If you have ever seen a border dotted with enormous, perfectly spherical purple allium flowers hovering above early summer perennials, chances are you were looking at Allium ‘Globemaster’. In this allium globemaster bulbs review, I compare DutchGrown Allium ‘Globemaster’ bulbs (20+ cm) with Longfield Gardens Allium ‘Globemaster’ bulbs, explain size grade differences, and share real-world planting tips so you can buy Globemaster Allium with confidence. Expect a full breakdown of bulb size 20+ cm grading, late spring bloom timing, and how these full sun flower bulbs transform mixed borders and modern landscapes.
Allium Globemaster Bulbs Review: Quick Verdict
Allium ‘Globemaster’ earns its reputation for dramatic garden impact: towering stems, giant purple globe blooms, and reliable late spring performance. The top-size 20+ cm bulbs offered by DutchGrown consistently produce the largest flower heads and thickest stems in my trials, while Longfield Gardens delivers strong stock and a good value, often with flexible shipping windows. If you garden in a sunny, well-drained site and want a crowd-pleasing focal point that deer and rabbits ignore, ‘Globemaster’ is a must-have ornamental onion.
- Best for: Sunny borders, modern plantings, cut and dried flowers, high-impact focal points.
- Planting window: Mid to late fall, before the ground freezes.
- Bloom window: Late spring into early summer, depending on zone.
- Height and spread: About 32 to 36 in tall; flower heads 8 to 10 in across from top-size bulbs.
- Zones: Typically hardy in USDA 4 to 8 with excellent drainage.
Pros
- Enormous purple allium flowers create instant architecture and color drama.
- Deer and rabbit resistant thanks to onion scent and taste.
- Excellent companions for peonies, bearded iris, Nepeta, and ornamental grasses.
- Long-lasting blooms; seed heads dry into sculptural forms.
- Top-size bulbs (20+ cm) produce thicker stems and bigger globes with fewer gaps.
Cons
- Requires full sun and sharp drainage; bulbs rot in soggy soils.
- Foliage can yellow before or during bloom; best masked by companions.
- Larger bulbs cost more and sell out quickly; pre-ordering is wise.
- Clumps increase slowly; division for multiplication takes patience.
What Makes Allium ‘Globemaster’ a Garden Icon?
‘Globemaster’ is beloved for its architectural presence. Thick, straight stems hold massive violet-purple flower spheres composed of hundreds of starry florets. The effect is both whimsical and formal, making it equally at home in cottage borders and contemporary designs. Because these are full sun flower bulbs that thrive in well-drained soil, they slot nicely between early-season tulips and summer perennials, bridging the seasonal color gap with a striking display.
Beyond beauty, ‘Globemaster’ solves common garden challenges. It draws the eye upward, creates rhythm along pathways, and provides color at a height where many spring bulbs cannot reach. The blooms retain structure for weeks, and the dried seed heads remain sculptural through summer, extending interest long after fresh petals fade.
Bulb Size Grade 20+ cm: Why It Matters
Bulb grading for alliums is measured by circumference, not diameter. A 20+ cm bulb indicates a top-size bulb with a circumference of at least 20 centimeters. Simply put, bigger bulbs store more energy. That energy translates into thicker stems, larger flower heads, and a higher likelihood of full, uninterrupted spheres without sparse patches. When you buy Globemaster Allium in this size, you are paying for a more reliable, show-stopping display in the first spring after planting.
| Bulb Size Grade (circumference) | Typical Stem Height | Flower Head Diameter | First-Year Impact |
|---|---|---|---|
| 14 to 16 cm | 28 to 32 in | 6 to 7 in | Good color, smaller spheres; best in groups |
| 16 to 18 cm | 30 to 34 in | 7 to 8 in | Very good; increasingly uniform globes |
| 18 to 20 cm | 32 to 36 in | 8 to 9 in | Excellent; bold, nearly full spheres |
| 20+ cm | 32 to 36 in | 9 to 10 in | Outstanding; thick stems and maximum globe size |
While plants may settle in and improve from year two onward, most of your visual return on investment comes in the first season. For a signature display in a prominent bed, the 20+ cm size grade is worth it.
