How to Grow and Care for Galaxy Flowers

By Sabrina Lopez | September 28, 2022

Close up image of the unique purple spotted flowers of Petunia Night Sky, in a natural outdoor setting.

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Jump to: Fast Facts | How to Grow | How to Prune | How to Repot | How to Propagate | Common Issues | Our Recommendation | FAQ

Galaxy flowers bring the dazzling beauty of the starry night sky into your home or garden. These deep purple flowers are sprinkled with brilliant white dots, which earned them the nickname night sky flowers. Gardeners grow these delicate but hardy plants indoors and outdoors across the country. They are easy to start from flower seeds, and they flourish with moderate levels of care and attention.

In fact, the galaxy flower won the prestigious FleuroStar Contest in 2015/2016. Held annually in the Netherlands and Germany, this contest identifies the “winner with the wow factor.” More than one-third of the contest’s 30 judges awarded the petunia night sky the maximum number of points for commercial potential and point-of-sale attractiveness. Today, its unique patterns make this flower popular with botanists and flower lovers around the world.



Courtesy Amazon

Wivolibe Night Sky Petunia Seeds


This set of over 500 seeds will grow into beautiful, elegant galaxy flowers that are the perfect complement to any garden or indoor space. These truly unique flowers release in the summer and can provide a “night sky” look through the fall season. They are drought-tolerant and need only six direct hours of sunlight per day.

$6.99 On Amazon


Fast Facts on Galaxy Flowers

The galaxy flower is a type of petunia—a genus of more than 20 species of flowering perennials that is related to the potato, eggplant, and tobacco plant. Though petunias are native to South America, Italian botanist Antonella Capo first bred the galaxy flower in 2012.

Common nameNight Sky Petunia, Starry Sky Petunia

Plant family


Native climate


Light level

Full, direct sunlight for five to six hours daily

Average mature height

14 to 16 inches tall

Soil type

Well-drained, neutral or slightly acidic

Frequency of watering

Once weekly


Nontoxic to humans and animals

Ideal humidity level


Formally known as the petunia night sky, the galaxy flower grows best in warm, humid climates. The secret to growing petunias is a mix of full sun and well-drained soil. These flowers thrive in five to six hours of direct sunlight per day. You don’t necessarily want your plants to get too hot, however.

Temperature changes affect the white-to-purple ratio on the flowers. In colder temperatures, galaxy flowers show more white, and in hotter environments, they emphasize purple. The white dots will disappear entirely if the weather stays hot enough for long enough. 

Galaxy petunias enjoy a robust growing season that can begin in the spring and extend into the fall. When fully grown, these plants can be 14 inches tall.



How to Grow Galaxy Flowers Indoors

Galaxy flowers feature some of the most beautiful blossoms in the world. They’re also relatively easy to grow, as long as you have the right conditions. To care for your galaxy flowers, water them regularly and fertilize them monthly. Pruning the plants back after they bloom will encourage new growth.


Galaxy flowers need regular fertilization. Gardeners can use a balanced fertilizer at 150 to 250 parts per million (ppm) nitrogen supplemented with iron and minor elements in a constant feed. Your local garden supply shop can help you find and mix the right fertilizer.

If the pH balance in your soil is too acidic (yellowing leaves are a telltale sign of this problem), irrigate your plant with high-alkaline water.


Galaxy flowers need a lot of light. Optimally, these plants would get five to six hours of full sun daily. If they have insufficient sunlight, galaxy flowers fail to thrive—their blossoms thin out, and they show signs of stem stretch.

For best results, place your galaxy flowers near a window with plenty of natural light, or you can DIY your light source by investing in some plant lights. LED lights and other artificial light sources can encourage your petunias to blossom, but gardeners should keep light intensity to 50,000 to 80,000 lux.


Like other petunias, galaxy flowers flourish best in rich, loamy soil filled with organic matter. However, they will grow in nearly any potting mix you put them in. Ask at your local garden center or search on Amazon for a product you like. 

Whatever potting mix you choose, create adequate drainage holes for your plants. If petunias sit in water too long, they can develop root rot. This condition cannot be reversed; if not addressed, it will destroy your plant.


Galaxy flowers like to grow in warm temperatures. The temperature should run between 55 degrees Fahrenheit and 75 degrees Fahrenheit during the day and 55 degrees Fahrenheit to 65 degrees Fahrenheit at night. 

Temperatures dramatically affect the striking colors and patterns that make galaxy flowers unique: the colder the environment, the more white spots on the petal. The deep purple color tends to take over as the temperature warms up. 

When the weather gets hot enough, the flower’s distinctive white speckles may disappear altogether. Not to worry, though; the dark purple petunias are still beautiful in your garden.


