How to Grow Petunias Organically

Ready to add a splash of color and a hint of nostalgia to your garden? Dive into the world of petunias, those delightful blooms that promise vibrant hues and sweet scents! Whether you’re a seasoned gardener or just starting out, this guide has got you covered with tips on growing these beauties from seed, keeping them healthy, and even bringing back some fragrant heirloom varieties. Let’s dig in and bloom together!

An old-fashioned flower favorite! Home gardeners are growing petunias from seed for their dazzling colors and abundant blooms that continue from early spring until frost. Available in hundreds of varieties, they are one of the most popular flowering annuals and are well suited for use in borders, baskets and containers.

Native to South America, the first petunia specimen (Petunia multiflora) was discovered at the mouth of the Rio de la Plata and was white in color. The original plants were hardy, had trailing 2-3 inch stems and incredible scents. These scents have been lost in many of the modern-day hybrid varieties. Fortunately, many of the old fashioned heirloom varieties are still available to fill the air with their amazing fragrance. A self-seeding annual — 10 to 18 inches tall — that may volunteer in your garden the following season.

Fun fact: There are 35-40 species in the Petunia genus which belong to the nightshade family (Solanaceae) including tomatoes, potatoes and tobacco.

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Petunia Seeds

Old-fashioned varieties are particularly fragrant. Perfect for containers and baskets.

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The beautiful, soft-petaled, many-colored heirloom petunia is a flower straight from our childhood. Planting instructions are included with each seed packet and shipping is FREE!

Quick Guide: Planting, Growing & Caring for Petunias

Very easy to grow in a dizzying range of colors
Choose seedlings or start from seed 8-10 weeks before last frost
Choose a site in full sun with amended soil or in quality potting soil
Plant or hang outside after danger of frost has passed
Pests and diseases are not common, but aphids, flea beetles and slugs may attack stressed plants

Sunlight: Full sun to partial shade
Maturity: 55-75 days from seed to flower
Height: 10 to 18 inches
Spacing: 8 to 18 inches apart in all directions

Site Preparation

Petunia flowers require full sunlight to thrive, but will tolerate some shade. The more shade they receive, the fewer blossoms they will produce.

Soil should be average to rich and well-drained. Prior to planting, work a shovelful or two of organic matter, such as compost or well-aged manure, into the soil (watch our video Flower Gardening from the Ground Up). This helps condition the soil, which improves drainage and will also increase the ability of lighter soils to hold water and nutrients.

How to Plant

Petunias grow easily from seed, but are slow to germinate. Start seeds indoors in pots, 8 to 10 weeks prior to last frost, and sow on the surface of the planting media, do NOT cover (see Starting Annual Flowers Indoors to learn more). Before transplanting into the garden, harden the tender seedlings off to acclimate them to outdoor conditions. At first leave them out only a few hours a day and make sure the soil they’re in doesn’t dry out. Gradually increase the time the plants stay out. After a week (or more) they should be ready.

For good ground cover, space plants 12-18 inches apart. Fertilize monthly with a liquid organic fertilizer to promote healthy growth and remove spent flowers on a regular basis to extend the blooming period.

Insect & Disease Problems

Plants do not have many insect or disease problems. Watch for aphids, flea beetles and slugs, which can occasionally attack petunias, and take the following common sense, least-toxic approach, if found:

Remove weeds and other garden debris to eliminate alternate hosts.
Discard severely infested plants by securely bagging and putting in the trash.
Release commercially available beneficial insects to attack and destroy insect pests.
Spot treat pest problem areas with diatomaceous earth and neem oil.
Scatter Sluggo®, an organic iron phosphate bait, around plants to kill slugs.

To prevent or reduce plant diseases, many of which are characterized by wilting, spots and rotted tissue, we recommend the following:

Avoid overhead watering whenever possible (use soaker hoses or drip irrigation)
Properly space plants to improve air circulation
Apply copper spray or sulfur dust to prevent further infection

Seed Saving Instructions

Petunia plants are self-seeding. You can save the seed if you’re interested, but the flowers won’t always come true to type. They usually revert to a mix of small white, lavender and rose flowers.