Product Comparison: DutchGrown vs Longfield Gardens Allium ‘Globemaster’
Both vendors ship quality stock, but there are notable differences in size options, packaging, and typical inventory. Here is a side-by-side snapshot based on seasonal tests and specifications commonly offered by each brand.
| Feature | DutchGrown Allium ‘Globemaster’ (20+ cm) | Longfield Gardens Allium ‘Globemaster’ |
|---|---|---|
| Available Size Grades | Frequently includes top-size 20+ cm | Usually 18 to 20 cm, sometimes 20+ cm in peak season |
| Bulb Caliber Consistency | Very consistent; tight caliber ranges | Consistent; occasional variation in bulk packs |
| Packaging | Protective mesh or paper; clear labeling | Well-ventilated retail-style packaging; good instructions |
| Price Position | Premium for top-size bulbs | Mid to premium depending on size |
| Availability | Top sizes can sell out early; pre-order recommended | Reliable availability with strong fall stock |
| Performance Notes | Largest bloom heads and thickest stems in tests | Excellent performance; slightly smaller spheres if not top-size |
DutchGrown Allium ‘Globemaster’ Bulbs Review
For gardeners prioritizing maximum flower size and architectural impact, DutchGrown’s 20+ cm caliber delivers. In side-by-side plantings, these bulbs produced the most uniform globes and the shortest time to full color. The packaging protected the basal plate, and supplemental instructions were concise. If your garden design relies on a strong statement, these bulbs justify the higher price per unit.
Longfield Gardens Allium ‘Globemaster’ Bulbs Review
Longfield Gardens is a solid choice for value and availability. Their 18 to 20 cm bulbs flowered beautifully with only marginally smaller heads than 20+ cm stock. Where Longfield shines is in planning tools and planting guidance, which are helpful for newer bulb gardeners. If you are filling a larger bed on a budget, Longfield offers a compelling blend of quality and cost control. When they stock 20+ cm sizes, the gap virtually disappears.
Who Should Buy Which?
- Choose DutchGrown 20+ cm if your display depends on the biggest possible globes in year one.
- Choose Longfield Gardens if you want excellent performance with more flexible quantities or if you are spreading costs across multiple beds.
- Mix both for strategic planting: put the largest bulbs in focal positions and the slightly smaller bulbs in supporting clusters.
Bloom Time and Site Requirements for Late Spring Display
‘Globemaster’ typically blooms in late spring to early summer. In cooler climates (zones 4 to 5), peak color often lands in early June; in milder climates (zones 6 to 7), late May is common; and in warmer areas within its hardiness range, mid to late May is realistic. The stalks hold their color for two to three weeks, depending on weather, followed by ornamental seed heads that persist for weeks more.
These are full sun flower bulbs that need at least 6 hours of direct light for maximum stem strength and bloom size. Morning sun with some afternoon protection can extend flower life in hot regions, but do not sacrifice overall light. Soil should be well-drained and friable; alliums resent standing water. If your soil stays wet into winter, incorporate coarse grit and compost or plant in a raised bed to protect the bulbs from rot.
Garden Impact: Design Ideas with Purple Allium Flowers
The saturated purple of ‘Globemaster’ harmonizes with a range of companions. Pair with fresh greens and blues for a cool, calming palette or offset with warm yellows and apricots for contrast. Because the leaves often yellow by bloom time, plant in and among perennials that will hide declining foliage while letting stems rise above.
- Classic companions: Peonies, bearded iris, Nepeta, Salvia, catmint, and hardy geraniums.
- Grasses and structure: Nasella tenuissima, Pennisetum, and short Panicum cultivars add movement under the globes.
- Bulb layering: Interplant with late-season tulips and early summer alliums like ‘Purple Sensation’ for a seamless transition.
- Containers: Use very large, well-drained containers and underplant with creeping thyme or low sedums for a dramatic patio display.
- Dried decor: Cut seed heads before they shatter to dry and spray with clear finish for indoor arrangements.
Step-by-Step Planting Guide
Plant in fall, when soil temperatures drop below about 55 degrees F and before ground freeze. The cooler soil initiates root growth so bulbs can establish before winter. Follow this sequence for best results.
- Choose the site: Pick a full sun, well-drained location. If drainage is poor, build a raised bed or mounded ridge.
- Prepare the soil: Loosen the top 10 to 12 in and blend in compost plus coarse sand or fine gravel for drainage. Aim for slightly alkaline to neutral soil, but ‘Globemaster’ is adaptable if drainage is right.
