Black Petunia: All You Need To Know About The Beautiful Black Flower

While there are many petunias available in a kaleidoscope of colors, one of the most popular types is the black petunia, introducing drama and elegance into any pot, bed, or border.

It’s the perfect plant if you cannot decide what should go in a bare space, but want something that will instantly catch your attention, even from a distance.

While petunias are fairly easy to look after, there are tricks to get the absolute best out of them, including the black petunia.

Before we get started, it’s worth noting that there are many black petunias to choose from, and as some are different species, they can have slightly different care requirements, but most of it will overlap.

Interested in knowing more about this fabulous plant? Here’s everything you should know.

Are Black Petunias Safe For Gardens With Pets Or Children?

Black petunias are considered safe. No part of the plant is toxic or poisonous, even if ingested, though it is best to supervise pets and children, so no damage comes to your plants, especially the likes of a black petunia, which is bound to fascinate!

How To Grow Black Petunias

If you’re growing petunias from seed, sow them about 10 weeks before the last frost, starting them off indoors.

If you prefer, you can buy plug plants or seedlings early on in spring, or, buy established plants as spring gets later. Only plant out your petunias after the last frost is over.

Sunlight And Position

For the best results possible when growing petunias, it’s a good idea to plant them somewhere that gets full sunlight for most of the day, while being under shade when the afternoon is at its fiercest, which will help the flowers last for as long as possible, and limit any sun scorch.

It’s worth knowing that petunias are not hardy plants, so you should always plant them somewhere sheltered to protect them from the cold.

They also don’t do well in very wet weather, so some sort of shelter can help them survive downpours.

Ideal Soil For Black Petunias

Petunias need plenty of nutrients to thrive, as well as decent drainage so the roots and leaves don’t rot.

If the compost in your garden is dense and doesn’t drain well, you can amend it by adding some sand and fresh compost, or it might be better to grow these plants in pots, instead.

Use slightly acidic soil, with the pH being below 7. If the soil in your garden is mostly alkaline or neutral, grow black petunias in pots, instead.

To grow black petunias in pots, use a well-draining compost mix, preferably with some perlite or coconut coir added to aerate the soil and improve drainage.

The last thing you want is compost that holds onto moisture for too long, as petunias are prone to rotting or even molding if the soil stays too wet.

Another good way to avoid this is to use unglazed terracotta pots rather than glazed ceramic or plastic.

Terracotta plant pots may be a little more pricey, but they do retain less moisture than other types of containers, and they make a great contrast against the black flowers.

You could also get your terracotta pots in bulk second-hand, usually at garage sales or auctions. Just make sure you clean them properly before planting.

When To Water Black Petunias

Exactly when your black petunias will need watering depends on the other elements of the growing conditions, but a good rule of thumb is to water them every time the top inch or two of compost has dried out if the plants are in pots.

If they are in the ground, they will need less than this, at an average of an inch of water per week, but again, it depends on the conditions. 

Water around your petunias rather than the base of the plants, as this will help curb moisture issues and rot. Let the soil pool up a little, so the roots get a decent drink.

Don’t forget to only water your outdoor plants when there’s no chance they will be in sunlight when the top of the soil is still wet, as this can burn your plants.

To avoid this, water in the early morning or evening.

When To Feed Black Petunias

It’s a good idea to give black petunias plenty of nutrients through good quality fertilizers throughout the growing season, and this will mean the plants will produce as many flowers as possible.

Use a balanced all-purpose fertilizer to start with, following the directions on the label, and when they start to bloom, swap to a flower-specific feed, and this will help the plants produce as many flowers as they are capable of, as well as sustaining them for as long as possible.

How To Propagate Black Petunias

It’s worth knowing that black petunias are treated as annual plants though they are technically perennials, as they don’t survive the cold, but you can start growing them for the following year through propagation indoors.

As they are hybrids, they also don’t produce plants from seed that will be true to the parents, so propagation via cuttings is the only way to go!

Prepare a pot before starting, using well-draining damp compost in a tray. Take some leaves from the top of your petunias, making sure that you use scissors to get as much of the leaves as intact as possible.

Plant them immediately, dipping the cut ends into rooting hormone, and then put the ends into the compost, firming down the compost a little, so they stay upright.

Leave about a 5cm gap between each leaf, so there is plenty of air circulation between them.

Put the tray somewhere cool and dimly lit for roughly three weeks. Gingerly test to see if they have rooted by pulling on one leaf between your fingers: if there is some resistance, they have rooted, and you can grow them on as rooted petunias somewhere warm and bright.

Tips On Growing Black Petunias

Pinch The Stems Back Early

When you’ve planted out your petunias, let them grow a few inches tall, and then gently pinch back the ends of the stem, which will help encourage branching growth, and more flowers later on!


When your petunias are in full bloom, they can get leggy in the height of summer, where the lower leaves will drop from the plant.

At this point, it’s a good idea to trim the stems back by a couple of inches, which will help the plant produce denser growth.

Don’t forget to pull the fading flowers off the plant, and you can do this with your fingers as the spent flowers start to dry up. They will come off easily.

Removing them helps keep the plants free of disease, but it also encourages more flowers to form.

Six Hours Of Direct Sunlight

Petunia plants need at least six hours of sunlight to stop them from growing leggy, so keep this in mind. 

Unlike some flowers that you can grow in shady areas, or even indoors, petunias need to be outside in the sun.

Black Petunia Varieties To Try Growing Yourself

There are many varieties of black petunias to choose from, including:

  • ‘Phantom’
  • ‘Black Cat’
  • ‘Black Ray’
  • ‘Back To Black’
  • ‘Black Velvet’
  • ‘Phantom’

Final Thoughts

Black petunias are one of the most striking flowers you can grow in your garden, and they aren’t complicated to grow, either.

Just keep in mind that they need lots of light, avoiding fierce afternoon sunlight, and plenty of water, but avoid poorly-draining soil, as this will cause your petunias to rot.

Switch up the fertilizer when your petunias start blooming, using a fertilizer that’s specifically for flower production.

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