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Why Are My Yellow Mums Turning Purple?


Mums are also known as chrysanthemums. They are popular flowers. Mums have a variety of colors. As a garden enthusiast, you want your plants to survive but thrive. However, it can be quite puzzling when these yellow mums start to turn purple. We will explore the possible reasons for yellow mums turning purple and what you can do to prevent it.

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Flowers have different colors. But what causes these vivid colors? And why do flowers sometimes change color? To understand flower coloration, we need to look at the science behind it. Flowers get their colors from natural pigments. They are chemical compounds that give objects their color.

Natural Pigments in Flowers

Anthocyanins: They belong to the flavonoid family. These pigments make the flowers red and blue. You can find them in fruits, vegetables and other plant parts. The exact color depends on the pH level. Anthocyanins produce a red color in acidic conditions. They produce a blue color in alkaline conditions.

Carotenoids: Carotenoids make flowers yellow and orange. They are lipid-soluble. Carotenoids are important for photosynthesis. The color can vary depending on the pH value. In acidic conditions, carotenoids appear more orange. While in alkaline conditions, they can produce a yellow color.

Role of pH Levels in Affecting Flower Color

PH is an indicator of the acidity or alkalinity. The scale ranges from 1 to 14. A neutral pH is 7. While lower numbers indicate acidity and higher numbers indicate alkalinity. The pH level affects flower color by altering the chemical structure of the pigments.

In acidic conditions, hydrogen ions are released. The anthocyanins turn red and carotenoids appear more orange. Because the increased acidity changes the shape of these pigments. This makes them absorb light differently. The same principle applies in alkaline conditions. The pigments are altered to produce blue and yellow colors.

Why Are My Yellow Mums Turning Purple?

Nutrient Deficiencies

Impact of Nitrogen Deficiency: Nitrogen promotes leaf and stem growth. However, mums may start to turn purple if they do not receive enough nitrogen. Nitrogen deficiency can affect the chlorophyll produced. It is responsible for the green color in leaves and stems. Without enough chlorophyll, other pigments become more prominent. For example, anthocyanins. This results in the purple hue in mums.

Role of Phosphorus and Potassium: Phosphorus and potassium are also crucial for maintaining healthy plant pigments. Phosphorus promotes root growth and flower development. While potassium helps with disease resistance and overall plant vigor.

A deficiency of these nutrients can result in weak plants with poor coloration. In the case of mums, a lack of phosphorus and potassium can lead to the yellow petals turning purple. Because of the increased presence of anthocyanins.

pH Imbalance

Soil pH Influences Flower Color: pH is an important factor in determining nutrient availability. It affects the chemical reactions that occur in the soil. In acidic soil, nutrients become more soluble. For example, iron, manganese and zinc. However, these essential nutrients become less soluble in alkaline soils. They are harder for plants to access.

This imbalance can also lead to stunted growth and an overall decline in plant health. Soil pH can affect nutrient availability. Soil texture and organic matter levels also play a role.

Effects of Acidic and Alkaline Soil on Yellow Mums: In acidic soil, the purple color may appear in a blotchy or mottled pattern. Some areas of the plant show more intense purple than others. Because certain pockets of soil may have a lower pH than others. This leads to uneven nutrient availability for your plants.

In contrast, if your soil is too alkaline, the purple color appears more uniformly across the plant. Because alkaline soils have a more uniform pH throughout. This leads to a consistent lack of nutrient availability for your mums.

Environmental Stressors

Impact of Temperature Fluctuations on Flower Color: Mums are known to be hardy plants. But they can still be affected by extreme changes in temperature. They may be experiencing stress from fluctuating temperatures if your yellow mums are turning purple.

The temperature drops significantly at night or during the fall season can cause a chemical reaction within the plant. This is known as anthocyanin production. It can create purple hues in flowers. You should plant your mums in an area that provides consistent temperature and protection from harsh weather conditions.

Sunlight Exposure and Shade on Color Change: Another environmental factor that can contribute to yellow mums turning purple is sunlight exposure. These plants need plenty of light to thrive. But too much direct sunlight can cause them to turn purple.

