Petunia

( pet - YEW - nee - uh )

At-A-Glance Information

Petunias are a classic garden favorite, and need full sun and regular water. Their blooms will attract butterflies to your garden and can be either single, semi-double or double flowering. They come in all colors except green, and can be bicolored or Picotee. They are wonderful in containers and hanging baskets, where their trailing stems can take center stage. There are many different varieties and species, all widely available for purchase at nurseries and larger stores.

Petunia species and Varietals

The genus Petunia includes 20 species and hybrids, and is a member of the plant family Solanaceae. Petunias grow in all zones (To find your zone, click here: Zone Map).

Petunia x atkinsiana (Petunia x hybrida) (Hybrid Petunia, Garden Petunia
The plants in this hybrid group of Petunia plants are crosses between Petunia axillaris and Petunia integrifolia. Most of the petunias seen in nurseries are this type. There are many different cultivars in this group, outlined below:

Ultra Blue Star
With white and violet blooms.

Blue Frost
Magenta to violet petals with white banding on their edges.

Red Pirouette
Double blooming variety with red and white flowers.

Bravo Salmon Veined
This species produces cream-colored blooms with pink to salmon veining.

Sweet Sunshine Dark Violet
With dark violet blooms.

Blue Daddy
Lavender flowers with purple shading and venation.

Hula Hoop Red
With red flowers that have white banding on the outer edge.

Sugar
Pink flowers with darker pink blushing and venation.

Petunia axillaris (Large White Petunia, Wild White Petunia, White Moon Petunia, Night-Scented Petunia)
These plants are native to temperate areas of South America, and produce the only white flowers in the genus. This is a parent species to the hybrid common Garden Petunia (Petunia x atkinsiana). Leaves are green. Plants typically reach between 1.5 and 2 feet tall and wide.

Petunia exserta (Red Petunia, Brazilian Red Petunia)
These plants are native to a small area in southern Brazil, and is threatened due to habitat destruction as well as the fact that it readily hybridizes with other Petunia species in its range. Flowers are bright red, and have protruding stamens and stigmas. Plants are upright with erect flowering stems.

Petunia integrifolia (Violet Petunia, Violetflower Petunia, Shanin)
These plants are native to Argentina, and bear flowers that are about 1.5 inches in diameter. Individual plants reach up to between 1.5 and 2 feet tall and just as wide when mature and in bloom. Plants in this species are used as a hallucinogenic in Ecuador.

Caring for Petunia

Petunias are best planted in springtime, after the soil has warmed up to at least 60 degrees Fahrenheit. They can be grown from seed, either direct-sown into the garden soil or grown indoors and then planted out. Make sure the danger of frost has passed by before planting. Make sure to leave enough space between your Petunia and other plants; these are vigorous growers and will often choke out other smaller plants. On average, a good spacing is between 12 and 18 inches. Compact varieties can be spaced 4 to 6 inches apart. Plant Petunias in full sun; ideally, these plants like to get between 6 and 8 hours of direct sun for best performance. In warm climates, some afternoon shade is appreciated. Ensure that soil is well-draining, moderately fertile, and has a pH of between 6.0 and 7.0 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a thick layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and increase soil moisture retention.

Water new plantings regularly to help them establish a strong root system in their new home. At maturity, Petunias appreciate moist substrate, and are not able to handle long periods of drought. Ensure that these plants are not getting over-watered, however, as they are also susceptible to developing root rot and other fungal issues. Water at the base of plants. As a general rule of thumb, irrigate whenever the top inch or two of soil feels dry to the touch. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. Pruning is simple for Petunia plants; simply remove any dead, damaged, or diseased foliage at any time, and cut back any leggy growth to encourage a bushier habit. Petunias are typically pulled after the growing season finishes each year and replaced the following spring. However, in mild-winter climates that do not experience frost, they can be considered perennial plants, and be cultivated year after year.

Propagation

Petunia plants can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Petunia, follow the instructions below:

Propagating Petunia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In fall before the first frost of your area, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Avoid taking cuttings from stems that are woody. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new plant.

Propagating Petunia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. The seed pods are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
About 10 to 12 weeks before the last frost of your area, water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-10 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the spring (after the danger of frost has passed), when you can transplant it to its new home.