Overwatering is the most common cause of yellowing agave leaves. However, you should assess the situation further because there are other things to look out for, such as root rot diseases, pest infestation, and nutrient deficiency. If your agave has root rot, repot it into a new pot. Water only when the topsoil is dry.
If you are experiencing this problem, I will walk you through all of the possible causes and solutions.
Causes of Agave Leaves Turning Yellow
Simply by looking at your plant, you can tell if your Agave is suffering from this condition. However, keep in mind that there are other Agave species with a yellowish stripe or a yellow-green color.
To properly determine whether your plant requires treatment, you must first identify the type of Agave that you own. It’s also worth noting that Agave thrives in desert or sandy areas because it can withstand more sunlight than other garden plants.
They can usually survive with only a small amount of water. Now, let’s go over some of the causes in more detail and get a sense of how you’re going to address them.
Amount of Water
Watering is the most basic thing that you need to know in taking care of indoor plants.
You need to understand that not all types of plants require the same amount of water.
That’s why it’s important to know the natural environment where your plant usually thrives.
Overwatering your Agave might lead to not just turning its leaves yellow but other serious problems as well.
You can also tell that it’s overwatered if the leaves look mushy and the tips are turning brown.
On the other hand, underwatering it especially during mid-summer might also result in its leaves becoming yellow accompanied by wrinkling and wilting from its ends.
What to Do:
- The first step is to identify its water needs for the time being.
- If you think your plant is overwatered, then place it in a brighter area which will help the soil to dry out faster. Let the soil dry out first before watering it again. Typically around 10-12 days of watering intervals.
- If you think your plant is under-watered, then consider watering it thoroughly until there are signs of excess water dripping from the drainage holes of your pot. Then let it dry before watering again.
- Make it a habit to remove dripped waters on the pot saucer to avoid the delay in draining the soil.
Leaves that are turning yellow is a big sign that it lacks nutrients. Commonly, it’s the lack of magnesium that brings that kind of stress to your Agave.
Magnesium plays the central core of the chlorophyll molecule that gives green color to the plant.
If the soil is deficient in Magnesium then most likely the plant will deteriorate its shape and color. (Source: University of Minnesota Extension)
Succulent plants, like any other plant, also need magnesium to retain their beautiful green color.
What to Do:
- Consider applying soluble sources of magnesium as fertilizers for succulents or indoor houseplants. The most common are Epsom salt and Magnesia.
- Agave doesn’t require too much fertilizer, so try to use it in moderation.
- Continually apply the fertilizer once every month, except for winter seasons, until the plant establishes again and the discoloration stops.
Lack of Light
Another basic thing to know in gardening is correct lighting depending on the plant that you have, and this is specifically true with your Agave.
Going back to its native environment, Agave commonly flourishes on deserts concluding that this plant needs much amount of sunlight.
Without enough light, Agave can not produce chlorophyll and perform photosynthesis. Lack of chlorophyll causes it to turn yellow.
Typically, succulents like Agave require 6 hours of sunlight to obtain their best appearance and growth.
In fact, it can survive the hottest and driest summer in the Southwestern United States. (Source: North Carolina State University)
What to Do:
- If you suspect that your plant is receiving a lack of sunlight, then the first thing that you need to do is to move it to a spot where sunlight is much abundant. Usually, the best location is on a south or west-facing window.
- Even if it’s located on a sunny spot you’ll still need to make sure that it has proper drainage, especially during cool winters.
- Though Agave is known for its drought surviving capabilities, there are still instances that your plant may experience excessive direct sunlight. This is less likely to happen, but you can easily tell if you see that some of the leaves start to drop. In that case, consider a little shading to your plant.
Temperature and Humidity
A low-temperature level and a humid environment will create moisture on your Agave’s soil thus allowing pests and fungi infestation within the root system.
This will create a shortage of water and nutrient supply which will cause yellowing on its leaves.
On a quick note, Agave prefers hotter climates with less humidity. Ideally, this plant loves temperatures that go above 100 °F (38°C) but in cooler seasons it can tolerate up to 60 °F (15°C).
