Crop type: Onions
Allium cepa ‘Hercules’
Common name: Onion ‘Hercules’
Crop slug: onions
This Allotment Pro editorial draft summarises the cited RHS cultivar profile and its linked crop guidance. Check the sources and adjust cultivation decisions for local conditions.RHS cultivar profile
1 - Overview
‘Hercules’ is a popular AGM onion noted for outstanding performance. It produces large, almost round bulbs with attractive dark golden-brown skins, strong flavour and good post-harvest storage. Its useful resistance to bolting adds reliability where spring temperatures fluctuate.
Grow it from spring-planted sets in full sun. Give individual plants enough room to express their large bulb size and maintain even moisture until swelling is complete.
2 - Size
- Ultimate height
- 0.5–1 metre
- Ultimate spread
- 0.1–0.5 metre
- Time to ultimate size
- one year
The tall green leaves need an open position. The RHS profile specifies 10cm between bulbs and 30cm between rows; a slightly wider plant spacing can favour especially large bulbs.
3 - Growing conditions
- Suitable soils
- Chalk, clay, loam or sand
- Moisture
- Well drained
- Preferred pH
- Neutral or alkaline
Use fertile soil improved with mature organic matter. Avoid fresh manure and winter waterlogging. Water during prolonged dry periods early in growth, then allow bulbs to ripen dry.
4 - Position and hardiness
- Light
- Full sun
- Aspect
- South- or west-facing
- Exposure
- Sheltered
- Hardiness
- H3
Full sun helps the large bulbs mature and their golden skins dry thoroughly. Protect sets from birds until roots anchor them.
5 - Colour and seasonal interest
Strong upright green foliage develops above large almost-round bulbs. At maturity, the dry outer layers become a rich dark golden brown. Flower stems are undesirable in a bulb crop and should be removed immediately.
6 - Botanical details
- Family
- Amaryllidaceae
- Native to Great Britain and Ireland
- No
- Foliage
- Deciduous
- Habit
- Clump forming
- Name status
- Accepted
Genus
Allium contains bulbous herbs with onion- or garlic-scented foliage, linear or cylindrical leaves and star- or bell-shaped flowers in rounded umbels.
Safety
The bulbs are edible. Lift and dry them gently because bruising reduces storage life.
7 - How to grow
Cultivation
Plant sets in spring in fertile, moist but well-drained ground, placing them about 10cm apart with 30cm between rows. Set each roughly 2cm deep with its tip visible. Keep rows weed-free and water in extended dry weather.
Stop watering when bulbs swell in mid-summer. Harvest after leaves yellow and topple naturally, then cure for about two weeks on racks or in a ventilated shelter before storage.
Propagation
Propagate by spring-planted onion sets.
Suggested locations
- Sunny vegetable bed
- Raised bed
- Allotment row
- Large deep container
- Sheltered kitchen garden
Pruning
No pruning is required. Remove any flower stalk promptly.
Pests
May be susceptible to onion fly. Birds may pull unrooted sets, so cover new plantings temporarily.
Diseases
May be susceptible to onion white rot, leek rust and bolting. Use rotation, free drainage and clean planting material.