How to Grow and Care for Galaxy Petunia

A real flower that looks like a speckled night sky

Galaxy petunias

The Spruce / Kara Riley

If you're looking for a showstopping flower that looks spectacular in containers, cascading over the sides of hanging baskets, or being used as an eye-catching bedding plant, look no further than the galaxy petunia.

Also called night sky petunia, this new species was created by an Italian plant breeder who crossed two other petunia varieties. It's no surprise the plant won the prestigious Fleurostar award for 'Winner with the Wow Factor' when it was released commercially in 2016.

The galaxy petunia's purple trumpet-shaped flowers have white spots dotted across them that create an other-worldly look reminiscent of the cosmos. It's a shame that these fast-growing plants typically only last one growing season, but once they're in bloom, the flowers remain until the late fall when the first frosts hit. Plant galaxy petunias in the spring after temperatures are above 65 degrees Fahrenheit.

It's worth noting that the temperatures of their environment heavily influence the blooming pattern of galaxy petunias. If the weather is too hot, the plants might not display the white spots that give them an impressive appearance. You may have to wait for cooler nights (closer to the end of the summer) before they start to resemble a starry cosmos again.

Common Name Galaxy Petunia, Starry Sky Petunia
Botanical Name Petunia 'Night Sky'
Family Solanaceae
Plant Type Perennial, Herbaceous
Mature Size 14-16 in. tall, 24-36 in. wide
Sun Exposure Full
Soil Type Well-drained
Soil pH Neutral, acidic
Bloom Time Summer, fall
Flower Color Purple, white
Hardiness Zones 9-11 (USDA)
Native Area Cultivar, no native range

Galaxy Petunia Care

While petunias are perennials in the right climate, they're typically grown as annual flowers that have one full growing season. They mature quickly and have a long bloom period. It can be tricky to get the white spots to flourish on these plants, but even when they're just solid purple, they'll make a nice addition to your garden.

If they have a sunny position, your galaxy petunias won't require much maintenance. It's also a bonus that they aren't fazed by urban pollution, making them a great choice for city gardeners.

purple galaxy petunias
The Spruce / Kara Riley 
side view of galaxy petunia
The Spruce / Kara Riley 
frontal view of galaxy petunia
The Spruce / Kara Riley 
new galaxy petunia growth
The Spruce / Kara Riley 
front view of a galaxy petunia
The Spruce / Kara Riley 


Although this plant is easy to grow, the galaxy petunia does require full sun. If they have too much shade, these plants won't produce so many flowers, and they won't be as healthy (often suffering from stem stretch).


Your galaxy petunia isn't a fussy plant when it comes to soil types. The main requirement is that you select one with good drainage. It won't tolerate standing water and prefers even moisture.

Ideally, you want a soil that is also rich in organic matter. Their long blooming season means galaxy petunias use a lot of energy, and fertile soil will supply them with the nutrients they need to flourish.


Although they don't like to be dry for long periods, overwatering is a problem for the galaxy petunia. Too much water can weaken your plant's stems, and the flowers won't grow well with wet feet from standing water. Weekly watering in the warm months is usually sufficient.

If your galaxy petunias are growing in hanging baskets or containers, they'll need more frequent watering than those grown in the ground—even daily in the hot summer months. It's generally recommended to water these plants when the top 5 to 6 inches of soil are dry to the touch. Once dry, water deeply with 1 to 2 inches of water.

Temperature and Humidity

Temperatures can have a big impact on the striking pattern that the galaxy petunia is known for. Warmer summer temperatures have been shown to result in fewer white spots. You'll likely find that the patterns on your flowers will change throughout as the season progresses.

During the hottest part of the season, your flowers may be a solid purple color when temperatures remain high at night. As night temperatures become milder and contrast the daytime weather, your plant's flowers should begin to appear spotted again.


Your long-blooming galaxy petunia will benefit from regular fertilization throughout its growing season, particularly if the soil it's planted in isn't particularly rich. If these plants are kept in hanging baskets or containers, feeding them a balanced, slow-release fertilizer every other week should be sufficient. For those grown in the ground as bedding plants, fertilizing once every three to four weeks will likely be enough. For the amount of fertilizer to use, follow the instructions on the product label.

Types of Galaxy Petunias

While galaxy petunias are a cultivar themselves, there are two additional varieties of this flower that you may seek to grow in containers or your garden:

  • 'Starry Sky Burgundy': This variety offers a dark red background to its white speckled "stars," and it also features a solid yellow star shape at the center of the flower.
  • 'Pink Sky': This pink variety of night sky petunias doesn't have shapes in the centers of its flowers, but it has a hot pink background for its white speckles.


Like other types of petunias, your galaxy petunias will do best with regular pruning or deadheading to encourage new flower growth. Simply prune away any dead or dying flowers and leggy stems. Along with producing more flowers, this will also help your plant grow fuller.

