When to Grow Sunflowers (UK Guide)

Knowing when to grow sunflowers helps you get tall plants, strong stems, and large, healthy flowers. Sunflowers are warm-season plants, so timing is important—too early and they struggle, too late and flowering can be reduced.

⭐ Recommended Products — Sunflowers & Sunflower Seeds

Sunflowers are bright, cheerful plants that are easy to grow from seed and great for gardens, borders, or kids’ projects.

• Sunflower Seed Collection (Multiple Varieties)
Includes popular types like classic tall giants, dwarf/multi-head varieties, and colourful mixes — great for diverse planting.
👉 Click here to see top options

• Sunflower Seed Starter Kit (Trays + Labels + Compost)
A complete beginner-friendly kit with everything you need to sow sunflower seeds indoors or in a cold frame before planting out.
👉 Click here to see top options

• Sunflower Support Stakes & Twine Set
Tall varieties often need support — this kit helps keep stems upright as they grow toward the sun.
👉 Click here to see top options

• Bird & Wildlife Sunflower Seed Mix
Also great for feeding wild birds later in the season or sowing separate patches to attract wildlife into your garden.
👉 Click here to see top options

• Grow Lights / Heat Mat (Optional for Early Sowing)
Boost germination and early growth if you’re starting seeds indoors before outdoor planting is warm enough.
👉 Click here to see top options

This guide explains the best time to grow sunflowers in the UK from start to finish.

🌻 Best Time of Year to Grow Sunflowers

In the UK, sunflowers are grown from spring through summer.

At a glance:

• March–April: start growing indoors
• Late April–May: grow outdoors from seed
• June–September: plants grow, flower, and set seed

Sunflowers need warmth, light, and frost-free conditions to thrive.

🌱 Growing Sunflowers Indoors

Best time: March to April

Starting sunflowers indoors allows you to begin growing earlier in the year.

Benefits include:

• Protection from frost
• Stronger early growth
• Ideal for giant sunflower varieties

Plants are usually grown indoors for a few weeks before being moved outside once the weather warms.

🌞 Growing Sunflowers Outdoors

Best time: Late April to May

Sunflowers can be grown directly outdoors when:

• The risk of frost has passed
• Soil temperatures have warmed

In colder areas of the UK, it’s safer to wait until mid–late May.

❄️ Can You Grow Sunflowers Too Early?

Yes. Growing sunflowers too early can cause:

• Poor germination
• Seed rot in cold, wet soil
• Frost damage to seedlings
• Weak or stunted plants

Sunflowers dislike cold conditions, so waiting for warmth is key.

🌡️ Ideal Conditions for Growing Sunflowers

Sunflowers grow best when:

• Soil temperature is above 10°C
• They receive full sun
• Soil drains well and isn’t waterlogged

Once conditions are right, growth is rapid.

🌻 How Long Sunflowers Take to Grow

From sowing to flowering, most sunflowers take:

• 10–14 weeks, depending on variety

Plants usually flower from mid-summer to early autumn.

🌼 Final Thoughts

The best time to grow sunflowers in the UK is spring, once temperatures rise and frost risk has passed. Start growing indoors in March or April, or grow outdoors from late April to May for the best results.

Good timing leads to stronger plants, taller stems, and bigger, brighter flowers.