Growing Carrots For Black Swallowtail Butterflies: Do Black Swallowtails Eat Carrots

Black swallowtail butterflies have an interesting relationship with plants in the carrot family, Apiaceae. There are many wild plants in this family but in areas where these are scarce, you might find the adult insects and their larvae hanging out in your carrot patch. Do black swallowtails eat carrots? Carrots and black swallowtail caterpillars have a love/hate relationship. So I guess the butterfly has the bulk of the benefits, but you get to attract these lovely pollinating insects when you grow carrots.

Black Swallowtail Butterflies and Carrots

Carrots are generally unbothered by above the ground insects but, in some regions, their foliage can be entirely decimated by the presence of black swallowtail larvae. Adult butterflies prefer nectar from various plants, but they love to lay their eggs on carrot family members and the caterpillars chow down on their leaves. If you love to attract wildlife, growing carrots for black swallowtail butterflies is a sure way to entice them.

Black swallowtail butterflies range across North America. They are lovely black and yellow butterflies with a small amount of blue and red on their hind legs. Their larvae are large 2 inch (5 cm.) long caterpillars with voracious appetites. Do black swallowtails eat carrots? No, but their offspring definitely enjoy the foliage.

Are Black Swallowtail Butterflies Beneficial?

Black swallowtails are not really harmful as adults but they don’t directly benefit any garden plants either. Their young are considered pests in large numbers, but the average hatch doesn’t kill carrot plants, just defoliates them. In time, the carrots can regrow leaves and withstand a larval onslaught.

Carrots and black swallowtail caterpillars can have a contentious relationship, but the adults simply use the plants as landing zones and a place to lay their eggs. Carrots and black swallowtail caterpillars are constant companions in late summer until the larvae pupate and overwinter.

The larvae will also be found on wild plants such as poison hemlock and queen Anne’s lace. Other plants that attract black swallowtails are dill, fennel, and parsley.

Growing Carrots for Black Swallowtail Butterflies

Black swallowtails are known for their beauty and many butterfly enthusiasts try to attract them to the garden. While providing them with colorful nectar rich flowers is a way to bring them in and feed them, uniting black swallowtail butterflies and carrots will support future generations.

Black swallowtail butterflies will appear in spring and lay their eggs on ideal host plants. Their young do cause some damage through feeding but generally not enough to permanently damage the carrot crop. Many of our native butterflies provide a picturesque way of decorating the garden, providing viewing pleasure with their gentle ways and colorful beauty.

Growing plants that are attractive as breeding areas will ensure a continued supply of these magnificent insects year after year. As an added bonus, you and your family get to watch the lifecycle of a truly interesting organism.

Controlling Overactive Populations of Larvae

In some instances, especially in commercial growing zones, large populations of the larvae may be a nuisance. In rare cases, it may be necessary to hand pick and destroy large infestations of caterpillars or use a product such as Bacillus thuringiensis, a natural bacteria that will kill the larvae.

There are also three types of tachinid flies and several other natural predators, including some birds, which feed on the caterpillars. However, the larvae emit a nasty taste and odor that repels many potential predators.

If you are not growing organically, you can also resort to a listed pesticide. Always follow directions and wait a month before harvesting any treated foods such as carrots.

Bug of the Week

Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

A female black swallowtail butterfly lays her eggs on dill.

Because many herbs are easily cultivated in small flats or pots, even gardeners with limited growing space can enjoy fresh culinary delights throughout the summer. This is one reason cultivating herbs like parsley and dill in a backyard garden or patio containers has become so popular. However, humans are not the only creatures with a taste for savory herbs. Many insects find these fresh summertime delights irresistible. A week or so ago, while plucking parsley from the parsley patch I discovered a few tiny caterpillars doing their best to imitate bird droppings. In a matter of days these tiny larvae developed into several very impressive green, black, and yellow caterpillars joyously devouring my precious herb. And now, after a couple of weeks of this caterpillar calamity, it looks like I will be buying my parsley at the market until my poor parsley plant recuperates.

Tiny bird-dropping-mimic caterpillars take tiny bites, but just watch what happens to my parsley when an almost fully grown caterpillar goes to work! (Ok, it is at double speed).

Tiny yellow, beach ball-like eggs deposited by the female butterfly soon hatch into hungry caterpillars.

This saga began several months ago, when the adult black swallowtail butterfly emerged from a chrysalis that had survived the chill of winter. Nectar and pollen from a variety of flowers sustain the butterfly in spring and summer. After mating, the female swallowtail searches for wild plants in the carrot family such as Queen Anne’s lace or cultivated delicacies including carrot, fennel, dill, and parsley. She lays a few eggs on a plant and in a matter of days these hatch into tiny caterpillars. At first, tiny black swallowtail caterpillars resemble bird droppings. As with other swallowtails we visited in previous episodes like the spicebush swallowtail, this scam may help these tiny tasty treats escape detection and death at the beaks of would-be predators like birds.