What to Do:
- If you’re thinking that your temperature is stressing your Agave, conduct a temperature check in your indoor garden area. Purchasing a good thermometer is a good investment if you want your plants to receive the correct temperature.
- In case your current area isn’t sustainable in achieving the required temperature, then relocate your plant to a more suitable area. Also, consider the ventilation in the area and how frequently you’re using it since most of the time, these are the main reasons for the humidity to rise.
- If you already found the necessary spot where the temperature can most likely be maintained, then make sure to settle it and avoid excessive moving.
- Bear in mind that as long as your Agave is sustained in its temperature then most likely you’ll have no problem with humidity.
In reality, plants are not bound to be moved from one place to another from time to time. The only time that you’re bound to repot is when it grows out of its container.
Most of the time, if you do it incorrectly or carelessly, the plant suffers from transplant stress or also known as transplant shock.
This may result in not only the yellowing of leaves but also to plant wilting. In that case, you may want to take precautions and save your plant from eventually rotting.
What to Do:
- First, check if there is enough drainage in your pot. Again, Agave requires so much draining time, so it will help if you add a few more drainage holes for it to process quickly.
- Then run a temperature check in your area. Sometimes repotting means relocating your plant, if that’s the case, make sure that your location has a suitable amount of temperature. Preferably, bring it back to the same spot where it used to grow.
- Next, remove all the yellowing and dead leaves to make room for regrowing.
- Lastly, daily monitor the water and sunlight needs of your plant. Sometimes it just needs a couple of days to recover from the stress of transplanting and eventually it will flourish once again on its own.
Soil pH or soil reaction refers to the acidity or alkalinity of the soil measured in pH units. Agave will grow properly on soil that has a 6.6 to 6.8 pH level.
If it drops down below 6.6, the soil will become acidic resulting in magnesium deficiency. Again, your plant needs magnesium to avoid wilting and discoloration.
What to Do:
- If you think that the soil of your plant has a problem with its pH level, then consider buying a soil test kit at any garden store near you.
- Do not take a sample in the surface soil. Consider around 4 to 5 inches below the surface since most of the surface soil has a different pH. Remember that the roots of Agave travel at least 4 to 5 inches deep, so it’s ideal to test there.
- If the pH is above 6.8, then the soil is probably exposed to alkaline, though it’s not most likely to affect the plant, still its best to add sulfur to the soil to decrease its pH.
- If the pH is below 6.8, then the soil is acidic. Add lime to increase its pH. You can also apply fertilizers that are rich in magnesium.
- If discoloration still exists after a couple of days, consider repotting your plant to more suitable soil. Do not forget to remove the dried yellow leaves after repotting.
Root rot damages the root system. As a result, it can not intake water or nutrients for its normal physiological process. So it can cause the agave to turn yellow.
The common cause of roots from rotting is overwatering. It can give too much moisture to the roots of your plant, thus creating an ideal environment for fungus infestation.
Aside from discoloration, symptoms such as rotting, wilting, and dropping can also be recognized in your plant.
Upon checking the root, you can see that it turned soft and brown different from its usual hard and white appearance.
This is a serious case for it can bring your Agave to death in a couple of weeks if not treated immediately.
But you don’t need to be hopeless right away for there are some possible tips that you can do to save your plant.
What to Do:
- The first thing that you need to consider is checking the root. Gently detach the plant from the soil, clean away, and look for the root appearance. If it looks brown and soft, then your plant needs treatment. Otherwise, the root is healthy and you can plant it back in the pot.
- Cut off all the dead and dying roots. As much as possible you don’t want to leave any as it could potentially infect the remaining healthy roots.
- You should also cut all discolored and dried leaves. Since you removed some, if not much, of its roots then your plant’s root system is much smaller now and isn’t capable of handling a bigger plant. If you think that the roots are still not enough to handle the volume of healthy leaves remaining, try pruning it more.
- Apply an antifungal solution to the healthy roots before repotting them.
- As much as possible, it is advisable to use other pots since your old one might be contaminated. But in case you want to use the same pot, dump all the soil into the trash then wash it with bleach and hot water. Make sure that you rinse it carefully before adding clean soil and planting back your Agave.