Watering is a bit delicate with these plants. The soil should be moist but not too wet. Make sure to water your galaxy flowers frequently, but do not let them sit in water, or they can develop root rot.



How to Prune Galaxy Flowers

Pruning your galaxy flowers is a crucial step in keeping them healthy and ensuring they bloom beautifully. It’s best to prune your plants once in mid-July, again in mid-August, and finally in mid-September. Don’t prune more than one-third of the plant’s stems at any single pruning.

To prune, cut off branches that are browning or dead, as well as any stems with flowers. If you want to encourage new growth, remove any buds inside of the flower that haven’t yet opened. These can be snipped with scissors or pulled off gently with your fingers.



How to Repot Galaxy Flowers

Galaxy flowers enjoy a full growing season, and before it’s over, they may need a bigger pot to grow in. To repot your galaxy flowers, start by picking a pot one size larger than its current pot. Then, fill the new pot with a fresh, disease-free, and loosely packed potting mix

Gently remove your plant from its current pot, careful not to damage the roots. Finally, place the plant in the new pot, and fill in around it with more potting mix.



How to Propagate Galaxy Flowers

While galaxy petunias are technically perennials, they rarely survive the cold weather. Consequently, most bedding plants are produced annually from flower seeds

Fortunately, galaxy flowers are relatively easy to propagate. Follow these four easy steps: 

  1. Take a cutting from an existing plant. 
  2. Place it in water or moist soil. 
  3. Keep the cutting in a warm, sunny spot and wait for new growth to appear. 
  4. Once the plant has rooted, transplant it into a pot or garden bed

To care for your galaxy flowers, plant them in well-drained soil and water them regularly.



Common Issues with Galaxy Flowers

Although galaxy flowers are uncommonly easy to grow in baskets, flower beds, or gardens, they are susceptible to various conditions and adverse growth environments.


Like most other plants, galaxy flowers are susceptible to diseases. Botrytis, Rhizoctonia, and Pythium are three diseases commonly found in galaxy flowers. You can usually avoid Botrytis by allowing your soil to dry between waterings. Improving drainage and aeration can prevent Rhizoctonia. You probably need to invest in a fungicide if your plant gets Pythium. 

Inadequate Sunlight

Galaxy flowers need a lot of sunlight. Without enough of it, the flowers will not be able to grow properly, and the plant quality will be reduced. Low light levels can result in delayed flowering, excessive vegetation growth, or stretched plants. 


Excessive vegetation growth occurs when your plant has many leaves and few blossoms. Possible reasons for overgrowth include over-fertilization, high ammonia concentration in the soil, low light levels, overwatering, and wet media.

Tightly Packed Soil

To grow galaxy flowers, the soil needs to be well-drained. If the soil is too dense, the water will not reach the roots, and the flowers will not be able to get the nutrients they need. 

You can tell if your soil is tightly packed by noticing how long the dirt takes to absorb water. If you notice water pooling on top, your soil is too tight. You might also observe some of your plant’s leaves starting to yellow from lack of water and nutrient absorption. 

Adding earthworms or organic materials, such as peat moss, can help loosen up your soil.


Aphids, thrips, fungus gnats, whitefly, and leafminers are all common pests that can attack galaxy flowers. A professional pest control service can help prevent bug infestations and improve plant health.



Our Recommendation

Galaxy flowers add an aesthetic flair that’s almost out of this world. They’re unique, fun plants that require only moderate care if planted in bright, sunny locations. Galaxy flowers can add cosmic color to your flower beds or hanging baskets, or they can make unique gift ideas for Mother’s Day or another holiday. 

You can propagate a cutting from a friend’s plant, start your galaxy flowers from seed, or buy a young plant at the garden shop. If you are seeking a full-grown galaxy flower, consider purchasing one from an Etsy shop for a memorable Valentine’s Day gift or another flower gift.



Galaxy Flower FAQ

Are galaxy flowers real?

Galaxy flowers are real. Antonella Capo, a plant breeder in Italy, created them by cross-breeding two existing petunia flowers to create a new hybrid flower. Known for its deep color and dotted with white speckles, galaxy flowers resemble the clear night sky filled with a constellation of stars. 

What are galaxy flowers called?

A galaxy floweru0026#8216;s botanical name is petunia cultivars. A type of petunia—just like the colorful, fragrant blooms you see draped from hanging baskets—galaxy flowers are a deep purple. They earned their name due to the white spots speckled on their petals, which look like the stars of the Milky Way. 

How often should I water night sky petunias?

Galaxy flowers are easy to care for, but they are tropical plants that need plenty of water. Water them just before the soil gets dry. Adjust your water volume upward in dry weather, and slack off just a little when it’s rainy.