Older black swallowtail caterpillars are banded with dazzling swatches of black and yellow on a field of green. These creatures do not attempt to blend in with their surroundings. Older stages of black swallowtail caterpillars have their own clever defense to ward off enemies intent on making them a meal. Just behind the head of the caterpillar is a specialized structure called the osmeterium. While chillin’, this forked, orange appendage is tucked beneath the skin out of sight. But when the swallowtail larva is threatened, it extends the osmeterium in the direction of the disturbance. This glandular organ is coated with foul smelling chemicals, isobutyric and methylbutyric acids, with a fragrance of rancid butter. The disturbing visual and olfactory display discourages hungry predators from wanting to dine on this beautiful caterpillar. In addition to the stinky fluid from the osmeterium, the caterpillar will often disgorge its last meal to help repel an attacker.

A quick fly-over with the camera tells me the parsley is in trouble. And when you grab one of these rascals, oh watch out. If stinky fluids from the osmeterium don’t dissuade an attacker, regurgitating the last meal just might.

Serious herb growers sometimes find black swallowtail caterpillars so abundant that crops are ruined. For me, well, a little extra parsley or dill planted for caterpillars ensures that I get to enjoy the adults moseying through my flower beds, and provides the opportunity to give a caterpillar a gentle squeeze to witness the crazy osmeterium. If sharing your herbs with large gorgeous caterpillars is not exactly your cup of tea, larvae are easy to spot and can be moved out of herb garden to Mother Nature’s garden like a nearby patch of Queen Anne’s lace.

Tubular flowers like those of Vinca are irresistible to nectaring black and spicebush swallowtails.

Are Black Swallowtail Butterflies Beneficial - Learn About Carrots And Black Swallowtail Caterpillars - garden

Create a backyard butterfly habitat, and learn how to raise Swallowtail Caterpillars!

The purpose of this activity is to encourage Black Swallowtail Butterflies to visit your backyard by designing a butterfly habitat specific to their needs. You will learn which plants attract Black Swallowtail caterpillars and butterflies so they can enjoy a healthy snack fresh from your own garden. Then, you can easily observe the life cycle stages of the butterflies as they enjoy all the comforts of home in the butterfly habit YOU designed. Activity Created by Nancy Yard, RHA Volunteer and Educator

Start plants from seeds, or use plants readily available to create a butterfly garden area, by either using containers or a small plot in your backyard.

Thanks to students, gardeners, and NABA (the North Jersey Butterfly Club) the Black Swallowtail is now the New Jersey official state butterfly.

Duration: Spring through early fall.

Level: Pre K through Middle School, Families

Setting: This lesson takes place in a “garden” you will design. You can be very creative in its design and placement. The plants will adapt well to a variety of pots/containers. Full sun is the necessary component to growing strong plants and attracting butterflies.

  • Seeds: Parsley or Dill, Carrots, Zinnias, Cosmos (you can also purchase plants, which are readily available in garden centers)
    • Food sources (or host plants) for Black Swallowtail larva or caterpillars: parsley, dill and carrot tops (Other larva food sources include Queen Anne’s Lace, Fennel and Turnips.)
    • Nectar Sources for Black Swallowtail Butterflies: Zinnias and Cosmos (Other nectar sources for adult butterflies include: Bee Balm, Lantana and Coneflowers.)
  • Growing Mixture: Potting soil mix for edible crops or garden soil (Organic soil if possible.)
  • Containers for gardening and seed sowing: recycled containers such as milk cartons, egg cartons, yogurt containers, a variety of large pots or a small garden plot

Did you ever wonder what carrots, butterflies and kids all have in common? How you can help improve the habitat for our state butterfly while eating healthy yummy snacks? Enjoy gardening while exploring these questions!

1. Design Your Garden

  • Select an area that gets 6 to 8 hours of full sun
  • Select a garden spot that is approximately 4 feet by 4 feet, 4 feet by six feet, or gather three to four large containers.
  • Sketch your garden by including both:
    • (A) Nectar Plants like zinnias, cosmos
    • (B) Larva or Host Plants like parsley, carrots
  • Example Design: in ground garden or raised bed, alternating host and nectar plants

  • Containers should be large enough to accommodate healthy roots. Plants can be clustered in large containers such as barrels, buckets or bins.
    • Container sizes:
      • Carrots: 12 to 18 inches deep
      • Parsley: 6 to 12 inches deep
      • Tall Zinnias: 12 to 18 inches deep
      • Small Zinnias: 8 to 12 inches deep

Example 1: Container Garden

  1. 4 pots of Zinnias
  2. 1 Large pot of Parsley containing three to four plants
  3. 1 large pot of carrots

Example 2: Container Garden

  1. 2 cosmos
  2. 2 zinnias
  3. 6 parsley plants

Example 3: Mixed In-Ground and Container Garden

  1. Row of carrots/parsley in ground
  2. 6 pots of zinnias

2. Seed Sowing, Indoors and Out

Zinnia and Cosmos

Seeds can be started indoors four weeks before your last danger of frost. (You can find your frost date on the internet by using your zip code, however a good rule of thumb for New Jersey is May 15 th .)