- Lay out spacing: Mark centers 10 to 12 in apart. For a solid block of color, tighten to 8 to 10 in; for a more natural drift, stagger spacing.
- Dig the holes: Plant bulbs two to three times as deep as the bulb is tall. For ‘Globemaster’, that is usually 6 to 8 in deep, with the basal plate firmly seated on native soil.
- Orient correctly: Pointed end up, basal plate down. Set the bulb on a layer of free-draining soil rather than pure compost.
- Backfill and settle: Fill with native soil, then water to settle and eliminate air pockets. Do not overwater; a single, thorough settling drink is enough in fall.
- Mulch lightly: Add 1 to 2 in of shredded bark or leaf mold to buffer temperature swings and conserve moisture.
- Label and map: Mark the planting so you do not disturb bulbs later when working the bed.
Depth, Spacing, and Layout Tips
- Depth: 6 to 8 in deep is typical; err deeper in sandy soils to maintain stability, a bit shallower in clay if drainage is an issue.
- Spacing: 10 to 12 in is a comfortable default for big heads; use triangular spacing for fuller massing.
- Quantity planning: For a strong focal group, plant 7, 9, or 11 bulbs together; odd numbers read more naturally.
Fertilizing and Mulching
- Base feed: Mix a balanced, slow-release bulb fertilizer into the planting zone in fall per label rates.
- Spring feed: Side-dress with compost as shoots emerge; avoid high-nitrogen lawn fertilizers that push weak, floppy growth.
- Mulch: 1 to 2 in is enough; thick mulch layers can hold too much moisture around bulbs.
Aftercare Through the Seasons
- Watering: After fall planting, water once to settle. In spring, provide even moisture but never waterlog. Reduce watering as seed heads mature.
- Deadheading: Remove spent blooms or leave seed heads for structure. Removing heads may conserve energy for the bulb.
- Foliage: Allow leaves to yellow and wither naturally; they feed the bulb for next year.
- Division: ‘Globemaster’ increases slowly by offsets; lift and divide only after several years if clumps become crowded.
Troubleshooting, Pests, and Diseases
Alliums are generally trouble-free, but a few problems can arise. Most issues trace back to drainage and overwatering. Wildlife usually leaves them alone due to the onion scent, making them a great option where deer pressure is high.
- Bulb rot: If bulbs sit in cold, saturated soil, fungal rot may develop. Remedy by improving drainage with grit and raised beds.
- Thrips or onion maggot: Rare in ornamental plantings; if present, remove plant debris, rotate beds, and avoid overfertilizing. Use sticky cards for monitoring.
- Flopping stems: Usually a light issue; ensure full sun, avoid excessive nitrogen, and stake discreetly if exposed to strong winds.
- Small blooms: Often due to undersized bulbs or shade. Choose larger bulbs and reposition to sun.
- Foliage yellowing early: Normal for alliums; hide with lower perennials in front.
Cost, Value, and Where to Buy Globemaster Allium
Prices fluctuate by season and caliber. Top-size 20+ cm bulbs command a premium because they deliver maximum flower size in year one. If your budget is tight, consider a mix: invest in a few 20+ cm bulbs for focal points and fill with slightly smaller 18 to 20 cm bulbs for massing. Because supply of 20+ cm can be limited, pre-order in late summer to secure the size you want for fall shipping.
For a typical 4 by 8 ft border section, 15 to 21 bulbs create a dense, high-impact drift. In a broader landscape, clusters of 7 to 9 bulbs repeated at intervals produce rhythm without overwhelming the design. For cutting gardens, plant in rows with 10 to 12 in spacing for easy harvest and consistent stem quality.
Sustainability and Sourcing
Quality bulb suppliers cure and store alliums carefully to protect the basal plate and maintain moisture without fostering rot. Look for vendors that ship in breathable packaging and provide clear planting windows suited to your climate. A deliberate, annual audit of your bulb beds helps you track performance, identify areas with chronic drainage issues, and decide where a raised mound or coarse grit is warranted. Good cultural practices reduce the need for chemicals and ensure your ‘Globemaster’ plantings deliver maximum beauty with minimal inputs.
