Ambition Dahlia Tubers

• Variety: Ambition
• Type: Semi-cactus (fimbriata: petals with forked, split tips)
• Colour: Magenta-purple
• Flower size: Up to 15cm (6in) across
• Height: 100cm
• Spread: 60cm
• Flowering: July to November
• Cutting: Excellent. Strong upright stems, very good vase life
• Rain resistance: Better than average. Cactus petals shed water more readily than flat decorative types
• RHS AGM: No
• Sold as: Single tubers, hand-graded, Dutch first-class quality
• Plant outdoors: March to July, when soil reaches 15°C (typically May in most of the UK)
• Delivered: From March. Collection from Castle Cary also available

Ambition: Spiky, Purple and Completely Unbothered by Rain

If you've ever watched a decorative dahlia collapse into a soggy mess after a heavy shower, Ambition is the antidote. The semi-cactus petals are rolled and quilled rather than flat, so water runs off instead of pooling in the bloom and rotting it from the inside. In a wet British summer, that's not a minor detail.

The petal tips are forked, split like tiny deer antlers. It gives each flower a slightly shaggy, textured look that's far more interesting than the smooth perfection of a decorative type. The colour is a saturated magenta-purple that holds from first bud to last petal drop. No fading, no shifting. At 15cm across, the flowers are large enough to hold their own in a border but manageable in a vase.

The stems are strong and upright, the plant produces masses of blooms from July right through to November, and the whole thing stays relatively compact at a metre tall. Plant in groups of three at 75cm spacing and you'll have a solid block of purple from midsummer to the frosts. It's a favourite of Sarah Raven, which tells you most of what you need to know about its reliability.

What to Plant with Ambition

Saturated purple works best either with similar deep tones or against deliberate contrast. For a rich, moody border, try Ambition with the near-black blooms of Dark Spirit and the deep red spikes of Rip City. For contrast, the warm blush tones of Arbatax (white with pink edges) make the purple sing, or try the velvety maroon waterlily form of Sam Hopkins for a different flower shape in the same dark palette. The heritage apricot of Preference (another semi-cactus, introduced in 1911 and still going) provides a warm, unexpected companion. Ornamental grasses soften the effect: Stipa tenuissima or bronze Carex catch the light between the flower heads.

Why Ashridge?

Our dahlia tubers are Dutch first-class quality, imported direct and hand-graded. We discard undersized tubers so you get a clump with viable eyes, ready to grow. Delivered by next-day courier from March, with our one-year plant guarantee, Feefo Platinum Service Award, and real people on the phone in Somerset if anything isn't right. Browse our cactus dahlia range or the complete dahlia collection.

Frequently Asked Questions

What's the difference between a semi-cactus and a decorative dahlia?

Petal shape. Decorative dahlias like David Howard have broad, flat petals that lie open. Semi-cactus types like Ambition have petals rolled or quilled for at least half their length, giving a spikier, more textured appearance. The practical difference is rain resistance: rolled petals shed water, flat petals hold it.

What are fimbriata petals?

Ambition is sometimes classified as a fimbriata dahlia because the tips of its petals are forked or split. Think tiny deer antlers. This gives the flowers a slightly shaggier, more informal texture compared to a smooth-petalled cactus dahlia. Same plant either way. Fimbriata is just a more specific description of the petal tip.

What happens if I go on holiday and can't deadhead?

The plant won't die, but it'll slow down. Once a dahlia sets seed, it puts less energy into new flowers. You'll come back to a few spent heads, possibly some developing seed pods, and fewer buds in the pipeline. Cut everything spent back hard when you return and give it a good feed. It'll pick up again within a couple of weeks.

Will Ambition grow in a pot?

Borderline, at a metre tall with 15cm flowers. A large pot (at least 35cm across and deep) with rich compost, a cane and regular liquid feeding will work, but it'll always do better in the ground. For a purple dahlia that's truly happy in a container, something more compact would suit. Our pots and containers guide has the details.

Do dahlias have a scent?

Barely. Most dahlias have little to no fragrance. A faint earthy, green note if you bury your nose in them, but nothing you'd notice from a distance. They earn their place through colour and form. If you want scent in the same border, plant them with late-flowering sweet peas or nicotiana.