Hairy Wild Petunia (Ruellia humilis)


Hairy Wild Petunia is a short perennial wildflower native to the Central United States. Scientifically known as Ruellia humilis, it grows 6-12″ tall in full sun and well draining soil and blooms lavender-purple funnel shaped flowers from May through September. Attractive to bees and butterflies, it self-seeds but can make a great native groundcover.

A small native planting near my mailbox. Hairy Wild Petunia in the foreground.

NOTE – I’m going to be using ‘Hairy Wild Petunia‘ to describe this flower rather than the more commonly used and simpler term ‘Wild Petunia‘. I’m doing so because there are several other members of the Ruellia genus that are also commonly called ‘Wild Petunia’ and look similar (although their height/growing conditions are different). To make matters worse, all of these members have overlapping, or near-overlapping ranges!

In this article:

What is Hairy Wild Petunia

A true native ground cover, Hairy Wild Petunia is a short perennial that grows just 6-12″ tall (15-30 cm) that blooms attractive purple (petunia-like) flowers and attracts numerous species of bees. It really is an attractive flower, and has a curious characteristic in that it’s flowers only bloom for a single day. They open in the morning, and fall off by dusk, only to be replaced the following day by new blooms. [1][2]

It can be aggressive in formal flower beds that have lots of space between plants, as it will launch it’s seeds a short distance away as the capsules dry. It establishes quickly, blooming the first year grown from seed.

Native Range of Hairy Wild Petunia

The native range of Hairy Wild Petunia is primarily the American Midwest, from South Texas north to Nebraska, Iowa, Wisconsin. Many isolated pockets also exist from Pennsylvania to South Carolina/Georgia and Alabama.

Native range of Hairy Wild Petunia, Ruellia humilis. Source [1]

Natural Habitat

Hairy Wild Petunia naturally grows in open meadows, along forests, roadsides, glades, cedar glades, and near railroad tracks. The primary limiting factors are that it will not tolerate areas prone to flooding, or competition from other plants that are significantly taller.

Hairy Wild Petunia Reference Table

Scientific NameRuellia humilis
Common Name(s)Hairy Wild Petunia, Wild Petunia, Fringeleaf Wild Petunia
Native Range, USDA ZoneCentral North America, USDA Hardiness zones 4-8
Bloom TimeJune-September
Bloom Duration, Color2-3 Months, Purple to lavender
Height6-12″ (15-30 cm)
Spacing / Spread12-18″ (30-45 cm)
Light RequirementsFull or partial sun
Soil TypesSandy, rocky, clay-loam, loam. Must drain well
MoistureMoist to dry
Fauna Associations / Larval HostsBees, Butterflies / host of Common Buckeye
References [1][2][3][4]

What are the Benefits of Hairy Wild Petunia

Beauty

The numerous lavender blooms make for a showy display. Hairy Wild Petunia does great for being the ‘front row’ of a flower bed, with taller flowers behind it, helping to provide a ‘cascade’ bloom.

Ground Cover

It’s short stature and self-seeding make it an excellent native ground cover. It will fill in a bare flowerbed, or sidewalk border nicely. Combined with Wild Violet, one could make native groundcover garden that blooms from Spring to nearly Autumn.

Long bloom duration

Blooming from late Spring until late late Summer mean you get color for an extraordinarily long time for a perennial.

Grow and Care for Hairy Wild Petunia

Sunlight Requirements

For sunlight, Hairy Wild Petunia will prefer full sun, which is at least six hours of direct sunlight. But it can also tolerate partial shade, which is 4-6 hours of direct sun per day.

Soil Requirements

There really aren’t many soil requirements, as it can grow in just about any soil that drains well. So, sandy, rocky soil, clay loam are all fine. Just make sure your soil isn’t constantly saturated.

Moisture Requirements

When it comes to moisture Hairy Wild Petunia isn’t picky – it can grow just fine in moist to dry soil. Again, just make sure it drains.

Maintenance

The primary form of maintenance for Hairy Wild Petunia is to pull unwanted seedlings. The seed capsules will burst, flinging seed a short distance away from the plant.

