When to Sow Nasturtium Seeds in the UK

Knowing when to sow nasturtium seeds in the UK is essential for strong growth and long-lasting flowers. Nasturtiums are quick-growing, easy annuals, but they are frost tender, so sowing them at the right time makes a big difference to success.

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This guide explains the best sowing times for nasturtium seeds in the UK, whether you plan to start them indoors or sow them directly outside.

Best Time to Sow Nasturtium Seeds in the UK

In the UK climate, nasturtium seeds are best sown in spring, once temperatures begin to rise.

Recommended sowing times:

Indoors: March to April
Outdoors: Late April to May
Flowering period: June to October

Outdoor sowing should only take place once the risk of frost has passed, as young nasturtium seedlings are easily damaged by cold weather.

When to Sow Nasturtium Seeds Indoors (UK)

Starting nasturtiums indoors is ideal if you want earlier flowers or need to protect seedlings from slugs.

Best indoor sowing time:

Mid-March to April

Seeds should be sown individually in pots, as nasturtiums dislike having their roots disturbed. Keep them in a bright, frost-free place and harden them off gradually before planting outside.

When to Sow Nasturtium Seeds Outdoors (UK)

Direct sowing is simple and works very well once the soil has warmed.

Best outdoor sowing time:

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March is when the growing season truly begins. Seeds are being sown daily, beds are prepared and late frosts are still possible — these essentials help produce strong plants and a successful start.

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Late April to May
After the last frost
When soil feels warm and dry

Cold or waterlogged soil can cause seeds to rot or germinate poorly, so patience is key.

Can You Sow Nasturtium Seeds Too Early in the UK?

Yes. Early sowing is one of the most common mistakes UK gardeners make.

Problems caused by sowing too early include:

Poor germination
Seed rot in cold soil
Frost-damaged seedlings
Weak, slow growth

It is always better to wait an extra week than risk sowing too early.

Regional Differences Across the UK

Sowing times can vary slightly depending on location.

Southern UK: Outdoor sowing often possible from mid to late April
Midlands & Northern England: Late April to early May
Scotland & higher ground: May is usually safest

Local weather conditions matter more than calendar dates.

Can You Sow Nasturtium Seeds Later in the Season?

Yes. Nasturtiums are very forgiving.

Seeds sown in June will still grow and flower
Warm soil speeds up germination
Later sowings extend colour into autumn

This makes nasturtiums ideal for staggered sowing.

Final Thoughts: When to Sow Nasturtium Seeds in the UK

In the UK, the best time to sow nasturtium seeds is March to April indoors or late April to May outdoors, once frost risk has passed and the soil has warmed. Waiting for suitable conditions results in healthier plants, better flowering, and fewer problems.

Easy to grow and fast to establish, nasturtiums reward patient spring sowing with months of colour and edible harvests.

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