Exuberant Endangered Petunia

Every year at this time the North American Rock Garden Society seed exchange list arrives, and I always pore over it way too long making a wish list of plants to populate my garden. Over the years I’ve found many treasures, an inexpensive way to try assorted plants in my many gardens. Earlier this week I submitted my requests from the latest list and look forward to the arrival of tiny packets of promise arriving early next year.

This list also prompts me to think about the exciting finds I have made from this same list in previous years. Two years ago, I was intrigued by a plant new to me that popped up, Petunia exserta. At first glance from the genus, I wondered why this would be on such an esoteric list. My mental image of petunias is in large flats at big box stores, one of the most common of species with no need to painstakingly grow it from seed. This seemed the exact opposite of the often finicky and almost impossible to grow rock garden specialties that populate most NARGS lists.

As I researched, it quickly headed toward the top of my list. It is endemic to southern Brazil and was only first described to science in 1987. A return expedition 20 years later found only 14 plants left in the wild. I’m always intrigued in playing my part to save endangered species, so I was thrilled to try it.

Observing their progress after planting, I was surprised when so many seeds came up. I reached out on a gardening forum and others had experienced similar success. Because of this, I have restricted them to my window boxes, not wanting to create the next kudzu of the south. Though they died back last winter, they came back in larger numbers this spring. These returning plants are most likely from seeds since they are not hardy where it drops below freezing.

As might be guessed from the shape and bright red color of these flowers, they are unique among Petunia species in being pollinated by hummingbirds. Since hummingbirds don’t have a good sense of smell, these flowers therefore lack the typical strong floral scent of other petunias which are pollinated by bees or moths. Most of the window boxes on my porch are dedicated to providing treats for hummers and other pollinators, so I am always searching for plants they might enjoy. This Petunia seems to be a magnet for my hummers, and I enjoy the odd pleasure of watching them sip what should be an impossibly rare delicacy slowly slipping away thousands of miles away.

It is threatened in the wild largely by its extremely limited distribution, which means any habitat loss or change in climate amplifies the stress to this vanishing plant. In the wild they can hybridize with other petunias, especially Petunia axillaris, which is helping to accelerate their extinction as their genes are being diluted over time. Because of this, it is my only Petunia to avoid creating hybrids on my porch. I would like to do my small part in keeping this species from extinction.

Though it is unlikely they will survive much longer in the wild, they are a success story of sorts. Based on communications I’ve had with gardeners far and wide, they seem to be happy in gardens all over the world. My petunias are fading now from the cold weather, but I anticipate their return in spring. Given how they are thriving here I continue to contain them in my window boxes. But I imagine they are now just biding their time in the quiet way of all plants, anticipating taking over the world, one yard at a time.