I’ve found pulling unwanted seedlings to be entirely manageable. But like most garden chores, you must stay on top of it.

Fertilizer

Hairy Wild Petunia does not require supplemental fertilizer. It will grow just fine in poor, inorganic soils.

How to Grow Hairy Wild Petunia from Seed

Hairy Wild Petunia will require sixty days of cold stratification to break dormancy. This can be achieved artificially in the refrigerator, or by Winter Sowing the seed. [5]

Process to germinate Ruellia humilis seed

The following steps assume you are going to sow either stratified seed, or are Wintersowing.

  1. Fill a suitable container with moist potting soil. Leave 1/2″ gap to the top edge.
  2. Place 3-5 seeds on the soil, press firm.
  3. Cover with a light dusting of soil.
  4. Place the container in a location that receives morning sun and afternoon shade.
  5. Germination should take place once temperatures warm up above 70F, or within 2-3 weeks of planting stratified seed.
Hairy Wild Petunia seedling (Ruellia humilis)

Direct sowing

You can direct sow Hairy Wild Petunia seeds. Simply scatter seed on a disturbed site, and walk or drive over the area. Do this in Autumn before the ground is frozen.

Establishment

Hairy Wild Petunia will typically bloom the first year after germination. It will not reach it’s full size until it’s second year though.

Identification and Characteristics of Hairy Wild Petunia

Stalk

A short 6-12″ stalk, it will be hairy and light green with branching in the upper third portion.

Leaf

Opposite lanceolate-shaped leaves 1-2.5″ long by 1″ wide occur in pairs along the stalk. They generally have smooth margins and are quite hairy (as are the stems/petioles).

Flower

Purple to lavender funnel shaped flowers occur near the top and are generally 2″ diameter and long (5 cm). The flowers have 5 lobes, resembling petals. Blooming generally lasts two to three months beginning in late Spring to early Summer.

An interesting characteristic is that flowers last for one single day! They open in morning, and fall off at night, only to be replaced the following day.

Cleistogamous Flowers

In addition to the showy lavender flowers, Hairy Wild Petunia will also produce cleistogamous flowers. Cleistogamous flowers are small closed flowers that never open, with the capacity to self-pollinate and produce seed. Cleistogamous flowers begin producing in mid-Summer, but will often continue until late Summer/Fall. [6]

How to save seed

Pollinated flowers will have capsules form over the course of a month. These small capsules will continue one or more seeds. Seeds can be collected just as the capsule begins to turn brown, and can be stored in an envelope in a cool dry place.

To harvest seed, one should place a mesh bag over the stalk/capsules, as Wild Petunia will fling it’s seed a short distance away from the flower (not unlike Partridge Pea).

Root

Hairy Wild Petunia has a fibrous root system.

Wildlife, Pests, and Diseases associated with Hairy Wild Petunia

Pollinators

Long tongued bees such as bumblebees and leaf-cutters will visit, as well as sweat bees, long-horned bees, and pollinating flies. [pollinators] Butterflies such as the fritillary have been known to visit, and it is also host of the Common Buckeye (Junonia coenia). [2][3][4]

Speaking of bees though, I do have to note a ‘strange’ behavior that I have observed regularly, but not seen documented anywhere else. I have seen (and have video) of large bumblebees visiting the base of the flowers. What they do is land on the mouth of the flower, then walk back to the base. I believe they are tearing into the corolla to access the nectar. This is similar to what they do at Blue Lobelia flowers, or sometimes Cardinal Flowers.

A Bumblebee who is interested in the base of the flower.

Larvae of the moth Tripudia rectangula will eat the seeds, preferring it to other species of flowers. Seed predation has been observed to range from 5-70% of available fruits.[6][7]

Pests

Deer and Rabbits

It has been documented that deer will browse the foliage of Hairy Wild Petunia. It is thought that this may be one of the risks for small populations that still exist in Pennsylvania. [3]

So, until established, or even after, you may find you need to protect your plants with Liquid Fence.

Disease

Hairy Wild Petunia is not bothered by disease. It generally looks all year. I’ve never seen any kind of foliar disease or fungus on it.