Sow seeds ¼ inch deep and cover lightly. Water lightly every other day.

Seeds can be started outdoors after all danger of frost. Plant seeds in rows or scatter being sure to remove/thin or relocate plants until they are to 8 to 12 inches apart depending on variety selected.

Parsley and Dill

Plant seeds inside in individual pots six to eight weeks before final frost. Plant ¼ inch deep, cover lightly and water every other day. Thin to two three plants per pot.

*Parsley and/or Dill, Staring Outdoors:

Plant seeds directly in a the ground or pot after final frost. Plant in rows or scatter. Plant a ¼ inch deep.

Carrot seeds should be planted in the ground or in a large pots after all danger of frost. Plant in rows or scattered. Plant seeds ¼ inch deep. Cover lightly with soil. Water lightly every other day. Remove/thin plants when they are two inches tall to two inches apart.

Hardening Off Young Plants:

Seedlings (or young plants) should be moved outside to a sheltered location after all danger of frost. This allows them to adapt to wind, full sun and rain. This is known as hardening off and should last about five days to one week. Depending on sheltering conditions it is beneficial to move them outside a few hours each day and bring them back in at night. Be sure to make certain plants don’t dry out as plants adapt to the outside conditions.

No need to worry if you are late getting your plants started. Butterflies and caterpillars become more abundant throughout the summer months. Why? How does their life cycle contribute to this increase?

3. Maintaining Your Garden

  • Watering is best done early in the day. Water the soil thoroughly every few days. Pots may require more frequent watering.
  • Mulch will help maintain moisture and help prevent weeds.
  • Zinnias and Cosmos require the removal of faded flowers to encourage more blooms to attract butterflies. This is often referred to as deadheading. Deadheading can be done by pinching blooms just below the flower head or using a pair of scissors.

  • Carrots are ready to harvest when the carrot top is visible and approximately 1/2 inch in round. Gently push away the soil to view your carrot tops.

4. Observing the Life Cycle of the Black Swallowtail Butterfly

Egg Stage: Black Swallowtail eggs are small and yellow. They are laid individually under the leaf of the larva/caterpillar food source. Eggs develop in 3-5 days. If you look carefully under the leaves of your Host Plants you can see them against the green foliage.

Caterpillar/Larva Stage: The caterpillars develop into full size in approximately 10-14 days. Their appearance changes as the caterpillar grows. Look for partially eaten leaves.

The caterpillar will often move away from its food source when it is ready to become a pupa/chrysalis (stage where caterpillars chanes to adult), look for caterpillars on surrounding plants or objects.

Pupa/Chrysalis Stage: This is when the butterflies transform from the larva stage to the adult butterfly. The caterpillar attaches itself by a thread and develops in a pupa. It can be difficult to spot the pupa as when it is complete it is small and brown and blends in with the surroundings.

Butterfly Stage: Pupas formed in summer will emerge as adults, or butterflies in 10-14 days. Pupas formed in late summer, as the weather cools and the days get shorter, may over winter, or spend the winter as pupas. The butterflies will emerge in the following spring as the weather warms and nectar plants become available.

5. Rearing Black Swallowtail Butterflies

If you find an egg on your plants, you can raise the Black Swallowtail Butterflies by using a temporary holding container. This is a commitment to a living thing and must be carefully maintained and monitored.

  • Select an insect rearing tank or small fish tank.

Place the larva’s food source, or host plant, in the bottom of the tank. (This will be the plant your larva is feeding on when you discover it in your garden.) Wrap the end of the stem or leaf with a moist paper towel to help maintain freshness.

Be sure to select healthy leaves that are green and pest free. Change the food source as it is eaten and remove any frass, or caterpillar droppings, from the container.

  • Secure/prop a stick in the tank. This will support your caterpillar as it molts, or sheds its outer skin to change into a pupa, and will also support the emerging adult butterfly later.

The stick should reach the top of the container to ensure that the butterfly can fully emerge and extend its wings. The caterpillar will often make its pupa on the top of the tank so the top must be secure to hold the emerging adult

  • Cover and secure the top of the tank with a screen or other netting. Black Swallowtails are great at escaping so make certain there are not gaps or holes.
  • Place the tank out of direct sunlight.
  • Find a large Black Swallowtail Caterpillar to place in the tank. Monitor the food daily and replace to ensure freshness.
  • Once it becomes a pupa monitor for signs of emerging.

