Updated/Fact-Chacked on April 20, 2023 by Gareth James
We previously wrote about all the outdoor black flowers available for gardeners to grow, with many new varieties appearing over the last 10 years. Being big Dahlia lovers, we dedicated an entire post to growing black dahlias – embrace the dark side.
Over the years, people have done cross-pollination to produce various varieties of dark dahlias. Several of these types can be classified under “black dahlia.” That is any dahlia that gives very dark purple flowers. The colour comes close to black, depending on how much light they get. Unfortunately, no flower can be developed pure black; it is impossible.
Every variety of these dark dahlias may show different shapes. Also, their size can vary from 2 to 3 inches and expand to almost a foot.
In this guide, we will teach you everything you need to know about black (dark) dahlias. This will include how to grow and care for them.
A Brief History of Black Dahlias
Dahlia is a term that refers to hundreds of species in the genus Dahlia. As stated above, any of these flowers with dark red or dark purple flowers are considered black dahlia.
History has it that dahlias generally came from mountainous regions of Mexico. It’s also linked to a few locations in Guatemala and other regions of Central America. The plants grow as perennials here because the weather has no hard frosts.
While the plants have produced flowers ever, early adaptors valued them for other benefits too. For instance, indigenous people used tubers for food. The long hollow stems were used in building water pipe systems.
It was not until the 18th century that dahlias came to Europe. They started in Spain with tuber and seeds before spreading to other European regions.
Today, people have crossed the flowers to produce a wide range of varieties. You will see different types of black dahlias everywhere in the UK.
Features of the Black Dahlia
Black dahlia belongs to the Asteraceae family. These are perennial plants that grow in warm weather from underground tubers.
During spring, the tubers germinate with green, vegetative shoots. As time goes by, multiple layers of branching shoots grow. Then bobbed flowers cover them.
Since there are different species and varieties of black dahlias, their height also varies. Most of them grow up to three or five feet.
Even though they are called black, understand that these flowers are not truly black. Some are deep dark purple, while others have shades of red that may look like black under the right conditions.
Flowers and shapes also vary depending on the specific types. They can grow from a few inches to a foot in diameter. Hence, they are classified according to colour, flower appearance, and size.
What is the Meaning and Symbolism of Black Dahlia?
What came to your mind when you first heard the phrase ‘black dahlia?’ For many people, it’s not a beautiful flower that crosses their minds. Instead, they might think of some heartless murder or unresolved story.
This should not come as a surprise, considering flower symbolism is mainly related to their colour. The size and shape are rarely considered.
Naturally, therefore, black dahlias are often viewed to convey negative emotions. They are highlighted where, for instance, betrayal and sadness are present.
However, symbolism in dark-coloured flowers should not be subjected to such negativity at first glance. It could be one way, but not the only way. In this case, the dark purple in black dahlias can also represent passion and power.
The colour black is also seen as the most elegant of all. Hence, the flowers with the colour can bring some elegance and exposure to the garden. Besides, when you mix colours, it changes the symbolism of single-colour flowers.
Combining other dahlias with black dahlia creates contrast and eliminates the possible negativity associated with their colour.
How to Grow Black Dahlia
Follow the steps below, and you will have the incredible, dark-blooming flower.
The Best Time to Plant
Black dahlia flowers are technically perennials, but they are planted as annuals in many parts of the UK. That is because the plants and their tubers cannot withstand extremely low temperatures.
So, if winter goes below freezing weather in your area, consider planting them during spring. You can then dig them when autumn comes.
If you are planting them directly in the soil, keep them safe until after the frost. Also, do not plant until the soil warms above 15 C.
You can also pre-sprout tubers indoors. Do this 4 to 6 weeks before you transfer them outside. With that, you will have jump-started the season, helping your black dahlias to bloom much sooner.
You will need a shallow crate full of potting soil (a little moist) for indoor germination. Then place the containers in a warm environment.
Give the tubers a few weeks, and you will see them sprouting. Wait until the outdoor conditions are favourable before transferring.
Dahlias are known to be long flowering; once established, you will get flowers throughout autumn until the first frost.
How to Plant Black Dahlias
Under optimal outdoor conditions, certain dark dahlia varieties can grow up to 4 feet tall. In a flower pot, they may only grow to around 1 foot.
Black dahlias can grow well both indoors and outdoors. Since they bloom wide flowers, they need a lot of energy. And that is why they may not bloom indoors if they don’t get sufficient light.
Wait until the soil warms up before planting the tubers. Dig about four to six-inch deep holes, depending on the size. Ensure you follow the right orientation.
For pre-sprouted tubers, grow them facing upward. But if you had not pre-sprouted, find a round eye and place it in the hole facing up. Now cover the tubers well.
Follow these same steps if you are planting them in containers. You need to ensure the tubers are always well covered.
What is the Best Soil?
The best soil for black dahlias should be rich and well-drained. You can use compost to increase drainage in your soil. Adding nutrients should also be great if the soil is heavy.
You can also amend your soil by digging it properly before adding compost. The goal is to get the soil ready for the tubers.
Natural to slightly acidic pH is perfect for the flowers. Keep this between 6.0 and 7.0. If your soil has lower pH, add in some elemental sulfur. Garden lime will also raise the pH.
How About Sunlight
Black dahlias use a lot of energy when blooming. Hence, ensure you plant them in an area that gets at least 8 hours of direct sunlight daily to have a long flowering dahlia.
The flowers can handle a bit of shade. But they will only produce a few flowers. This is why dahlias cannot grow very large indoors.