They may start to lose their vibrant yellow color and appear more dull or pale if they are not receiving an adequate amount of sunlight. So strike a balance between sunlight exposure and shade for your mum. Make sure they get enough light without being overexposed to direct sunlight.

yellow mums

Common Pests and Diseases Leading to Color Change

Aphid Infestation: Aphids feed on the plant's sap. As they suck out the sap, they deprive the plant of these vital nutrients. This leads to stunted growth and weakened plant health. Furthermore, aphids can also transmit viruses that affect the plant's pigmentation. This causes yellow mums to turn purple.

Regularly inspect your plants to prevent aphid infestation and take immediate action. You can spray the plant with a strong jet of water or use insecticidal soap. Another effective method is to introduce natural predators that feed on aphids. For example, ladybugs, lacewings, and parasitic wasps.

If your yellow mums are already infested, you can use natural remedies to get rid of the aphids. For example, neem oil, garlic spray, or a mixture of dish soap and water. These methods are safe and environmentally friendly. This makes them an ideal solution for home gardens.

Fungal Infections: Powdery mildew is a fungal infection. It appears as a powdery white or gray coating on the leaves and stems of plants. The affected parts may turn purple, wilt and eventually die when the infection progresses. This disease is particularly common in warm and humid climates.

Fungal infections can also cause flower discoloration. The fungal spores can cause them to turn purple or brown when they land on the petals. This discoloration affects the appearance of the flower. It also weakened it and made it more susceptible to wilting.

Overwatering can create a moist environment. It is ideal for fungi to thrive in. On the other hand, underwatering can stress the plant and make it more vulnerable to diseases.

Fungal Disease Prevention: To prevent fungal infections, it is crucial to water yellow mums properly. This means watering deeply but infrequently. This allows the soil to dry out between watering sessions. Avoid getting the leaves and flowers wet while watering. Because this can promote the spread of fungal spores.

In addition to proper watering techniques, there are other measures you can take to prevent fungal diseases in your yellow mums. Fungi thrive in wet conditions. So plant your mums in well-draining soil to avoid excess moisture. Regularly remove dead or diseased plant material, as this can harbor fungal spores. Also, make sure to disinfect your pruning tools after each use.

Good air circulation is essential for preventing fungal diseases. Planting yellow mums too close together can create a humid and cramped environment, making them more susceptible to fungal infections. Give your mums enough space to allow for proper air flow.

If you notice signs of fungal infection on your yellow mums, it is crucial to act quickly. You can use a fungicide specifically designed for flowers. This helps control the spread of the infection. Follow the instructions carefully and continue treatment until the infection is completely gone.

Horticultural Practices to Prevent Color Transformation

Soil Testing and Amendment

Importance of Soil Testing: Soil testing helps to determine the pH level, nutrient levels and other important factors. Anything below 6.0 can significantly impact their color development and overall health. You need to take steps to raise the pH level if your soil pH is lower than 6.0.

How to Amend Soil? There are several ways to amend soil and control its acidity levels. You can add lime or dolomite to increase the pH level. These products are readily available at local gardening stores. You can easily apply them to the soil.

Before amending your soil, use a simple testing kit to conduct a pH test. You can determine how much lime or dolomite to add. Add small amounts at a time and retest the soil until you reach the desired pH level.

Adding compost or organic matter can also amend soil. Compost helps to regulate pH levels and provide essential nutrients to the plants. It also improves soil structure, allowing for better drainage and aeration.

Appropriate Watering Techniques

Watering Frequency: Yellow mums require consistent moisture in their soil to thrive. But not too much that it becomes waterlogged. The ideal watering frequency is once every one to two weeks. You may need to water more frequently if you live in a hot and dry region. Less watering may be required if you reside in a cool and humid climate. Keep an eye on the soil moisture level. Determine when your mum needs water.

Amount of Water: When watering mums, strike a balance between too much and too little water. Overwatering can lead to root rot and other fungal diseases. Underwatering can result in wilting and stress on the plant. This leads to color transformation. Ensures the plant receives adequate moisture without becoming waterlogged.