Note: If you collect your caterpillar late in the summer or early fall it will go into diapause or rest until the following spring. Your pupa continues this stage and spends the winter as a pupa, or “over winter.” Place the caged pupa in an area where it is cool and sheltered, such as a storage shed, barn or unheated garage. In dry conditions light misting is recommended every few weeks throughout the winter. Mist the container lightly. Begin checking for your emerging butterfly in April. Bring the cage out in the spring when the weather warms.

  • When your butterfly emerges, set the cage in a sunny location and remove the lid. When its wings are warm and dry your butterfly will take flight!

6. Wrapping Up:

  • What might happen if you placed several caterpillars in your habitat container to develop into butterflies?
  • Why would there be more butterflies/caterpillars visible in your “garden” in August than in June?
  • Why is it beneficial to the Black Swallowtail to have some butterflies emerge in the warm days of summer and some the following spring?

How did you like this activity? Please share any questions, comments, or photos that you and your child have on the Raritan Headwaters Learning Community Facebook Page!


They may eat some dill. But I'd gladly sacrifice the foliage for these beautiful butterflies.

Maybe pick off half of them? Likely predators will get their share too.

Rhizo_1 (North AL) zone 7

Fika, they're not harmful at all. unless you consider having your dill completely eaten to the nub a problem, lol.

Personally, I wouldn't like it very much if that happened to my only dill plant. The caterpillars are voracious. a lone individual can make a large portion of your dill disappear overnight.

The usual strategy for butterfly and caterpillar lovers is to grow lots of other plants for them to feed on. Black swallowtails use parsley, fennel and carrot tops, among others. Plant more dill, and move the cats from the your plant to the others. they won't mind.

I grow a couple of lemon trees in containers solely for the Giant Swallowtails to go crazy with during the summer. I also grow extra hosts plants for other swallowtails and even plant sacrificial tomatoes for hornworms.

But I don't feel one bit guilty about eliminating them if there are just too many and you shouldn't, either, if that's what you decide to do.

Birds don't much like swallowtail caterpillars. Their primary predators are paper wasps, who swoop down to grab the cats, sting them to paralyse, then stuff them into the nests for the wasp larvae to feed on.


Well unfortunately it is my only dill plant and I actually do use it quite frequently in my cooking (have you seen the price of fresh herbs at the market?!). I will buy a few parsley plants but for now. those caterpillars have got to go! Thank you sooooo much. you've been most helpful.


Well unfortunately it is my only dill plant and I actually do use it quite frequently in my cooking (have you seen the price of fresh herbs at the market?!). I will buy a few parsley plants but for now. those caterpillars have got to go! Thank you sooooo much. you've been most helpful.

Tiffany, purpleinopp Z8b Opp, AL

Agreed, harmful to the plant, beneficial to humans who enjoy seeing the butterflies.

I can absolutely appreciate not being willing to share your lone dill plant with caterpillars, even those that will turn into a beautiful butterfly. If possible, you could prevent access to your plant so the eggs won't be wasted on your plant. I don't know what might work specifically for you, but generally, maybe some kind of screen/wire 'house' might be possible for your dill plant? If the adults can't lay eggs on your plant, they will find another plant, (like the parsley plants you mentioned, or maybe another dill plant) where the caterpillars may have a chance to fulfill their destiny to become butterflies. This would also save you the time and aggravation of inspecting your plant for unwanted visitors and finding a way to deal with them, preventing the issue altogether. Further caterpillars would be on the parsley to begin with, no inspecting of dill needed.

One should definitely have things 'their way' in their garden, and it's not practical to share your food to the point that there's nothing left for you. The fact that you are here asking about them instead of just smashing them and moving on without further thought made me think you might be interested in this suggestion.


WHEN I TALKED to Doug Tallamy in February around the publication date of his latest book, “Nature’s Best Hope,” I didn’t want to go on and on about the advice in it regarding smart fall cleanup, which is one of the ways I know I’ve dramatically shifted the way I manage my own garden compared to 10 or even five years ago. But we were looking ahead to spring then, not fall.

I’m grateful that Doug returned to the podcast in autumn to do just that. Want to plan your most ecologically minded garden cleanup ever, and understand the consequences of each potential action you can take—including next spring?

The subtitle of University of Delaware professor Doug Tallamy’s recent book, “Nature’s Best Hope,” is “A New Approach to Conservation that Starts in Your Yard.” Meaning: The choices we make all year-round, including the very important one of how we clean up, can help counteract an overdeveloped, fragmented landscape that puts the food web to the test. You and I are nature’s best hope, and I’m glad Doug joined me again to help us learn to support it.

(Stream it below, read the illustrated transcript or subscribe free.)

Watch the video: Butterfly Gardening. How to raise caterpillars to black swallowtail butterflies

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