Can You Plant Onion Sets in March?

Yes — March is one of the best months to plant onion sets in the UK. For most gardeners, March offers the perfect balance of improving soil conditions, rising temperatures, and reduced risk of bolting.

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This guide explains why March planting works so well, what conditions to look for, and how to get the best results from your onion sets.

Why March Is Ideal for Planting Onion Sets

March is often considered the sweet spot for planting onion sets in the UK.

Benefits of March planting include:

• Warmer soil temperatures
• Faster root establishment
• Reduced risk of bolting
• Strong, steady growth

By March, daylight levels are increasing and the soil is beginning to warm, allowing onion sets to establish without stress.

For a complete overview of onion growing, see ONION SETS UK: THE COMPLETE GUIDE TO PLANTING, GROWING & HARVESTING ONIONS.

What Soil Conditions Are Best in March?

Before planting onion sets in March, check that:

• Soil is workable and crumbly
• Beds are free-draining
• There is no standing water

March soils are usually far easier to work with than February, particularly on heavier ground.

If your soil still holds water, growing onions in raised beds or containers can help. See HOW TO GROW ONIONS IN CONTAINERS for an alternative approach.

Is March Better Than February for Planting Onion Sets?

For most UK gardens, March is safer and more reliable than February.

March planting reduces the chance of:

• Cold stress
• Bolting later in the season
• Rotting onion sets

If you’re deciding between the two months, see CAN YOU PLANT ONION SETS IN FEBRUARY for a detailed comparison.

Can You Plant Onion Sets at Any Time in March?

Yes, but timing still matters.

• Early March: Fine in mild regions and free-draining soil
• Mid to late March: Ideal for most of the UK
• End of March: Still suitable, especially in colder areas

Gardeners in northern or exposed areas often get better results by planting towards the middle or end of the month.

For region-specific guidance, see WHEN TO PLANT ONION SETS IN THE UK.

What Temperature Should the Soil Be in March?

Onion sets can be planted once soil temperatures are consistently above 5°C.

In March:

• Daytime warmth encourages root growth
• Cold nights are less damaging than earlier in the year
• Growth is steadier and less stressed

For more detail, read WHAT TEMPERATURE CAN ONION SETS BE PLANTED.

How to Plant Onion Sets in March

Planting in March follows the same method as other spring plantings:

• Space sets 10–15 cm apart
• Leave 25–30 cm between rows
• Plant with the tip just showing above the soil
• Firm gently and water well

Correct spacing helps prevent competition and stress. See HOW FAR APART TO PLANT ONION SETS for more guidance.

Are There Any Risks to March Planting?

Risks are minimal, but still include:

• Late cold snaps
• Very wet soil in heavy ground

These risks are far lower than earlier plantings and usually easy to manage.

If onions experience stress early on, they may bolt later. Learn how to avoid this in WHY ONIONS BOLT AND HOW TO STOP IT.

When Should You Delay Planting in March?

Delay planting if:

• Soil is waterlogged
• Frost is forecast for several consecutive nights
• Beds haven’t warmed at all

Waiting a week or two in March rarely causes problems and often improves results.

Summary: Should You Plant Onion Sets in March?

• Yes — March is ideal for most UK gardeners
• Provides the best balance of warmth and stability
• Lower risk than February planting
• Suitable across most regions

For everything else you need to know about growing onions from sets, return to ONION SETS UK: THE COMPLETE GUIDE TO PLANTING, GROWING & HARVESTING ONIONS.

Related Onion Growing Guides

• WHEN TO PLANT ONION SETS IN THE UK
• BEST ONION VARIETIES FOR UK GARDENS
• WHY ONIONS BOLT AND HOW TO STOP IT
• HOW TO GROW ONIONS IN CONTAINERS
• PICKLED RED ONION RECIPE