Why Do Your Lilacs Smell Like Mothballs?

Lilacs typically have a strong and sweet scent, and many people find it pleasant to be around them and take in their odor. However, in some situations, a strong lilac scent can be musky and unpleasant and even resemble the odor of mothballs.  

Lilacs smell like mothballs because they contain high amounts of indoles. Indole is an aromatic compound that smells like mothballs in its pure form and in high concentrations. 

In the rest of this article, I’ll explain further why lilacs occasionally smell like mothballs. I’ll also discuss how the same compound that causes the mothball odor makes lilac a popular and appealing essential oil. Finally, I’ll offer suggestions for ways to preserve the smell of lilac in your home after the growing season ends and the indole is less concentrated. 

Why Do Lilacs Smell Like Mothballs? 

Lilacs occasionally smell like mothballs because they contain an aromatic compound called indole, which is a chemical that naturally forms in many flowers. In high concentrations and in its pure form, indole smells like mothballs. 

Indole is a natural organic compound that is found in feces and many plants, including the following: 

  • Lilacs
  • Gardenias
  • Jasmines 
  • Hyacinths 
  • Tuberoses
  • Magnolias 
  • Roses
  • Honeysuckles
  • Orange blossoms

Indole’s Biological Function as an Organic Compound 

The indole compound consists of a six-membered benzene ring connected to a five-membered pyrrole ring that contains nitrogen. In plants, this compound is produced in the shikimate pathway. It is involved in various biological systems with serotonin, melatonin, and scent compounds. In plants, indole is a participant in the following functions: 

  • Trp production 
  • Biosynthesis of scent metabolites 
  • Plant growth and development 
  • Plant defense against herbivores 
  • Attracts pollinators 

Indole is used as an ingredient in many perfumes, but surprisingly, in its pure form, it smells more musty and wet, like mothballs. If your lilac plant contains a high concentration of this compound, you will likely notice this smell. 

Humidity Affects Lilac Scent

It is also more likely that your lilacs will smell like mothballs if you live in a hot and humid area. Humidity traps odor-causing molecules, which makes them linger longer and become more noticeable. The scent of lilac is the strongest in May and June when it is hot enough for the atomic particles to vaporize. Furthermore, these months are when the plant is trying to attract pollinators, in which indole plays a role.  

Indole smells unpleasant in its pure and unconcentrated form, but the scent becomes more floral and appealing in trace amounts. In fact, indole is used in many perfumes because the compound is believed to add intrigue and seduction to a scent. 

Lilac Is Commonly Used in Essential Oils 

Despite occasionally smelling like mothballs, lilacs are often used in essential oils, partially because of the presence of indole. Other active ingredients of interest include lilac aldehyde and ocimene. 

Lilac essential oil has many benefits and uses

  • Increases the rate of healing and the growth of new skin cells. Lilac essential oil contains many antioxidant properties that help speed the skin’s healing process. If you have a bruise, scrape, sunburn, or rash, applying some lilac essential oil to the area can stimulate new skin growth and help skin heal more quickly. 
  • Helps prevent symptoms of aging skin. People also apply lilac essential oil to their skin to increase elasticity and tighten the skin, which reduces the appearance of wrinkles and other blemishes. 
  • Lowers the risk of fungal infection. Lilac essential oil has many antifungal properties that help eliminate fungi from the body and prevent infections from occurring in the first place. 
  • Stimulates the release of toxins from the body. This essential oil can promote sweating, which leads to the release of toxins from the body. As a result, those suffering from infections and illnesses experience relief quicker than they would have otherwise. 
  • Promotes calmness. Just a few inhales of the scent of lilac essential oil can lower stress and hormone levels, leading to a feeling of calmness and a decrease in anxiety. Lilac essential oil is also known to help people with insomnia get better sleep. 
  • Improves room odor. Putting lilac essential oil into an oil diffuser makes the air smell fresh and sweet. The indole present in lilac oil is so diluted that you won’t notice the smell of mothballs at all!

