you think your plant is already suffering from overwatering, there are a few things you can do to save it. First, stop watering the plant until the soil is dry. Next, increase the drainage of the pot by adding some holes to the bottom. Finally, you can try replanting the rhubarb in a different pot with fresh, well-draining soil.
3. Browning Rhubarb Leaves from Pests
Insects and other pests are another common cause of brown leaves on rhubarb plants. The most common pests that affect rhubarb are aphids, caterpillars, and Japanese beetles. These pests feed on the leaves of the plant, causing them to turn brown and die.
To prevent pests from infesting your rhubarb plants, it is important to practice good plant hygiene. This means removing any dead leaves or debris from around the plant, as well as pruning any affected leaves.
The best way to get rid of these pests for sure is with neem oil (Amazon link), which works as both a pesticide and a fungicide. Simply apply the neem oil to the affected leaves, being sure to cover both sides.
Moving forward, it is important to take steps to prevent brown leaves on your rhubarb plants. The best way to do this is to practice good plant hygiene, including removing dead leaves and debris and pruning any affected leaves.
4. Browning Rhubarb Leaves from Leaf Burn
Leaf burn is another common cause of brown leaves on rhubarb plants. This usually occurs when the plant is exposed to too much direct sunlight. The leaves will turn brown and dry out, eventually dying.
To prevent leaf burn, it is important to make sure your rhubarb plant is getting enough water. Water the plant at the base of the stem, rather than from above, to avoid getting water on the leaves.
You should also make sure the plant is getting enough shade. If it is exposed to too much direct sunlight, you can try moving it to a different location or providing some additional shading.
5. Browning Rhubarb Leaves from Nutrient Deficiencies
Nutrient deficiencies are another common cause of brown leaves on rhubarb plants. The most common nutrient deficiency that affects rhubarb is nitrogen. This can be caused by a lack of nutrients in the soil or by too much water.
To prevent nutrient deficiencies, it is important to fertilize your rhubarb plants regularly. I recommend using an all-purpose fertilizer (Amazon link) that is high in nitrogen. This will help to ensure that the plants are getting all the nutrients they need.
Will Brown Rhubarb Leaves Turn Green Again?
No, it is extremely unlikely that brown rhubarb leaves will turn green again. Once the leaves have turned brown, they are usually dead and will eventually fall off the plant. If you notice that your plant has a lot of brown leaves, it is important to take steps to prevent further damage.
The good news is that your rhubarb will continue to produce new leaves, even if some of the old ones are brown. As long as you take steps to prevent further damage, your plant will eventually recover.
Should I Prune Brown Rhubarb Leaves?
It is usually not necessary to prune brown rhubarb leaves, as they will eventually fall off the plant on their own. However, if you notice that your plant has a lot of brown leaves, you can help it to recover by pruning some of the affected leaves.
To do this, simply cut off any brown leaves at the base of the stem. Be sure to dispose of the leaves properly, as they can contain harmful toxins.
As we have seen, there are a few different reasons why rhubarb leaves might turn brown. The most common causes are nutrient deficiencies, overwatering, fungal problems, leaf burn, and pests. However, as long as you take steps to prevent further damage, your plant will eventually recover.
If you have any questions or comments, please feel free to leave them below. I would love to hear from you! Thanks for reading!
Tim is an avid gardener from the UK. He was the founder of PlantCarer.com from 2021 to Sep 2023. He sold PlantCarer.com to Aaron. He has since started his own business called Seed To Supper, which provides new gardeners all the materials you need in a box (pots, seeds, compost and instructions) to grow your own delicious and nutritious vegetables and herbs from start to finish – no garden required.