Propagating Galaxy Petunia

Propagate your galaxy petunia in the summer when you take cuttings to prune the plant. Steer clear of B-Nine if you use a plant growth regulator during propagation, as this has been shown to turn the flowers white. Taking cuttings will help keep your petunias growing healthy, and they can also be used to grow new plants. Here's how:

  • Step 1: Prepare a container for your cuttings with a well-drained soil medium mixed with peat moss and sand. Water until it is moist, but not saturated.
  • Step 2: Trim a healthy stem at least 4 inches long from your galaxy petunia plant and remove all but the top leaves.
  • Step 3: Dip the cut end in a powdered rooting hormone and plant your cutting in the moistened growing medium. Press the soil down around it gently.
  • Step 4: Place your new plants in a cool area with indirect sunlight for several weeks to allow their roots to grow.
  • Step 5: Lightly tug on the plants to determine whether their roots have taken hold under the soil's surface. After around three to four weeks, pinching is recommended to improve growth, and your rooted plant should be ready for transplanting.

How to Grow Galaxy Petunia From Seeds

Some commercial nurseries sell galaxy petunia seeds that can be grown at home. Always opt for a reputable supplier to ensure you're getting the right hybrid, and be prepared for a challenge. These tiny seeds can take up to twelve weeks to germinate, and they need plenty of sunlight with only a light covering of soil. Here's how to grow galaxy petunias from seeds:

  • Step 1: Prepare seed-starting containers with moist, well-draining soil.
  • Step 2: Plant your galaxy petunia seeds just barely below the soil's surface.
  • Step 3: Place the plants in a cool area with plenty of bright, indirect light or full sun. Continue keeping the soil consistently moist.
  • Step 4: If the weather outside is already getting hot, keep the plants in an air-conditioned room next to a bright window. This cultivar's signature white speckles will be the most prominent when germinated in cool weather.
  • Step 5: Once your seedlings germinate, pot them up in larger containers and care for them as usual.

Potting and Repotting Galaxy Petunias

Young petunias should be repotted when they begin to overtake the pot, while petunias in containers that are too large may be more susceptible to developing root rot. Thankfully, repotting your galaxy petunias for either reason is a simple process.

Repot petunias in the spring when the growing season begins. Choose a container that leaves a few inches of soil around your plant's root cluster (avoid oversized containers). Pots made from unglazed ceramic or terracotta are best to allow for plenty of drainage. Always ensure your galaxy petunia's container has drainage holes on the bottom.

Gently remove your petunias, including the entire root ball, from their previous container. Shake off excess soil from the roots, then transplant them into the new pot. Water the soil to keep it moist and add a boost of fertilizer to begin the growing season.


While they won't survive outside unless you live in a tropical region, galaxy petunias can be overwintered as perennials indoors. Once temperatures begin dropping in the fall (nearing 40 degrees Fahrenheit), bring your plants inside and place them as close to a south-facing window as possible. Using a plant grow light to simulate full sun is a great option to help prevent them from dying off before spring. Otherwise, care for the plants as usual.

Common Pests & Plant Diseases

Like other petunias, your galaxy petunia plant is susceptible to a few common garden pests like aphids, whiteflies, and slugs. Thankfully, you can keep pests off your plants with a homemade solution. Simply mix 1 to 2 tablespoons of liquid dish soap in 1 gallon of water, then spray the plants down.

Galaxy petunias are also prone to developing Botrytis (a gray mold fungal disease) when overwatered. Always ensure that your petunias have plenty of drainage holes in their containers, and allow the top of the soil to begin drying out before watering.

How to Get Galaxy Petunia to Bloom

Galaxy petunias bloom in the spring, and these attractive flowers continue to bloom until fall. Bringing your plants indoors before the first frost of fall is a great way to extend their flowering season.

If your plants aren't blooming, they may not be receiving enough sunlight. It's important to expose these plants to full sun—at least six hours per day—to encourage healthy blooms. Adding regular boosts of fertilizer is another component that can help your plants flower. Once your galaxy petunias bloom, deadheading the flowers is essential for new growth to continue.

Common Problems With Galaxy Petunia

Galaxy petunias are fairly easy to care for, but especially when growing them in the garden, it's possible to run into a few common issues. Most importantly, maintaining a healthy watering and fertilizing schedule can keep your petunias healthy.

Wilted Leaves

Galaxy petunias can have wilted leaves due to improper watering, whether too much or too little. Check the top few inches of your plant's soil to see if it's moist. Dry soil means it's time to begin watering more often, while overly wet soil is a sign that your plants need to dry out.

Brown Leaves

Brown leaves on your galaxy petunias indicate that your plants aren't receiving enough water. While you should always avoid overwatering this species, it's best to provide 1 to 2 inches of water when the soil begins to dry out.

Yellow Leaves

Yellowed leaves may be a sign that your galaxy petunias aren't receiving enough sun, but this can also mean they need more fertilizer. Petunias do best when fertilized regularly (about every other week throughout the growing season).

  • How long can galaxy petunias live?

    Since they're not very cold-hardy, galaxy petunias typically die off each year unless overwintered indoors. However, when growing petunias in a hot climate, these plants can live for about three years.

  • What plants are similar to galaxy petunias?

    While galaxy petunias feature very unique patterns, there are flowers with other color varieties that look similar to petunias. Calibrachoa, mandevilla, and geraniums are popular options.

  • Can galaxy petunia grow indoors?

    Galaxy petunias are typically grown outdoors, but they can also be grown inside your home with the right light exposure. Place your petunias near a window that receives full sun for best results.