Why Are My Lupin Leaves Turning Yellow? [Reasons & What to do]

Keeping house plants has exploded in popularity recently. They have many benefits, from providing beautiful home decor to filtering contaminants out of the air. Unfortunately, lupins (which are popular houseplants) have a tendency to develop yellow leaves.

Your lupin plant’s leaves are turning yellow due to root rot, a lack of nutrient-rich soil, soggy soil, or being in a pot that’s too small. Luckily, you can fix yellowing leaves by replacing the soil, adding nutrients, or moving your plant to a bigger pot, among other solutions.

The lupin, a beautiful purplish plant, can be found west of the Cascade Mountain Range, near Bend, Oregon, and even in the Deep South, such as Louisiana. Its beauty has made it a popular landscaping and garden plant. However, outside of its natural environment, it can become susceptible to disease and yellowing.

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Reasons Your Lupin Leaves Are Turning Yellow

In order to properly care for your plant and avoid things like yellow leaves, you need to be aware of the basics. Lupins have the potential to be gorgeous house plants or landscape plants, but you need to be mindful of how to take care of this perennial plant.

Below are some common reasons your lupin’s leaves are turning yellow:

Poor Drainage

If you keep your lupin as an indoor house plant, you must ensure your pot has a proper drainage system. The easiest way to do this is to purchase a planter with holes in the bottom for drainage.

If you want to take it a step further, you can add a gravelly substrate to the bottom of the pot to allow the water to drain away from the roots more efficiently.

On the other hand, if you’re planting lupins outside to give your garden a pop of color, make sure that they aren’t on low ground where water can collect around them. Planting them in a flower bed will ensure they’re on higher ground.

Over or UnderWatering Your Plant

Even though lupins love moist soil, if the soil retains too much moisture, it could lead to root rot. When the roots die, they can’t withdraw nutrients your plant needs from the soil, leading to yellow and dead leaves and potentially killing your plant.

Create a watering schedule to ensure that you don’t over or underwater your plant. Ideally, lupins should be watered every few days.

Temperature Fluctuation

Lupins adapt quickly to their environments. They can usually handle seasonal weather changes very well. Still, suppose the temperature drops below 32 degrees Fahrenheit (0 degrees Celsius) or climbs above 86 degrees Fahrenheit (30 degrees Celsius). In that case, the plant will suffer, and the leaves will begin to die and turn yellow.

Additionally, lupins do not like humidity. If you keep your lupin indoors, be sure to place it near a window where the air tends to be less humid.

Lack of Light

Lupins enjoy full sun and will grow vibrant petals and leaves if they are allowed to bask in the sun.

Make sure your lupin is sunning for at least six hours a day. If you start to notice yellow leaves, this could be the culprit. Try timing exactly how long your plant can bask in the sun. If it’s any less than six hours, move it to a different area in your house or replant it where it can get more sun.

Nutrient Deficiency

If there are no nutrients in your soil to nourish your lupin, the leaves and flowers will eventually yellow, wither and die. Thankfully, there are many cheap ways to inject nutrients into the soil. You can buy fertilizer off the shelf or use some everyday household items to provide compost around your plants.

Common household items can infuse nutrients into the soil and bring your lupin back to life. Most people are shocked that common foods, like eggshells and banana peels, can nourish their plants.

Common household foods to mix into your lupin’s soil include:

Coffee grounds – Coffee grounds can add nitrogen to your soil but it can acidify it. Lupins don’t mind acidic soil, but it would be best to sprinkle the coffee grounds into the soil and mix it in.
Wood ash – Wood ash can add potassium to your soil. Make sure that the ash is from an untreated hardwood log because any chemicals or treatments would be detrimental to your lupins.
Eggshells – Calcium is vital to the growth of your lupin, and eggshells contain plenty of calcium. Crush your dried egg shells and mix them into the soil around your plant. You can also soak them in water and use this to water your plants for a quick calcium boost.
Banana peels – You can bake and crush banana peels to add some potassium to your soil. They can also be buried at least six inches below the soil.
Used matches – Matches are great for soil as they contain a small amount of magnesium and wood, both of which are good for soil and plants.
Vegetable scraps – Vegetable scraps (whether they are cooked, raw, or rotten) will decompose quickly, and release various nutrients into your lupin’s soil.

The Soil Type Is Incorrect

The lupin’s native territory is in North America. They can be found as far north as Maine, stretching south to Florida, and as far west as Wyoming and Colorado.

Despite their variety in habitat, they enjoy moist soil. In fact, this is one of the most critical aspects of a healthy lupin plant, as they have a single taproot or a long tapering root that reaches deep into the soil. Instead of having small branches of roots reaching multiple levels of the soil, a tap root is a singular root that grows deep into the soil.

You also need to make sure your pot has sufficient drainage capabilities. If water gets trapped, it can lead to soggy soil and root rot.

Your Lupin Has a Viral Infection

Unfortunately, our beloved household plants can sometimes succumb to viral infections and fungi.

I’ve listed a few of the most common viral and fungal threats to your lupins to help you determine what is causing any discoloration or rot:

Bean Yellow Mosaic Virus – This virus is brought to lupins from aphids, also known as a plant louse, from clover patches. It will cause your lupin’s stem and leaves to turn yellow and flop over, and eventually die.
Brown spot fungus – If your plant starts developing brown spots on its leaves and stem, you have a case of brown spot fungus. Your best option is replanting your lupin in a different pot with new soil or a separate garden area. The fungus develops from spores in the soil; unless you move the plant or replace the soil, your lupin will continue to grow the fungus.
Pests – Snails, aphids, and slugs are the most common pests you will find on your lupins. The best way to prevent these critters from attacking your plants is to treat them with pesticides or some organic insecticide, depending on your preference.
Powdery Mildew – Due to over watering, this grayish white powder can form on specific areas of your plant and hinder sunlight absorption. If left too long, your leaves will begin to turn yellow and die. Ensure that you water around the base of your plant only and clip away the affected areas.

How Do I Fix Dying Lupin Leaves?

You can fix dying leaves by repotting your plant, clipping dying leaves, replacing soil, or adding some fertilizer for more nutrients. If there are a couple of yellowed leaves, you can cut them. However, if the whole plant is dying, repot it and replace the old soil with new, nutrient-rich soil.

Removing the affected leaves is a quick and easy fix, and will make room for new and healthier leaves to grow.

However, if you notice that most of your lupin’s leaves are dying, you should repot it as soon as possible. You can do this by loosening the soil around the lupin, removing it from the pot, and gently brushing any remaining soil from the roots.

After this, you can replant your lupin in good-quality soil that can promote healthy growth. Adding fertilizer can enhance plant growth and give it additional nutrients.

Think Before You Plant

While it is true that lupin are beautiful plants, they’ve recently been causing a lot of damage around the United States as an invasive species. Due to their beautiful purple color and multiple flowers per stem, they’ve exploded in popularity as a landscaping plant.

However, outside their natural environment, they can wreak havoc on other natural areas. For example, they can outgrow native species and take up the resources they need to thrive.

Final Thoughts

Lupins are beautiful, hardy plants that will liven any home or garden with their vibrant color. However, they’re still susceptible to diseases and problems that cause yellow leaves.

Make sure you water them regularly and keep the soil moist. It’s also essential to ensure the water drains properly. Lastly, take note of the easy ways to inject nutrients into the soil and ensure your lupin has sufficient nutrients in the soil.