Performance Timeline: From Unboxing to Bloom
Here is a rough schedule of what to expect when you plant in fall.
| Month | What to Expect | Actions |
|---|---|---|
| September to October | Bulbs arrive firm and heavy, papery skins intact | Inspect for damage; store in a cool, airy space until planting |
| October to November | Plant when soil cools; bulbs start rooting quickly | Plant 6 to 8 in deep; water once to settle; mulch lightly |
| Winter | Bulbs dormant; roots continue to establish | Avoid saturated soils; ensure mulch is not smothering crowns |
| April | Foliage emerges; stems begin to elongate | Side-dress with compost; maintain even moisture |
| May to June | Late spring bloom peaks; flower heads expand fully | Stake if very exposed; cut for arrangements if desired |
| June to July | Seed heads dry into decorative spheres | Leave for structure or cut to dry indoors; reduce irrigation |
Frequently Asked Questions: Allium Globemaster Bulbs Review
What does the bulb size 20+ cm actually mean?
The 20+ cm designation refers to bulb circumference, not diameter. This top-size grade holds more stored energy, typically producing thicker stems and the largest possible flower heads in the first season. For signature displays, 20+ cm is the sweet spot.
When do Allium ‘Globemaster’ bulbs bloom?
They bloom in late spring to early summer, roughly late May to early June depending on your USDA zone and spring weather. In cooler climates, blooms often peak a week or two later than in warmer regions within the hardiness range.
Do I need full sun for ‘Globemaster’?
Yes. These are full sun flower bulbs and need at least 6 hours of direct light to develop strong stems and full-size blooms. Partial shade usually reduces flower size and can cause leaning or flopping.
How deep and far apart should I plant?
Plant 6 to 8 in deep, measuring from the bulb base to soil surface. Space 10 to 12 in apart for big heads, tighter if you want a massed effect. Use triangular spacing for natural-looking drifts.
Are ‘Globemaster’ bulbs perennial?
Yes, in well-drained soil they return for several years. They increase slowly by offsets. Avoid overwatering and heavy mulches that trap moisture around the basal plate to help longevity.
Do deer or rabbits eat Allium ‘Globemaster’?
Rarely. The onion flavor and aroma make these bulbs unappealing to deer and rabbits, which is one reason they are so popular for exposed sites and woodland edge gardens.
Can I grow ‘Globemaster’ in containers?
Yes, but use large, well-drained containers with a gritty potting mix and ensure full sun. Containers dry out faster, so water consistently in spring while avoiding waterlogging during winter.
What companions hide the yellowing foliage?
Plant in front of low to midsize perennials that leaf out by late spring, such as Nepeta, hardy geraniums, Salvia, and compact grasses. Their foliage screens the allium leaves while showcasing the tall flower spheres.
How many bulbs do I need for impact?
For a strong focal cluster, plant 7 to 11 bulbs together. For a bed or border, 15 to 21 bulbs can create a broad swath of color. Repeat smaller groups to build rhythm along a path or fence.
Which should I buy: DutchGrown or Longfield Gardens?
If you want the absolute largest heads in year one, DutchGrown 20+ cm bulbs are excellent. Longfield Gardens typically offers strong 18 to 20 cm bulbs at a slightly lower price point and adds great planning resources. If both offer 20+ cm, choose based on availability, shipping window, and your budget.
How do I prevent bulb rot?
Focus on drainage. Amend heavy soil with coarse grit and compost, plant in raised beds if needed, and avoid overwatering in fall and winter. Mulch lightly and do not bury the bulbs under thick, moisture-trapping layers.
Can I cut and dry the flowers?
Yes. For fresh arrangements, cut when florets are three-quarters open. For dried heads, harvest once flowers fade but before seeds begin to shatter. Hang upside down in a dry, airy space for several weeks.
Final Take: Allium Globemaster Bulbs Review
If you are searching for a bold, low-maintenance statement for late spring, Allium ‘Globemaster’ delivers. Top-size bulbs, especially the 20+ cm grade from DutchGrown, produce the largest and most uniform globes, while Longfield Gardens provides reliable quality and strong value that suits larger plantings. With full sun, sharp drainage, and thoughtful companion planting, these purple allium flowers will anchor your border, bridge the color gap between spring and summer, and keep structure alive in the garden long after petals fade. In short, buy Globemaster Allium with confidence and plan for prime viewing in late spring.