Black petunias are just as easy to grow as any other variety of this lovely flower. Choose the perfect variety, plant in spring, and give them full sun and healthy soil to thrive. Regular watering and fertilizing will greatly improve blooming potential throughout summer. At the end of the season, propagate to continue to grow your favorite variety next season.
1. Choose the perfect black petunia
The term ‘black petunia’ does not describe one single plant but a group of petunia hybrids with black flowers. In this group there are several varieties to choose from with slightly different growth habits, covering the various petunia types.
Start your black petunia growing journey by choosing from these popular options:
- Black Mamba
- Black Velvet
- Back to Black
- Black Cat
- Phantom
- Black Ray
2. Plant black petunias in early spring
Petunias cannot handle cold weather and will quickly die when exposed to frost. Wait until early spring after the last frost date before planting your petunias outdoors. Warm weather encourages new root growth, too, helping the plants settle quickly.
Most black petunias are grown from seedlings or starter plants. If you prefer to grow from seed, start sowing indoors about ten weeks before the last frost date. Use a heating mat to keep the seedlings warm and they should be ready to transplant at the perfect time in spring.
3. Use the right soil mix
Black petunias need well-draining soil rich in nutrients to produce the most blooms. The soil should also be slightly acidic with a pH below 7. If you don’t have the right soil texture, amend with compost and sand to increase drainage. You can also add a handful of slow-release fertilizer if nutrient levels are low.
When planting in containers, choose a high-quality potting mix amended with coconut coir to lighten the mixture. Petunias are prone to rot if waterlogged so your potting mix and the pot itself needs to be incredibly well-draining.
4. Plant in terra cotta containers
This tip covers both design and healthy growth for black petunias – using terra cotta containers. While terra cotta is pricier than some other potting options, moisture is drawn away from the soil from all sides of the container, improving drainage.
The stunning color of these containers is also a perfect match for the stark black petunia blooms, making the flowers pop against a bright backdrop.
5. Give them full sun
Black petunias should be planted in full sun for the strongest possible flowering season. They require a minimum of six hours of direct sun per day to thrive. Any less light and you will see leggy growth and a lack of flowers.
On the other hand, black petunias are also sensitive to intense sunlight in the heights of summer. They prefer some protection during the hottest part of the afternoon to preserve the blooms and prevent scorching.
6. Pinch stems soon after planting
When your black petunias are a couple of inches tall, pinch the ends of the stems back slightly. This encourages early branching, producing more stems and later, even more flowers. Pinch the ends with your fingers or use a sharp pair of pruning shears.
7. Water when the soil dries out
Black petunias are very sensitive to overwatering, quickly rotting when soil is left soggy after watering or heavy rain. But they also can’t be left in dry soil for too long or they will begin to wilt.
For black petunias planted in beds, give them around an inch of water per week, limiting watering during rainy periods. In containers, they will need water every few days as soon as the top layer of soil has dried out.
8. Feed with a balanced fertilizer
Black petunias are known for their prolific blooming. But, for them to produce masses of flowers, they need the right nutrients.
Feed your black petunias with a balanced fertilizer soon after planting for healthy leaf, stem and bud growth. Just before the flowering season really kicks in, apply a flower-specific liquid fertilizer once every couple of weeks. This will keep the plants blooming as much as they can across the summer season.
9. Prune when stems become leggy
In the middle of summer after a long few weeks of blooming, black petunias tend to become leggy. Stems will lose their leaves at the base, making the plant appear sparse and weak.
To improve growth at this time, cut the stems back a few inches. The new growth that emerges should have denser leaf growth that makes the plant appear fuller. Also continue to deadhead to improve the look of the plant and encourage more blooms.
10. Propagate toward the end of the season
Black petunias are hybrids that don’t produce true to seed. In most climates they are also grown as annuals as they do not survive cold weather. If you want to grow your favorite black petunia again the following season, make sure you take a few cuttings to propagate indoors over winter. These are the 10 tips for growing gorgeous black petunias.
