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How to Grow and Take Care of Petunias

A botany graduate, Nithya Venkat enjoys writing about plants that sustain life on Earth.

This guide will provide you with all the basic information you need to grow wonderful petunias.

This guide will provide you with all the basic information you need to grow wonderful petunias.

Bright, Colorful Flowers With Long Blooming Periods

The petunia plant belongs to the Solanaceae family native to South America. They are well known for their bright, colorful flowers and the long-blooming period that lasts from spring until frost. They are easy to grow both in containers and gardens.

These plants are herbaceous annuals that grow well in average, medium moisture, well-draining soil in full sun to light shade. They can tolerate poor soil as long as the drainage is good with bright sunlight.

There are many petunia hybrid varieties with varying colors and plant sizes. Most commercially sold petunias are complex hybrids, a cross between Petunia axillaris and Petunia integrifolia. These plants can be planted in beds, borders, edging, or ground cover. They can also be grown in containers, window boxes, and hanging baskets.

The genus name “petunia” comes from the Latinized form of the Brazilian name "petun" for tobacco, to which these plants are closely related.

Petunia Flowers - Mix of white and purple

Petunia Flowers - Mix of white and purple

Basic Information About Petunias

Petunia hybrids are generally bushy and can spread in their habit with varying sizes depending on the variety. The leaves are sessile (lacking a petiole) and are usually oval shaped with smooth margins. The flowers are funnel shaped with five fused or partially fused petals and five green sepals.

Most species are insect pollinated, except for Petunia exserta, which is pollinated by hummingbirds. The minute seeds are borne in a dry capsule.

Although the petunia is basically a perennial, the common garden petunia is most often grown as an annual with a long blooming period from early summer until frost.

The flowers bloom in many colors. They can be speckled or veined in contrasting colors and can feature single or double flowers.

Pink Petunia Flowers

Pink Petunia Flowers

How to Grow and Take Care of Petunias

The easy way to grow petunias is to buy healthy young plants from the nursery. If you are growing from seeds, start the seeds indoors 8–10 weeks before the last spring frost date in your area, and plant the young petunias outdoors after the later spring frost date.

Petunias need full sun or they will become spindly. These plants grow well in different soil types as long as the soil is well-draining and moderately fertile with five to six hours of exposure to bright sunlight.

Many varieties will thrive even if the soil is not rich. They do not require frequent watering—except for the “spreading” type of petunias, which need regular watering.

In shaded locations, petunias produce fewer flowers. Deadheading helps to prolong blooming and keeps the plants looking healthy and well-groomed.

Planting

Petunia seeds are tiny and dust-like and need bright sunlight to germinate.

When the plants have sprouted three leaves, plant them outside with a space of 1 foot apart.

If you are planting petunias in containers, use a potting mix that will drain well.

Care Instructions

Petunias are heat tolerant and do not need frequent watering. Water the petunias once a week. Avoid shallow watering, as this will encourage shallow roots. The spreading type of petunias grown in containers will need more frequent watering than those planted in the ground.

Fertilize petunias monthly with a balanced fertilizer for ideal growth and blooms. By mid-summer, most petunias tend to get leggy, producing blossoms at the tips of the long, leafless stems. To keep the petunias tidy and sprouting many flowers, prune the shoots back to about half their length.

Petunia Groups

Petunias are divided into the following groups based on flower size:

  1. Multiflora petunias are long-lasting and fast growers. They have smaller but more abundant flowers and are great for summer bedding or in a mixed border.
  2. Grandiflora petunias are the most popular type and produce large flowers that are 3–4 inches across. The flowers can bloom as singles or ruffled doubles, and some can have a pendulous or cascading habit that makes them more suitable for hanging baskets and window boxes.
  3. Floribunda petunias range between the grandiflora and multiflora groups in size and are free-flowering like the multiflora varieties and produce medium-sized blooms.
  4. Milliflora petunias are compact, miniature plants that produce an abundance of miniature flowers that are an 1–1.5 inches in diameter. These flowers are prolific growers and last all season. They are good as edging plants.
  5. Spreading or Trailing petunias are low-growing and can spread as much as 3–4 feet. They form a beautiful, vibrant splash of ground cover, because the flowers form along the entire length of each stem. They can be planted in window boxes or hanging baskets.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Nithya Venkat