How to Grow and Care Galaxy Petunia: Easy Tips

If you’re in search of a stunning flower that creates a breathtaking display in various settings such as containers, hanging baskets with trailing tendrils, or as an attention-grabbing bedding plant, then the galaxy petunia is the perfect choice.

This unique petunia, also known as the night sky petunia, was developed by an Italian plant breeder who successfully crossed two different petunia varieties. How to grow and care Galaxy Petunia; Its remarkable beauty led to the plant receiving the esteemed Fleurostar award for being the ‘Winner with the Wow Factor’ upon its commercial release in 2016.

How to grow and care Galaxy Petunia; the purple trumpet-shaped flowers of the galaxy petunia are adorned with white spots scattered across them, giving them a mesmerizing appearance reminiscent of the vast cosmos. How to grow and care Galaxy Petunia; Although it’s unfortunate that these fast-growing plants typically only survive for one growing season, their flowers endure until late fall when the initial frosts arrive. To cultivate galaxy petunias, it is recommended to plant them in the spring, once temperatures have risen above 65 degrees Fahrenheit.

How to Grow and Care Galaxy Petunia

How to grow and care Galaxy Petunia; It’s important to note that the blooming pattern of galaxy petunias is heavily influenced by the temperatures in their surroundings. In hot weather conditions, the plants may not exhibit the distinctive white spots that contribute to their impressive visual effect. How to grow and care Galaxy Petunia; Therefore, it might be necessary to wait until cooler nights arrive, closer to the end of summer, before they once again resemble a starry cosmos.

Common Name:  Galaxy Petunia, Starry Sky Petunia

Botanical Name:  Petunia ‘Night Sky’

Family:  Solanaceae

Plant Type:  Perennial, Herbaceous

Soil Type:  Well-drained

Soil pH:  Neutral, acidic

Bloom Time:  Summer, fall

Flower Color:  Purple, white

Mature Size:  14-16 in. tall, 24-36 in. wide

Sun Exposure:  Full

Hardiness Zones:  9-11 (USDA)

Native Area:  Cultivar, no native range

How to Grow and Care Galaxy Petunia

Galaxy Petunia Care

Although petunias have the potential to be perennials in suitable climates, they are commonly cultivated as annual flowers, completing their lifecycle within a single growing season. These flowers reach maturity rapidly and exhibit a prolonged period of blooming. While achieving the flourishing white spots on these plants can be challenging, even when they remain solid purple, they still serve as a lovely addition to any garden.

Galaxy petunias, when positioned in a sunny location, demand minimal maintenance. Furthermore, their resilience to urban pollution is an added advantage, making them an excellent option for gardeners in city environments.


While the galaxy petunia is generally low-maintenance, it does necessitate ample sunlight. Insufficient exposure to the sun can result in reduced flower production and compromised health for these plants, often leading to stem stretch.


When it comes to soil preferences, your galaxy petunia is not overly particular. However, it is crucial to choose soil with excellent drainage as standing water is not well-tolerated by these plants. They prefer consistent moisture levels.

Ideally, opt for soil that is rich in organic matter. Given their extended blooming season, galaxy petunias require substantial energy, and fertile soil will provide the necessary nutrients for their optimal growth and development.

How to Grow and Care Galaxy Petunia


While the galaxy petunia dislikes prolonged dryness, excessive watering can pose a problem. Overwatering can lead to weakened stems and hinder the proper growth of flowers, especially if the plants have “wet feet” due to standing water. Typically water your galaxy petunia once a week during the warm months is adequate.

If your galaxy petunias are cultivated in hanging baskets or containers, they will require more frequent watering compared to those planted in the ground—sometimes even daily during the hot summer months. A general guideline is to water these plants when the top 5 to 6 inches of soil feel dry to the touch. Once the soil has dried, it is advisable to provide a deep watering of 1 to 2 inches of water.