- Allow a proper drainage system by elevating your pot or adding more holes beneath.
- You might also want to isolate your plant for a while, just make sure that it has enough sunlight
- Finally, sprinkle your plant a little.
Fungal Leaf Spot
If the discoloration of your Agave leaves comes with some brown or black spots then most probably your plant is suffering from a fungal leaf spot or somehow known as anthracnose.
This is caused by a fungus named Colletotrichum. This fungus produces spores that are distributed by splashing water or through the air.
Therefore humid and shady areas are the most vulnerable spots for this infestation to happen.
What to do:
- If you suspect your plants have fungal leaf spots, then you need to immediately isolate them to prevent the spreading of the fungus. Avoid humid or shady areas, it will be best if you placed it on a better sunspot area.
- Remove any infected leaves and be sure to dispose of those properly to avoid spreading.
- Avoid overhead watering. Use a spray to directly water the soil.
- Apply fungicides like thiophanate methyl to avoid recurring.
- If the plant is ready to leave isolation, make sure to allocate proper spacing in between pots to produce good air circulation.
When infected, you will see a flour-like substance on the stem and leaves of your Agave. It affects the process of photosynthesis that causes the leaves to fall off their green color.
Moreover, it sucks valuable nutrients from the plant, the reason why you need to act immediately.
What to Do:
- Just like any other fungus, Powdery mildew enjoys the presence of a humid environment. So in case any symptoms appear, Relocate the plant to a less humid room and allow proper air circulation.
- Check the drainage and avoid the soil from becoming wet for a long time.
- Apply a bicarbonate solution. Mix 1 teaspoon of baking soda in 1 liter of water. Then spray it on the affected leaves thoroughly.
- In case the plant is infected badly, remove all infected parts, and dispose of them immediately.
Pests may also cause the discoloration of your Agave. That’s why it’s advisable to thoroughly check the plant before purchasing to avoid bringing unwanted pests into your garden.
The most common culprit is the agave snout weevil. From the name itself, you can see that these creatures are attracted to invading your plant.
The female weevil lay eggs on the base of the plant thus sucking all the nutrients resulting in discoloration and will eventually lead to decaying
Sap-sucking insects could also be the culprit since they feed on the sap. Sap brings hydration and other efficient nutrients to your plant, so losing it would cause deterioration to your plant’s leaves.
Mealybugs, aphids, and mites are the common sap-sucking insects that you might encounter in our garden.
What to Do:
- First, check your Agave for any signs of pests infestations such as leaves turning yellow, brown noticeable spots, or leaf dropping.
- If you detected an invasion, identify first the type of pest you’re dealing with before buying any insecticides. Research on what are the safe insecticides to avoid messing up with your plant.
- Watch out for the soil’s moisture level since most of the pests easily propagate in moist areas.
- Don’t forget to remove all the infected or damaged areas to prevent spreading.
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How to Stop Your Agave Leaves Turning Yellow
Always keep in mind that preventing your Agave leaves from turning yellow is easier than curing them.
Although this situation is common for your plant, still there are ways in which you can prevent it from coming.
- Proper Buying. Make sure that the plant is healthy from all possible symptoms before purchasing it.
- Proper Sunlight. Place it in a spot where sunlight is abundant.
- Proper Water Regulation. Water it once every 5 days or until the soil dries.
- Proper Drainage. Elevate your plant a little or add more holes to your pot to help aid the draining process.
- Proper Weather Treatment. Always place your Agave in high-temperature areas especially during winter seasons.
- Proper Ventilation. Put enough space between your pots to allow air circulation.
- Proper Understanding. Try to research more about your plant to fully understand its needs.
Agave is a beautiful choice of succulents. Its unique physique and beauty will add a good landscape to your indoor garden.
Though it’s prone to discoloration, it’s still easy to deal with and maintain if you have the proper knowledge.
If your leaves are turning yellow, check for their symptoms first. If you found out the main cause, then you can properly apply treatment and possible precautions for the future protection of your plant.