Where you can buy Hairy Wild Petunia

Hairy Wild Petunia is not typically sold in big box stores or most nurseries. But it can be purchased at specialty nurseries that deal in Native Plants. You can find native plant nurseries near you on our interactive map.

Where to buy seeds

We have ordered a variety of native flower seeds from Everwilde Farms, which you can order right from Amazon through our link on our RECOMMENDED PRODUCTS PAGE. (We may earn a small commission when you purchase through our links, at no cost to you. This helps support our website.)

Uses of Hairy Wild Petunia

Garden Uses

Hairy Wild Petunia makes an excellent ground cover. Provide it with a border of some kind such as rock, brick or a sidewalk and it will fill in nicely. This could be a great choice for a ‘hellstrip’.

Hairy Wild Petunia along my street.

Due to it’s self seeding, it may not always be the best choice for a formal mulched flowerbed where the plants are spaced apart. It can be done, you just need to be aware that you will have to pull unwanted seedlings.

It also can be used in a short to medium height meadow, border garden, or rock garden.

Companion Plants

For companion plants, Wild Petunia can grow with anything that likes full sun and well drained soil (which means almost anything!). It is often found growing amongst other short natives such as Tennessee Coneflower and Narrow Leaf Coneflower.[8]

Hairy Wild Petunia , Prairie Phlox, and juvenile Pink Muhly in the background

Some examples that will grow well with it and bloom before Wild Petunia:

For some plants that will bloom concurrently, or into Fall that have similar growing conditions:

Medicinal Uses

Hairy Wild Petunia was not used by Native Americans. At least I was unable to find any documentation. Nor was I able to find any reliable cases of it being used herbily.

Final Thoughts

For a showy groundcover, it is hard to beat Hairy Wild Petunia. The shortest of the common ‘native petunias’, it is basically carefree outside of pulling unwanted seedlings. But, these are easily managed.

I’m very happy I tried out this plant, as I’ve found it to be a very enjoyable plant to grow. It looks great most of the year, providing low lying color around flowerbeds, and being utilized by various bees (particularly bumblebees).

Find more native plants here

References:

[1] – USDA NRCS – Ruellia humilis. Accessed 19DEC2022

[2] – Holm, Heather. Pollinators of native plants: attract, observe and identify pollinators and beneficial insects with native plants. No. 595.79 H747p. Pollination Press, 2014.

[3] – Tripp, Erin A. “The Current Status of Two Rare Species of Ruellia (Acanthaceae) in Pennsylvania.” Bartonia, no. 62, 2004, pp. 55–62. JSTOR, http://www.jstor.org/stable/41610107. Accessed 21 Dec. 2022.

[4] – Robertson, Charles. “Flowers and insects; lists of visitors of four hundred and fifty-three flowers.” (1928).

[5] – Baskin, Jerry M., and Carol C. Baskin. “Temperature relations of seed germination in Ruellia humilis, and ecological implications.” Castanea (1982): 119-131. Accessed 22DEC2022

[6] – Clark, Julia, and Janette Steets. “The role of predispersal seed predators and their parasitoids for Ruellia humilis reproduction.” Research Reports from Life Science Freshmen Research Scholars 2.1 (2016). Archived 21DEC2022.

[7] – Rathcke, Beverly J. “Insect-Plant Patterns and Relationships in the Stem-Boring Guild.” The American Midland Naturalist, vol. 96, no. 1, 1976, pp. 98–117. JSTOR, https://doi.org/10.2307/2424571. Accessed 21 Dec. 2022.

[8] – Walck, Jeffrey L., Thomas E. Hemmerly, and Siti N. Hidayati. “The endangered Tennessee purple coneflower Echinacea tennesseensis (Asteraceae): its ecology and conservation.” Native Plants Journal 3.1 (2002): 54-64.

Joe Foster

Hi - I grew up outdoors in nature - hiking, fishing, hunting. In high school I got my first job at a garden center where I learned to garden and landscape. I've been growing plants from seed and designing native plant gardens for over six years. I hope to share some of my knowledge with you! Additionally I am a wood worker / DIY enthusiast. I enjoy designing/building projects (with hand tools when I can!). I hope to give you some tips and useful information!

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