How Much Water to Use
Watering is another crucial part of growing black dahlias. Do not water the tubers before they sprout. They may rot if you do this, especially in cooler soil.
Water the soil about once a week after the tubers have sprouted. You want to avoid dry and saturated soils. Deep and infrequent watering is most advised.
Black dahlias will grow well even without additional nutrients. However, some regular use of fertilizers will benefit them more.
You must choose the correct product, though. Use fertilizers that are loaded with potassium and phosphorus more than nitrogen. This encourages better flowering.
Timing is also crucial. Fertilize the soil about a month after moving them outdoors. Ensure the product instructions are followed to the end.
How to Stake
Healthy black dahlia can grow up to five feet tall. Therefore, staking might be more beneficial in keeping the plants upright – especially in you live in a windy area as I do in the North East.
Insert the stake after planting your tubers to avoid damaging them. Or you can stake them once every few feet.
You can either use singular stakes or cages. Either way, you will still get great results.
Pinching the Plants
You can get more flowers by pinching your black dahlia. This might delay the first flowering, but it will increase the flower yield.
Pinching or topping is the removal of terminal buds at about 1 foot tall. Your plant should have about four leaves. Use hands and scissors to remove the bud, avoiding the leaves carefully.
Varieties of Black Dahlia
Each year different varieties of black dahlia appear; here are a few that are readily available.
- Dahlia ‘Black Jack’ – They are also called ‘dinner plate’ because they grow to the size of a dinner plate. The flowers are very dark, almost black.
- Dahlia ‘Black Embers’ – They are a bit lighter and produce deep red flowers, darker at the centre. The flowers are relatively smaller.
- Dahlia ‘Black Satin’ – Similar to black embers but much smaller in diameter.
- Dahlia ‘Arabian Night‘ – Even smaller flowers that reach only 4-inches in diameter. They are visually similar to black satin and embers.
- Dahlia ‘Chat Noir’ – Tall stemed, dark dahlia variety used for cutting flowers
- Dahlia ‘Black Wizard’ – Another dark cactus variety
- Dahlia ‘Sam Hopkins’ – Dark red variety with almost black buds
- Dahlia ‘Honka Black’ or ‘Verrone’s Obsidian’ – Highly unusual dahlia, perfect for adding drama to any border.
- The breathtaking Verrone’s Obsidian in bloom
Every variety is unique. You can try mixing different varieties to get better results.
Which Common Issues Can You Expect With Black Dahlia
The greatest thing about black dahlia is that they are not prone to disease. But you must meet the growth requirements. Nevertheless, here are some of the issues you may meet:
- Rotting. This happens due to overwatering. Just reduce the watering frequency to resolve this.
- Pests and diseases. Some fungal and viral pathogens may infect dahlias. They will cause brown spots on the leaves. Destroy the affected plant before it spreads the virus.
- Poor lighting. Poor light is equal to slow growth and no flowering. Good lighting will give your plant the strength to grow well while keeping viruses away.
As stated above, black dahlia can grow perfectly well if you take good care of them. Watering and lack of enough light are the major problems. Take care of these, and you have great plants.
Can You Eat Black Dahlias?
Yes. You can eat the tubers or flowers of black dahlia. However, you should be very careful with them.
Black dahlias are often thought of as ornamentals rather than edibles. Hence, they are sometimes treated using harmful chemicals. So, always take caution about the source before consuming them.
The plants are toxic to dogs and cats. Keep your pets from eating them.
Where to Buy Black Dahlias this Season
I’ll try and keep this section up to date with what online stores have in stock. Note any special dahlias will sell out very quickly.
Farmergracy.co.uk – Dahlia ‘Honka Black’
syn. Dahlia ‘Verrone’s Obsidian
Crocus.co.uk – Dahlia ‘Tamburo’, Dahlia ‘Black Narcissus, Dahlia ‘Black Jack’, Dahlia ‘Dark Spirit, Dahlia ‘Karma Choc’ (PBR), Dahlia ‘Sam Hopkins’
Sarahreaven.co.uk – Dahlia ‘Black Jack’ tubers
Ashridge Nursery – Dahlia ‘Black Narcissus
Black Dahlia FAQS
What is the darkest dahlia?
The darkest dahlia is often considered to be the ‘Black Narcissus’ or the ‘Karma Choc’ variety. These dahlias have deep maroon or chocolate-coloured petals that appear almost black, especially in low light conditions or from a distance.
What is the best Black Dahlia flower?
The best black dahlia flower depends on individual preferences for colour, size, and shape. we personally love Verrone’s Obsidian.
Are black dahlias naturally black?
Black dahlias are not naturally true black. The dark colouration comes from a combination of deep red, purple, or maroon pigments in the petals. However, they appear black or nearly black, especially in low light conditions or from a distance.
Where do black dahlias grow?
Black dahlias can be grown in a wide range of climates, but they thrive in well-drained soil and full sun. They are native to Mexico, Central America, and Colombia but have been cultivated worldwide in temperate regions, including North America, Europe, and Asia.
What do black dahlias smell like?
Black dahlias generally have a mild, pleasant fragrance. The scent varies depending on the specific variety, and some may have a more pronounced fragrance than others. In general, dahlias are not known for their strong or distinctive scents but rather for their stunning visual appearance.
Are black dahlias rare?
Black dahlias are relatively rare compared to other dahlia colours, but they are not exceedingly rare or difficult to find. They are popular among gardeners and floral enthusiasts for their striking appearance and unique colouration. Many specialised nurseries and online retailers offer black dahlia tubers or plants for sale.
John Green is a 46-year-old graphic designer living in Durham. John is RHS level 3 certified and owns an allotment in Durham.