Importance of Well-Draining Soil

Testing Soil Drainage: You can perform a simple test to determine the soil. If the water is drained within an hour, your soil is well drained. If the hole is still filled with water after an hour, your soil is not draining correctly. You may need to amend it.

Amending Soil for Better Drainage: If your plant mums in poorly draining soil, you can amend it to improve drainage. Adding organic matter can help loosen heavy soils and increase their ability to drain water. For example, compost or peat moss. You can also mix in coarse sand or perlite to create air pockets in the soil. This allows excess water to flow out.

Container Planting: If you are growing mums in containers, choose a well-draining potting mix. Regular garden soil may not provide enough drainage for potted plants. This leads to waterlogging and root rot. Look for potting mixes specifically formulated for container gardening. Or make your own using a combination of peat moss, perlite, and vermiculite.

Choosing the Right Location

Selecting the right location to prevent color transformation of yellow mums. Choose an area with a good amount of sunlight. This will help the plants produce more chlorophyll and maintain their color.

Additionally, it’s important to consider the shade patterns in your garden. If you plant yellow mums in an area with inconsistent or dappled shade, they may not receive enough sunlight. They potentially turn purple due to increased anthocyanin production.

Using mulch around your plants to prevent yellow mums turning purple. Mulch helps regulate soil temperature and moisture levels. They are key factors in maintaining the yellow color of your plants.

The soil can become too cold for mums to thrive during fall when temperatures drop. By adding mulch around the base of your plants, you can help insulate the soil and keep it at a more consistent temperature. This will prevent the production of excess anthocyanins and minimize color transformation.

Mulch also helps retain moisture in the soil. It is important for mums to maintain their yellow color. If the soil becomes too dry, the plants may become stressed and start producing more anthocyanins. This results in a purple hue.

yellow mums in pots

Steps to Restore and Enhance Yellow Mums' Color

pH Adjustment

Lower Soil pH: Add elemental sulfur gradually lowers soil pH. Apply it according to package instructions based on initial pH readings. You can mix pine needles or peat moss into the soil to lower pH levels.

Raise Soil pH: Add lime is a common method for increasing soil pH. It is best to follow package instructions based on initial pH readings. Wood ash is a natural way to increase pH levels. But you should use it sparingly as it can quickly change soil pH.


Choose an NPK Ratio of 10-10-10: The product contains equal amounts of nitrogen, phosphorus and potassium. This balance is essential for promoting healthy growth and vibrant flowers.

Apply Fertilizer in Early Spring: When mums start to come out of dormancy and will benefit from a boost of nutrients. You can also apply fertilizer in the fall after flowers have bloomed. But avoid fertilizing during the summer as it may result in leggy growth.

Follow Package Instructions for Application: Be sure to read and follow the instructions on your fertilizer product carefully. Over-fertilizing can cause more harm than good, so it's important to apply the right amount.

Pruning and Deadheading

Use Clean and Sharp Rruning Shears: It's important to use clean and sharp tools to avoid damaging the plant. Sterilize your pruning shears with rubbing alcohol before using them.

Cut Off Dead or Discolored Flowers: This will stimulate the production of new, healthy blooms. Be sure to remove all parts of the flower, including the stem.

Deadhead Regularly: It's important to remove dead flowers regularly to keep the plant looking vibrant and encourage new growth. Aim to deadhead every 1-2 weeks.

Prune in Early Spring or Late Fall: You can also prune your mums in early spring before new growth appears or in late fall after flowers have finished blooming. This will help maintain the plant's shape and encourage healthy growth.

Prune for Size and Shape: If you want to control the size or shape of your mums, prune accordingly. You can cut back the stems by 1/3 to 1/2 to promote fuller growth.


Why do yellow mums turn purple? We have explored the reasons for yellow mums turning purple. It is important to summarize and emphasize the key factors that contribute to this color change. Additionally, proactive care and horticultural practices will be highlighted as crucial steps in maintaining the vibrancy of your flowers.

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