Hey there, garden friends! Have you ever walked out to check on your tomatoes and notice that entire stems were stripped bare of their leaves? Upon further inspection you may have spotted what looks like a green alien creature munching away on your precious plants? Yep, we’ve all been there—you’ve just met the infamous hornworm!
Here at We Sow We Grow, we’re all about understanding our garden pests visitors, even the ones that make us want to yell into the void sometimes. So let’s chat about these fascinating (yeah, we said it – fascinating!) yet destructive caterpillars that seem to appear out of nowhere and turn our tomato leaves into Swiss cheese, or overgrown grass blades, overnight.
For many home gardeners, the sight of a hornworm on their prized tomato plants can trigger immediate alarm. These large, very hungry caterpillars can certainly be destructive, but they’re also necessary creatures with an important place in our ecosystem. This post will attempt to explain several things:
- the lifecycle of both tomato and tobacco hornworms,
- their impact on home gardens, and
- strategies for either preventing damage or coexisting with these polorizing insects.
Which Hornworm is hanging in your garden: Tomato vs. Tobacco
Although often confused for one another, tomato hornworms (Manduca quinquemaculata) and tobacco hornworms (Manduca sexta) are actually distinct species with subtle differences:
Tomato Hornworms:
- Feature eight V-shaped white markings along their sides
- Have a dark blue or black horn at the rear
- Green body with diagonal white stripes
- Typically found on tomato plants, but also enjoy eggplants, peppers, and potatoes
- Found from northern Mexico to the southernmost region of Canada.
- Moths have 5 spots on their abdomen.
Tobacco Hornworms:
- Display seven diagonal white stripes on their sides
- Sport a curved red horn at their rear end
- Slightly lighter green coloration
- Commonly found on tobacco plants but also feast on tomatoes and other nightshades
- Moths have 6 orange spots on their abdomen.
- Found from Canada to Florida, USA, and extend their range into Mexico, the Caribbean, Central America, and parts of South America.
- More common in the southern region, especially the Gulf Coast.
Both of these caterpillars love our plants in the Solanaceae family such as tomatoes, peppers, eggplants, potato and tobacco plants. And honestly, most gardeners just call them all “hornworms” and deal with them the same way. No judgment if you can’t tell them apart, they can be creative that way.
The Lifecycle of the Hornworm
Let’s follow the hornworm through their life journey, shall we? Because we’ve gone through most of these human stages, we’re going to equate the lifecycle of these caterpillars with our lifecycle the best we can.
Baby Stage (Eggs) Remember those tiny, pale green dots on the undersides of your tomato leaves? Those are hornworm eggs laid by a large moth that visited your garden at night. Each female moth can lay up to 2,000 eggs.
Hungry Teenager Stage (Larvae) This is when we usually discover them—when they’re big, green, and eating machines! They start out tiny (about the size of a grain of rice), but grow FAST. Within 3-4 weeks, they’re the size of your pinky finger or bigger. They molt between 4 to 5 times during this stage. This is their teenage and most destructive phase, and just like human teenagers, their appetites are voracious, and they can consume a large amount of foliage. If you find that they are hard to see during the day, try venturing out at night with a UV light and shine it on their preferred plants, they’ll glow, and can make pest control easy.
Transformation Stage (Pupae) When they’ve eaten their fill, hornworms drop to the ground and burrow into the soil. Here’s where the magic happens—inside a reddish-brown shell under the soil, they completely transform themselves. In summer, this takes a few weeks, but in colder areas, they might stay underground all winter. These often look like a rolled up set of leaves, but if you pick them up to inspect them (try it gently) you can see all of the developing parts of the soon to be moth – including the proboscis which is the ‘stem’ of the pupal cocoon.
Flying Adult Stage (Moths) The final transformation reveals a gorgeous sphinx moth (also called hawk moths or hummingbird moths). These large, fast-flying moths with 4-5 inch wingspans visit our gardens at dusk. Ever seen what looks like a small hummingbird visiting your flowers in the evening? That might actually be one of these moths.
The Hornworm Dilemma: Friend or Foe?
Real talk, finding hornworms in our gardens often feels like defeat. Discovering these unwelcome guests can make us angry, frustrated, or even a bit afraid. But there’s more to the story:
Why We Sometimes Get Frustrated:
- One hungry hornworm can strip a tomato plant crazy fast
- They’re masters of camouflage (how does something so big hide so well?!)
