PlantSowGrow
How to grow Allium (Purple Sensation)
Allium hollandicum 'Purple Sensation'
Also called ornamental onion, flowering onion, Persian onion, Allium aflatunense
Striking purple drumstick flower balls in May and June, adored by bees. Seedheads look great into summer.
At a glance: Sow early September to mid October.
When to sow, plant and harvest
Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.
Growing Allium (Purple Sensation): what it needs
- Light
- Full sun · 6+ hours a day
- Watering
- Water pots in dry spells while in leaf; keep drier when dormant
- Soil
- Well-drained soil or bulb compost
- Spacing
- 20 cm
- Height
- 90 cm
- In pots
- Grows well in containers
- Feeding
- A little general feed in spring
- Hardiness
- USDA zones 3–8
Step by step
- Early September – mid October · 6 weeks before the first autumn frost
Plant Bulbs
Plant 10–15 cm deep and 20 cm apart, pointy end up, in well-drained soil or pots. Water in.
- 100–150 days after “Plant Bulbs” · Mid December – early February
Look for Shoots
Green shoots should be showing. Keep pots moist but not wet and watch for slugs on young leaves.
Every year
- MayIn Flower
Your bulbs should be in flower — a good moment for a journal photo.
- JuneDeadhead and Feed
Snap off faded flower heads (not the leaves) and give a high-potash feed to build up the bulb for next year.
- JulyLet the Leaves Die Back
Leave the foliage for at least six weeks after flowering, until it yellows — don't knot or cut it. Then tidy it away.
