Every summer we receive questions from people wanting to know “what is eating my passion flower?”. While there are many things that can eat passion flowers, the quick answer is most likely fritillary caterpillars. Often passion flower plants will go from looking perfect to full of holes seemingly overnight. While the damage can seem alarming, there is typically no reason to panic. Passion flowers are vigorous, tough plants. A large, healthy, rapidly growing passion flower can tolerate some chewing with no ill effect so long as it is not completely defoliated repeatedly.
If you see a lot of large holes in your plants and think you might have caterpillars, they are quite distinct and should be easy to find.
By the time you notice feeding damage the fritillary larvae should be quite big. The exact larvae appearance can vary a little. But, you will be looking for an orange and black caterpillar with big black spikes on it. They are really quite interesting looking creatures, and turn into beautiful butterflies.
The reason that damage seems to come out of nowhere is that larvae gets more and hungry as they grow. Fritillary butterflies will lay eggs on your plants. When they hatch out, the caterpillars will be plentiful and very tiny. Their little chewings will likely go unnoticed until the caterpillars have gotten large enough to make big holes. The point at which you see the damage, the caterpillars will probably be an inch or so long and getting close to pupating.
Before you go crazy squishing caterpillars, please listen to what we are about to say!
Passion flower species (incarnata andlutea) are the natural (and only) host plants for some fritillary butterfly species. On the east coast where Passiflora incarnata is native, the Gulf Fritillary is also native, and completely reliant upon the passion flowers for survival. It is their one and only host plant, similar to how monarchs require milkweed. The passion flower plants are adapted to being eaten by fritillary butterfly larvae. We have never had a problem with the caterpillars harming large established plants.
In fact, many of our customers purchase passion flower plants for the express purpose of using them in butterfly gardens to feed fritillary larvae. Since passion flowers are host plants, and fritillary butterflies are fairly common, most people withPassiflora incarnata or its various hybrids like Passiflora ‘Lady Margaret’ will see some caterpillar damage at some point. It is generally completely harmless.
So if the larvae are not completely defoliating your plants, please let them be.
That being said, young, small plants should be protected from defoliation as it can kill them. You can do this using row covers or picking the caterpillars off them. We do not recommend using pesticides to control fritillary larvae on passion flowers.
If you do not wish to attract butterflies to your garden, you can plant different, less desirable species instead of incarnata. Many of the non-native tropical species are less desirable or even toxic to the larvae. They are much less likely to show feeding damage, and won’t attract the butterflies like incarnata does.
Conversely, if you wish to grow passion flowers to attract fritillary butterflies to your yard, we definitely recommend planting Passiflora incarnata! While we do find caterpillars on other species. Incarnata is by far their preferred choice. Many passion flowers, including most reds and hybrids of those species are un-used and thought to be possibly toxic to the larvae. Some, like caerulea, might be able to be used by some fritillary but not others. In our experience given the choice between the 40+ varieties we grow, if incarnata is available, given the choice, our larvae avoid most everything else.
We hope that this alleviates concern over finding caterpillars or some feeding damage on your passion flower plants. We also hope that you enjoy seeing the beautiful butterflies they attract to your garden! Please sign up for our newsletter if you’d like to read more articles like this.
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