How to Grow and Care Galaxy Petunia

Climate and Moisture Level

The captivating pattern displayed by the galaxy petunia is significantly influenced by temperature. Higher temperatures during the summer have been observed to lead to fewer white spots on the flowers. It is probable that the patterns on your flowers will evolve as the season progresses.

In the peak of the hot season, when nighttime temperatures remain high, your flowers may exhibit a uniform purple color. However, as the nights gradually become milder, creating a contrast with the daytime weather, you can expect the spotted appearance to reemerge on your plant’s flowers.


To ensure the continuous blooming of your galaxy petunia, it is advantageous to provide regular fertilization throughout its growing season, especially if the soil lacks richness. When cultivating these plants in hanging baskets or containers, feeding them with a balanced, slow-release fertilizer every other week should meet their nutritional requirements adequately. On the other hand, if they are planted in the ground as bedding plants, fertilizing once every three to four weeks will likely suffice. It is advisable to consult the instructions on the product label for the recommended amount of fertilizer to use.

How to Grow and Care Galaxy Petunia

Types of Galaxy Petunias

Although galaxy petunias are already a unique cultivar, there are two more variations of this flower that you might consider growing either in containers or in your garden:

‘Starry Sky Burgundy’: This particular variety showcases a deep red base color with white speckled “stars,” and it also exhibits a solid yellow star shape at the center of each flower.

How to Grow and Care Galaxy Petunia

‘Pink Sky’: Unlike the other varieties, this pink version of the night sky petunia does not feature shapes at the centers of its flowers. However, it compensates with a vibrant hot pink backdrop adorned with white speckles.

How to Grow and Care Galaxy Petunia

How to Prune

Similar to other petunia varieties, your galaxy petunias will thrive when subjected to regular pruning or deadheading, promoting new flower growth. Simply trim away any wilted or dying flowers, as well as leggy stems. By doing so, not only will you encourage the production of more flowers, but you will also aid in the plant’s overall fuller growth.

How to Grow and Care Galaxy Petunia

How to Propagate

To propagate your galaxy petunia and create new plants, summer is the ideal time to take cuttings as part of the pruning process. However, it is important to avoid using the plant growth regulator B-Nine during propagation, as it has been known to cause the flowers to turn white. Here are the steps to follow:

Step 1: Prepare a container with a well-drained soil mixture consisting of peat moss and sand. Ensure that the soil is moist but not overly saturated.

Step 2: Select a healthy stem from your galaxy petunia plant that is at least 4 inches long. Remove any leaves except for those at the top.

Step 3: Dip the cut end of the stem into a powdered rooting hormone and carefully plant it in the moistened growing medium. Gently press the soil around the stem.

Step 4: Place the container with the new cuttings in a cool area where they can receive indirect sunlight. Allow several weeks for the roots to develop.

 Step 5: After approximately three to four weeks, lightly tug on the plants to check if the roots have established beneath the soil’s surface. At this stage, pinching the plants is recommended to enhance growth. Your rooted plant should now be ready for transplanting.

How to Grow and Care Galaxy Petunia

How to Grow From Seeds

Galaxy petunia seeds are available for home cultivation through select commercial nurseries. It is essential to choose a reputable supplier to ensure the authenticity of the hybrid. However, be prepared for a challenging process. These minuscule seeds can take up to twelve weeks to germinate and require ample sunlight with a light soil covering. Here’s a step-by-step guide on growing galaxy petunias from seeds:

Step 1: Prepare seed-starting containers with well-draining soil that is moist.

Step 2: Plant the galaxy petunia seeds just slightly below the surface of the soil.

Step 3: Position the containers in a cool area that receives abundant bright, indirect light or full sun. Maintain consistent moisture in the soil.

Step 4: If the external weather is already warm, consider keeping the plants indoors in an air-conditioned room adjacent to a well-lit window. Germinating the seeds in cooler weather conditions will enhance the distinct white speckles characteristic of this cultivar.

