Onions and garlic are essential allotment crops. They take up relatively little space, store well, and are used in almost every kitchen. They’re also excellent beginner crops — as long as they’re grown slowly, with the right spacing and good soil.

This guide covers how to grow onions and garlic from seed, sets, and plug plants, when to plant, spacing, watering and feeding, pests and diseases, container vs ground growing, and proven ways to improve yields.

🌱 1. Ways to Grow Onions & Garlic

🌰 From Seed (Onions only)

Growing onions from seed gives the best flavour and storage potential.

Pros

• Cheapest option

• Huge variety choice

• Excellent long-term storage

Cons

• Slower to establish

• Needs early sowing and patience

🧅 From Sets (Onions)

Small immature onions grown on for planting.

Pros

• Fast and reliable

• Ideal for beginners

• Less weeding early on

Cons

• Slightly more expensive

• Higher risk of bolting

🌱 Plug Plants (Onions & Garlic)

Young plants supplied ready to grow.

Pros

• Great for late planting

• Strong, uniform plants

Cons

• Higher cost

• Limited variety choice

🧄 Garlic Cloves

Garlic is grown by planting individual cloves.

Always use:

• certified garlic bulbs
  Avoid supermarket garlic if possible — it may carry disease or be treated.

🗓️ 2. When to Plant Onions & Garlic

Onions

• From seed (indoors): Jan–Feb

• From seed (outdoors): Mar–Apr

• From sets: Mar–Apr

• Overwintering sets: Oct–Nov

Garlic

• Autumn planting: Oct–Nov (best yields)

• Spring planting: Feb–Mar

Autumn-planted garlic usually produces larger bulbs.

🌾 3. How to Grow Onions & Garlic in the Ground

Soil Requirements

• Free-draining soil

• Open, sunny position

• Not freshly manured

Too much nitrogen = leafy growth and poor bulbs.

Spacing

Onions

• 10–15cm between plants

• 30cm between rows

Garlic

• 10–15cm between cloves

• 30cm between rows

Crowding leads to small bulbs.

Planting Depth

• Onion sets: tip just showing above soil

• Garlic: plant cloves 5–7cm deep, point up

🪴 4. Growing Onions & Garlic in Containers

Ideal for:

• small plots

• patios

• poor or heavy soil

Container Guidelines

• Minimum depth: 20–25cm

• Free-draining compost

• Good drainage holes

Spacing in pots:

• 1 onion per 10cm

• 1 garlic clove per 10–12cm

Water containers more regularly than ground beds.

💧 5. Watering Onions & Garlic

Watering Rules

• Water during dry spells, especially early growth

• Reduce watering once bulbs start swelling

• Stop watering completely as foliage yellows

Too much water late on causes:

• soft bulbs

• poor storage

🌿 6. Feeding Onions & Garlic

Onions and garlic are light to moderate feeders.

Best Practice

• Add compost before planting

• Avoid high-nitrogen feeds

• Optional light feed in spring if growth is weak

Strong soil structure matters more than fertiliser.

🐛 7. Common Pests & Diseases

Onion Fly

Symptoms

• Wilting plants

• Maggots in bulbs

Prevention

• Fine mesh netting

• Crop rotation

• Avoid thinning seedlings in open air

White Rot (Serious Disease)

Symptoms

• Yellowing leaves

• White fungal growth on bulbs

Prevention only

• Strict crop rotation (8+ years)

• Use clean seed/sets

• Remove infected plants immediately

Leek Rust (Affects onions too)

• Orange pustules on leaves

• More common in damp summers

Improve airflow and avoid overcrowding.

🧺 8. Harvesting & Storage

When to Harvest

• When foliage turns yellow and falls over naturally

• Do not force tops down

Drying (Curing)

• Lift bulbs carefully

• Dry in a warm, airy place for 2–3 weeks

Storage

• Store dry, cool, and frost-free

• Use soft or damaged bulbs first

🌾 9. Improving Yields 

• Start early (especially from seed)

• Give plants space

• Keep beds weed-free

• Avoid rich, nitrogen-heavy soil

• Choose the right planting season

Slow, steady growth produces larger, better-storing bulbs.

⚡ 10. Quick Growing Tips

• Weeds are the biggest enemy of onions

• Mulch lightly once established

• Don’t overfeed

• Rotate crops regularly