All About Alliums: Spring Bulbs vs. Summer Perennial Blooms

There is something absolutely whimsical about alliums rising above a cottage garden bed. Their globe-shaped blooms float like little fireworks above roses, nepeta, and peonies, structured yet whimsical at the same time. If you’ve followed along at Old Castle Cottage, especially in my posts on Everything You Need to Know About Alliums and The Whimsy of Alliums – you know I rely on alliums heavily in my Zone 6b Connecticut garden for structure, deer resistance, and pollinator support.

But one thing that often confuses gardeners, and was actually the inspiration for this post: what is the difference between spring allium bulbs and perennial summer alliums?

Let’s break it down and then I’ll share how I plant them for succession, so you have blooms from May through August.

Spring-Blooming Allium Bulbs (Planted in Fall)

These are the large ornamental alliums most people picture, tall stems with dramatic round blooms.

Key Characteristics:

• Planted in fall (like tulips and daffodils)
• Bloom in late spring to early summer (May–June in Zone 6b)
• Grow from a bulb
• Most do not rebloom the same season
• Foliage often fades yellow as blooms appear

These bulbs create architectural height right when your roses and peonies are beginning to shine. They look the best when planted in mass.

Favorite Spring Allium Bulbs for Succession:

Bloom Type	Variety	Height
Early-Mid Spring	Allium Purple Sensation	24-30″
Mid-Spring	Allium Mount Everest (white)	36-40″
Late Spring	Allium Giganteum	40-48″
Late Spring	Allium Globemaster	30-36″
Late Spring	Allium Ambassador	40-48″

Planting Tip:
Plant bulbs 6–8 inches deep, in well-drained soil. I love layering them behind roses and in drifts between nepeta and salvias so the fading foliage gets hidden naturally.

Perennial Alliums (Summer Bloomers)

Perennial alliums are completely different from spring bulbs.

Key Characteristics:

• Planted in spring or fall
• Bloom in mid to late summer
• Grow from a clumping root system (not a true fall-planted bulb)
• Come back reliably every year
• Foliage remains attractive
• Excellent for pollinators

How to Plant Alliums for Continuous Bloom

If you want months of color (and I know we do!), plant both types strategically.

Step 1: Fall: Plant Spring Bulbs

Layer varieties by bloom time:
Early: ‘Purple Sensation’
Mid: ‘Mount Everest’
Late: ‘Globemaster’ or ‘Giganteum‘

Plant in clusters of 5–9 for impact.

Step 2: Add Perennial Alliums

In spring, plant:

• ‘Millenium’ or for mid-summer has dark green foliage, 12-18-inches, 2 inch globes
• Serendipity” for Mid Summer has blue green foliage , 15-20 inches , 2.5inch globes
• Summer Beauty’ mid-summer blooms earlier than millenium and light lilac color
• ‘Medusa’ for late summer early fall, twisting bluegreen foliage 12-24 inches

Why Alliums Belong in Every Cottage Garden

• Deer & rabbit resistant
• Drought tolerant once established
• Pollinator magnets
• Add vertical structure
• Dry beautifully for arrangements
• Seed heads add fall interest

In my own garden, I use spring alliums as punctuation marks among my David Austin roses in my parterre garden and perennial alliums as the supporting cast through the heat of July in my garden beds. I purchase my Spring allium bulbs for Colorblends and my Perennial Alliums from Jackson and Perkins (You can use my code OLDCASTLE15 for 15% of)

For those of you gardening in warmer climates perennial alliums especially shine because they tolerate heat far better than many spring bulbs.

Quick Reference: Spring vs. Perennial Alliums

Feature Alliums	Spring Bulb Alliums	Perennial
When to Plant	Fall	Spring or Fall
Bloom Time	May-Late June	June-August
Rebloom Seasonally	No	Yes
Foliage	Often yellows	Nice texture, stays neat
Best Use	Height and drama	Long summer

If you’ve ever felt like your cottage garden fades after peony and first flush rose season season, perennial alliums are your secret weapon. Layer spring bulbs for that unforgettable late-May show… then let perennial varieties carry you beautifully into late summer. That is true cottage garden succession planting.