Petunia hybrida – A Comprehensive Guide to Growing and Caring for Hybrid Petunias

The Petunia hybrida, commonly known as Hybrid Petunia, is an annual herbaceous plant belonging to the Solanaceae family. This hybrid species can grow up to 60 centimeters tall, with stems that sprawl on the ground and are covered in a layer of sticky, soft trichomes.

The leaves are ovate with a tapering tip and have short petioles or are sometimes nearly sessile. Flowers emerge singly from the leaf axils. Their corolla can be white or pansy purple with various streaks and is funnel-shaped. The fruit is a conical capsule, and the seeds are nearly spherical and brownish. The flowering period extends from April to November.

Native to South America, the Hybrid Petunia thrives in warm, sunlit environments. It’s a long-day plant requiring ample sunlight for optimal growth and flowering. Under conditions of low temperatures and limited sunlight, while vegetative growth may be abundant, flowering is inhibited. The primary propagation methods include seed sowing, stem cuttings, and tissue culture.

Hybrid Petunias are valued for their vibrant colors and visual appeal, making them a popular choice for urban floral displays. The flowers symbolize “peace of mind” in the language of flowers.

Morphological Characteristics

This annual herbaceous hybrid species typically grows 30-60 centimeters tall and is entirely covered with glandular trichomes. The sprawling stems are coated with a layer of sticky, soft hairs.

The leaves have short petioles or are nearly sessile, with an ovate shape, acute apex, and a broad cuneate or cuneate base. The leaf margins are entire, measuring 3-8 centimeters in length and 1.5-4.5 centimeters in width. The lateral veins are inconspicuous, with 5-7 pairs per leaf.

Solitary flowers emerge from the leaf axils on 3-5 centimeter long pedicels. The calyx is deeply 5-lobed, with linear lobes about 1-1.5 centimeters long and roughly 3.5 millimeters wide, obtuse at the tip and persistent in fruit.

The corolla can be white or pansy purple with various streaks. It is funnel-shaped, 5-7 centimeters long with an expanding tube and a spreading, pleated limb that is shallowly 5-lobed. The androecium consists of 4 long stamens and 1 short stamen, with the style slightly exceeding the stamens in length.

The fruit is a conical capsule, approximately 1 centimeter long, bisected, with each section slightly dehiscent at the apex. The seeds are minute, nearly spherical, with a diameter of about 0.5 millimeters and are brownish in color.

Growth Environment

As a long-day plant, Hybrid Petunias require ample sunlight during their growth period. The optimal temperature range for growth is between 13°C to 18°C. During winter, temperatures should be maintained between 4-10°C; growth ceases below 4°C. They can tolerate temperatures above 35°C during summer.

During peak growth in summer, Hybrid Petunias require adequate water, especially during hot weather. Watering is best done in the early morning or evening to maintain soil moisture. However, excessive rainfall during the rainy season can impede growth.

Prolonged soil saturation can lead to root rot and plant death. Therefore, for container-grown Hybrid Petunias, it’s crucial to use a well-draining, fertile, sandy-loam soil mix.

Propagation Methods

Three primary methods are used for propagating Hybrid Petunias: seed sowing, stem cuttings, and tissue culture.

Seed Sowing: This method is typically performed annually. Sowing time depends on the desired flowering period; for May flowers, seeds are sown in a greenhouse in January, while for October flowers, sowing occurs in July. Petunia seeds are extremely small, with 9,000-10,000 seeds per gram.

The ideal germination temperature is 20-22°C. Seeds are sown indoors in containers using a sterilized mixture of potting soil, leaf mold, and fine sand. The seeds should not be covered with soil, only lightly pressed into the surface. Germination occurs in about 10 days. When true leaves appear, the ambient temperature should be maintained between 13-15°C.

Stem Cutting Propagation: This can be done year-round indoors. After flowering, take 10 cm long cuttings from the growing tips and insert them into a sand-based rooting medium. The substrate temperature should be 20-25°C. Roots typically form in 15-20 days, and the cuttings can be potted after 30 days.

Tissue Culture Propagation: Explants can be seeds, leaf segments, or fertilized ovules. For seeds, surface sterilization involves soaking in detergent solution for 5 minutes, followed by thorough rinsing. Seeds are then sterilized by soaking in 75% ethanol for 8 minutes, followed by 0.1% mercuric chloride solution for 7 minutes.

After rinsing with sterile water, the seeds are cultured on MS medium supplemented with 6-benzylaminopurine (0.5-1.0 mg/L) and naphthaleneacetic acid (0.1 mg/L). Shoots appear after 15 days. These shoots are subcultured, and after 20 days, one shoot can produce more than 10 new shoots.

Robust 1 cm shoots are transferred to 1/2 strength MS medium containing 0.05-0.20 mg/L naphthaleneacetic acid. Within 10 days, 100% of the shoots develop roots, forming complete plantlets.

Cultivation Techniques

Moisture Management

Watering should follow the principle of “water thoroughly when dry, but avoid overwatering.” Petunias prefer slightly dry soil conditions. After flowering begins, ensure sufficient watering, as dry soil can lead to premature wilting.

Fertilization

During early seedling growth, apply diluted fertilizer frequently. Use a fertilizer high in nitrogen and potassium but relatively low in phosphorus. If excessive vegetative growth occurs, apply a calcium and magnesium compound fertilizer at concentrations of 0.1%-0.2%.

During the peak growth period, apply diluted liquid fertilizer every 7 days. Petunias have higher requirements for boron and calcium. If leaves show interveinal chlorosis, it’s often due to boron or calcium deficiency. Apply boron (40-60 mg/kg) or calcium compound fertilizer as a corrective measure.

Light Regulation

Petunias are heliophytes, requiring ample sunlight for optimal growth and flowering. Judicious shading can enhance flower size, color intensity, and prolong the blooming period.

Flowering Control

Pruning is crucial for managing the flowering time of petunias. After the plant has established its basic structure, pinching the growing tips can delay flowering.

Provide support to prevent flower stems from lodging during peak bloom. After the main flowering period, prune the stems, leaving 2-3 cm at the base of each branch to encourage new branching and subsequent flowering.

Main Value

Medicinal Value

Petunia seeds have been traditionally used to promote qi circulation and as an anthelmintic.

Medicinal Part: Seeds.

Uses: For ascites, abdominal distension, constipation, and intestinal parasites. The recommended dosage is 6-9 grams.

Ornamental Value

Hybrid Petunias produce large flowers with a rich color palette and diverse forms. Colors range from white, pink, red, purple, and blue to even black, as well as various spotted and edged varieties.

Their vibrant colors and impressive visual impact have earned them the moniker “queen of flower beds,” making them a popular choice for urban landscaping and ornamental horticulture.

Cultural Significance

In the language of flowers, the petunia symbolizes “peace of mind,” adding a layer of meaning to its ornamental value in gardens and floral arrangements.