Dahlia Imperialis (The Tree Dahlia)

Dahlia ‘Imperialis’ is unlike any other dahlia in the garden, bringing true architectural scale and a late-season floral display. In ideal conditions, this tree dahlia can reach 3–5 metres tall, producing tall, bamboo-like stems topped with sprays of elegant blooms held high above the planting. The flowers are simple and refined, with soft lavender to pale pink petals surrounding a bright golden centre. Each bloom measures around 7–10 cm across, but they appear in clusters, creating a light, airy canopy of colour rather than a single focal flower. The overall effect is delicate and cloud-like, especially when seen against the sky.

Flowering typically begins in autumn, often later than most other dahlias, bringing colour when many summer plants are fading. In milder regions, flowering is more reliable before the first frosts, while in cooler areas performance depends on a long, warm growing season. In the garden, Dahlia ‘Imperialis’ is best used as a structural feature rather than a border plant. It thrives in a sheltered, sunny position, ideally against a wall or fence where the tall stems are protected from wind. Due to its scale, it naturally becomes a focal point and is often grown as a seasonal “living screen” or backdrop planting.

Although not used in the traditional sense as a cut flower, its towering presence and floral canopy create a dramatic garden effect that adds a completely different vertical layer to planting schemes.

For best results, plant in spring after the risk of frost has passed in rich, well-drained soil with plenty of space to develop. Support may be required in exposed sites. In colder parts of the UK, tubers should be lifted and stored over winter, as this variety is not fully frost hardy.

A spectacular tree dahlia that delivers height, elegance, and a striking late-season display few plants can match.