- They don’t just eat leaves—they’ll go after stems, flowers, and even green tomatoes
- Young plants can be completely wiped out by just a few caterpillars
Why We Might Consider Giving Them Some Grace:
- Those hornworms transform into sphinx moths—important nighttime pollinators
- Many birds rely on caterpillars like these to feed their babies
- When you see a hornworm covered in small white cocoons, that’s actually a good thing! Those are beneficial braconid wasp cocoons—nature’s pest control at work
- They offer an amazing opportunity to show kids the miracle of metamorphosis
Finding Balance: How We Handle Hornworms
In the We Sow We Grow community, we’ve heard and tried it all when it comes to hornworms. Here’s what works for us and our community members:
Deterring Them To Start
Soil TLC
Mix up your soil in late fall or early spring to disrupt those pupae sleeping underground. We’ve found that chickens are excellent helpers with this job. They’ll gladly hunt for those pupae like they’re searching for buried treasure. We know that this may be a controversial take in a lot of gardening groups especially in regard to pollinators, so you can restrict this type of action to areas where your nightshades were planted in general.
Companion Plant Friends That Help
Our sowers and growers love planting basil, marigolds, and dill alongside our tomatoes. Not only do they make a beautiful garden, but these fragrant plants seem to confuse the adult moths looking to lay eggs.
Physical Barriers
Some of us use floating row covers until our tomatoes start flowering. Just remember to remove them when flowers appear so bees and beneficial butterflies can get in there to pollinate.
Spotting Them Before They Take Over
Take your daily garden walk
Make checking your plants part of your morning or evening routine. Grab your coffee or evening beverage and take a stroll through your garden, not just to admire your plants, but to flip over a few leaves and check for early signs of these hungry visitors. Not only is this a great way to learn your growing space, it’s a fantastic way to start or end your day in a relaxed manner.
What Should You Look For?
- Little holes starting to appear in leaves
- Black droppings on leaves (hornworm poop is a dead giveaway!)
- Missing leaf edges that look freshly eaten
- Stems stripped of their leaves starting from the top
When You Find Them: Options For Every Grower
The Relocation Program
Many folks in our community simply pluck them off and move them to a separate “hornworm plant” or trap plant away from their main garden. Others relocate them to wild areas with plenty of weedy nightshades for them to munch. Our preferred method is to relocate them into our chicken run so our feathered ladies can have a great snack!
Letting Nature Work For You
Remember those white cocoons we mentioned? If you spot a hornworm covered in what looks like grains of rice, let it stay put. Those are braconid wasp cocoons, and that hornworm is helping you grow more beneficial insects that will help control future pest problems. It’s a gnarly looking thing the first time you see it, but you’ll learn to appreciate it. We think.
Organic Solutions
If it looks like your garden has been taken over by a small army of hornworms, you can use one of these options:
- BTk (Bacillus thuringiensis var. kurstaki) is a naturally occurring bacteria that only affects caterpillars and is safe for other insects, pets, and people
- Sprinkle diatomaceous earth around the base of plants to deter caterpillars when they try to pupate
- Invite paper wasps to your garden (yes, really!)—they’re excellent hornworm hunters
Embracing The Whole Cycle
Some of our more adventurous We Sow We Grow members have tried:
- Planting extra “hornworm welcome” tomato plants just for these caterpillars – we refer to them as trap plants – if you want to be nicer than us, have at it.
- Raising hornworms in jars with their kids to watch the transformation process
- Photographing and journaling the whole lifecycle as a homeschool science project
Share Your Hornworm Stories With Us!
We’d love to hear about your experiences with these garden visitors! Have you found a creative solution? Did your kids name a particularly memorable hornworm? Did you manage to photograph the beautiful sphinx moth it turned into?
Remember, every garden is a relationship between us and nature. Sometimes that means setting boundaries with certain creatures, and sometimes it means making space for the whole beautiful, messy cycle of life.
Whether you decide to relocate every hornworm you find, give your chickens a treat, or designate a special plant just for them, you’re part of our growing community that’s learning to work with nature instead of always fighting against it.
Keep sowing and growing, y’all! And may your tomatoes be plentiful – even with a few hornworm visitors along the way.
