Deeper, Richer Color on a Tidy Summer Allium

Cobalt Millenium Allium (Allium 'Cobalt Millenium') builds on the beloved Millenium with even deeper, more saturated cobalt-purple flower globes in mid to late summer. Like its parent it's a tidy, clumping ornamental onion with neat grassy foliage that never flops or spreads, and its richly colored blooms are a magnet for bees and butterflies. Tough, drought-tolerant, and deer-resistant, it's an easy, eye-catching choice for sunny Edina, Maple Grove, and Woodbury borders.

Landscape Uses

Use Cobalt Millenium in pollinator and sunny borders, mass plantings, edging, and containers. Its rich color and tidy habit pair beautifully with coneflowers, ornamental grasses, and sedum, and the flowers cut well.

Best Time to Plant

Plant in spring or early fall, when cooler weather and steady moisture help roots establish.

How to Plant

Dig a hole twice as wide as the root ball and just as deep. Set the crown level with the soil, backfill, water in well, and mulch 2–3 inches deep.

Watering

First Year: Water deeply 1–2 times per week to establish the roots.
After Year One: Water during dry spells. Allium is quite drought tolerant once established.
Drip Irrigation: A drip line provides efficient, low-water moisture.

Frequently Asked Questions

How is it different from Millenium?
It offers a deeper, more saturated cobalt-purple flower color on the same tidy, reliable clumping plant.

Does it spread or flop?
No, it forms a neat clump that stays put.

Is it hardy in Minnesota?
Yes, hardy to Zone 4 and reliable across most of the state.

Is it deer resistant?
Yes, the onion scent makes alliums highly deer- and rabbit-resistant.

You May Also Like

Pair Cobalt Millenium with Millenium and Summer Beauty allium, coneflowers, and grasses for a pollinator-friendly summer border.