How To Preserve the Sweet Scent of Lilacs

After May and June, the indole will likely be less concentrated, and your lilac plant will smell sweet and delicious instead of like grandma’s old couch. Because of this, you may be seeking ways to preserve the yummy scent. Here are some ideas for what you can do: 

Create a Lilac Enfleurage

Enfleurage is the process of extracting the scent of a flower using animal or vegetable fats, and it is a technique that has been used for centuries, beginning with the Romans and the Greeks. Here’s how to make it yourself: 

  1. Cut dry lilacs in the morning and remove them from the stem. Leave the leaves and other greenery behind. 
  2. Add fat or shortening to a container or a glass baking dish. 
  3. Arrange the flowers onto the shortening. 
  4. Use glass or plastic wrap to cover the top of the container. 
  5. Leave the container for twenty-four hours in a cool place. 
  6. Remove all the flowers. 
  7. Seal the shortening or fat in a jar. 
  8. Add alcohol to the jar to separate the fat from the flower oil.

Make a Lilac Facial Toner

Lilac is beneficial for the skin, so you can take advantage of this quality and the sweet smell of lilacs by making a facial toner. 

To make the toner, you’ll need a 16-ounce Mason jar. These are pretty versatile; you can use them to hold the following substances:

  • Food
  • Condiments
  • Spices
  • Cosmetics
  • Homemade candles

Once you have an appropriate container, follow these steps to make your own lilac facial toner:

  1. Fill a 16-ounce (0.47-liter) jar with lilac blossoms.
  2. Pour boiling water over the blossoms to make the toner.
  3. Let the blossoms sit in hot water for thirty minutes
  4. Strain the mixture into a bottle.

You can add the toner to your face using a cotton pad or a spray bottle. You can also use organic witch hazel for an even more effective facial toner. 

Add Lilacs to Your Food and Drinks

Lilacs are edible, and you can take advantage of this quality while continuing to enjoy the scent of lilac. One way you can do this is to make lilac-infused honey. Add the blossoms to a Mason jar, cover them with honey, and allow them to infuse to make a unique, sweet-smelling, and delicious honey that is perfect in tea or on toast. 

You can also easily make lilac water by placing a lilac blossom in a quart of water and soaking it overnight. Not only will the water taste sweeter, but the elements in the lilac will also help reduce anxiety with every sip. 

How To Make a Lilac Simple Syrup

If you’re a beverage lover, a lilac simple syrup is sure to transform the way you experience a cocktail or lemonade. Here’s how to make it: 

  1. Gather your lilac blossoms. 
  2. Remove the florets. 
  3. Place the florets in a fine-mesh strainer and rinse with cold water. 
  4. Combine two cups of water and two cups of sugar in a saucepan and bring to a boil. Boil until the sugar has dissolved. 
  5. Add the lilac florets to the sugar water. 
  6. Reduce the heat and let simmer for five minutes. 
  7. After five minutes, remove the pan from heat. 
  8. Cover the pan and let it cool. 
  9. Let the mixture sit for at least five hours for the lilac flavor to infuse into the syrup. 
  10. Pour the syrup into your fine-mesh strainer over a bowl. 
  11. When you’re done straining, pour the syrup into a Mason jar. 
  12. Keep the syrup in the refrigerator for a maximum of two weeks. 

Cut the Lilacs and Keep Them in a Vase

Finally, one of the best and simplest ways to enjoy the scent of lilac in your home is to cut them at the end of the growing season and keep them in a vase. For more, you can read my other articles: If You Cut Lilacs Will They Grow Back? or Why Do Lilacs Wilt When Cut? What You Need to Know


Lilacs occasionally smell like mothballs because they contain indole, which in their pure form and high concentrations, has an unpleasant musky smell that resembles mothballs. This odor is exacerbated in hot and humid conditions, so you’re more likely to smell the mothball scent in May and June. 

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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