Dahlia Black Jack

Dahlia ‘Black Jack’ is one of the darkest dahlias you can grow, and it has a completely different presence than the softer, pastel types. The petals are narrow, pointed, and slightly twisted, forming that classic cactus dahlia shape. The color is what really sets it apart. Deep burgundy, almost black in lower light, with flashes of dark red that come through when the sun hits the petals. It’s not a flat dark flower. There’s depth to it, especially as the bloom opens. This is a variety that adds contrast instantly. The flowers are usually around five to six inches across, with a more open, spiky form compared to decorative dahlias. Plants tend to grow around 36 to 48 inches tall, producing long, sturdy stems that hold the blooms well above the foliage. It flowers steadily from midsummer right through to the first frost if you keep cutting or deadheading.
In the garden, Dahlia ‘Black Jack’ works best when you give it space or contrast. It pairs especially well with lighter tones like soft pinks, creams, or whites, where the dark color really stands out. It also works beautifully in more dramatic plantings with deep reds, purples, and bronze foliage. The shape alone helps break up rounder flower forms.
For cutting, this is a strong performer. The stems are long and usable, and the pointed petals bring structure into arrangements. It’s often used as a contrast flower rather than a filler, adding depth and definition to bouquets.
Plant tubers in spring after the last frost once the soil has warmed. Choose a sunny position with well-drained soil and give plants enough space to develop. Because of the height and the shape of the blooms, it’s best to stake early before the stems get too tall. In colder regions of the United States, lift the tubers after the first frost and store them dry over winter.  If you want a dahlia that brings depth and contrast into your planting, Dahlia ‘Black Jack’ does it without needing anything else around it. It’s bold, structured, and noticeably different from the usual summer flowers.