Step 5: Once the seedlings have germinated, transplant them into larger containers and provide regular care as usual.

How to Grow and Care Galaxy Petunia

Potting and Repotting

When young petunias start to outgrow their pots or if petunias are in containers that are too large, repotting becomes necessary to prevent issues like root rot. The good news is that repotting your galaxy petunias for either reason is a straightforward process.

In the spring, at the onset of the growing season, repot your petunias. Select a container that provides a few inches of space around the root cluster of your plant, avoiding excessively large containers. Opt for unglazed ceramic or terracotta pots as they offer optimal drainage. It is crucial to ensure that the container for your galaxy petunia has drainage holes at the bottom.

Carefully remove your petunias, including the entire root ball, from their previous container. Gently shake off any excess soil from the roots, and then transplant them into the new pot. Keep the soil moist by watering it, and apply a fertilizer boost to kickstart the growing season.

How to Grow and Care Galaxy Petunia


Unless you reside in a tropical region, galaxy petunias cannot survive outdoors. However, they can be preserved as perennials by overwintering them indoors. When temperatures start to decline in the autumn, approximately reaching around 40 degrees Fahrenheit, it is advisable to bring your plants inside. Position them near a south-facing window to maximize exposure to natural light. Alternatively, using a plant grow light to simulate full sun is an excellent choice to ensure their survival until spring. Apart from this adjustment, continue caring for the plants as you would normally do.

Common Pests & Plant Diseases

Similar to other petunias, your galaxy petunia plant is vulnerable to several common garden pests such as aphids, whiteflies, and slugs. However, there is a simple homemade solution to keep these pests at bay. Just combine 1 to 2 tablespoons of liquid dish soap with 1 gallon of water, and use this mixture to spray your plants.

Additionally, galaxy petunias are prone to developing Botrytis, a fungal disease commonly known as gray mold. This condition often arises from overwatering. To prevent Botrytis, ensure that your petunias’ containers have sufficient drainage holes, allowing excess water to escape. It is also advisable to wait until the top layer of the soil begins to dry out before watering again. By practicing these precautions, you can minimize the risk of fungal growth and promote healthier plants.

How to Grow and Care Galaxy Petunia

How to Get Bloom

The blooming period of galaxy petunias begins in spring, and these visually appealing flowers persist until the arrival of fall. To prolong their flowering season, it is beneficial to bring your plants indoors before the first frost of autumn.

If your galaxy petunias are not producing blooms, insufficient sunlight could be the underlying issue. It is crucial to expose these plants to full sun, providing them with a minimum of six hours of sunlight per day to promote vibrant and healthy blooms. Additionally, regular applications of fertilizer can significantly contribute to the flowering process. Once your galaxy petunias have bloomed, it is essential to deadhead the flowers to encourage new growth to continue.

Common Problems

Caring for galaxy petunias is generally uncomplicated; however, when cultivating them in a garden, it is possible to encounter a few common challenges. The key to keeping your petunias healthy lies in maintaining a proper watering and fertilizing regimen.

Wilted Leaves

Improper watering can result in wilted leaves for galaxy petunias, whether due to overwatering or underwatering. To determine the moisture level of your plant’s soil, examine the top few inches. If the soil is dry, it indicates the need for more frequent watering. Conversely, if the soil is overly wet, it is crucial to allow the plants to dry out.

How to Grow and Care Galaxy Petunia

Brown Leaves

When brown leaves appear on your galaxy petunias, it is a clear indication that your plants are not receiving adequate water. While it is crucial to avoid overwatering this species, it is recommended to provide 1 to 2 inches of water when the soil starts to dry out.

How to Grow and Care Galaxy Petunia

Yellow Leaves

If your galaxy petunias have yellowed leaves, it could be an indication that they are not receiving sufficient sunlight. However, it is also possible that they require more fertilizer. For optimal growth, petunias thrive when fertilized consistently, typically every other week during the growing season.

How to Grow and Care Galaxy Petunia