How to Grow Sunflowers from Seed : A practical Guide from Seeds to Flowers

Sunflowers are one of the most rewarding flowers to grow from seed. They’re quick to get going, easy enough for beginners and available in everything from compact varieties for pots to towering giants several metres tall. There are also many colours and multiheaded varieties available.

Give them plenty of sunshine, keep young plants protected from slugs and snails, and water regularly while they establish. With a little care, you’ll have impressive flowers from summer into early autumn.

When to Sow Sunflower Seeds

Sow indoors: March to April
Sow outdoors: April to May
Plant out: May to June
Flowering: July to October

Sunflowers are tender when young, so avoid planting them outside too early. If you start seeds indoors, wait until the risk of hard frost has passed before moving plants permanently into the garden.

Where to Grow Sunflowers

Choose a warm, sunny position where plants will receive plenty of direct sunlight.

Sunflowers grow best in reasonably fertile, well-drained soil. Taller varieties appreciate a position sheltered from strong winds, as their large leaves and flower heads can make mature plants quite top-heavy.

Compact varieties are excellent for containers and smaller gardens.

Sowing Sunflowers Indoors

Starting sunflowers indoors gives young plants a useful head start.

Sow individual seeds about 1–2cm deep in small pots filled with seed or multipurpose compost. Water gently and place somewhere warm and bright.

Keep the compost slightly moist but not waterlogged.

Seedlings usually develop quickly. Once they are growing strongly, gradually acclimatise them to outdoor conditions before planting them into their final position.

Sowing Sunflowers Outdoors

Sunflowers can also be sown directly where you want them to flower.

Wait until the soil has begun to warm in spring and the danger of severe frost has passed. Prepare the soil, remove weeds and sow seeds about 1–2cm deep.

Water after sowing and keep the area moist while the seedlings establish.

Young sunflower seedlings are particularly attractive to slugs and snails, so keep an eye on them.

Planting Out Sunflowers

Plant indoor-raised sunflowers outside once the risk of hard frost has passed.

Water the plants before planting and try not to disturb the roots unnecessarily.

Spacing depends heavily on the variety. Compact sunflowers can be planted relatively close together, while giant and strongly branching varieties need considerably more room.

As a general guide:

• Compact varieties: around 20–30cm apart
• Medium varieties: around 30–45cm apart
• Tall or branching varieties: around 45–60cm apart

Always check the individual seed packet because sunflower varieties vary enormously in size.

Growing Sunflowers in Containers

Compact sunflowers are very good container plants.

Choose a reasonably large pot with drainage holes and fill it with good-quality multipurpose compost. Avoid overcrowding the plants.

Containers dry out considerably faster than garden soil, so check them regularly during warm weather.

Dwarf varieties such as Teddy Bear are particularly well suited to pots because they give you the cheerful sunflower look without needing the space or support of a giant variety.

Watering Sunflowers

Water young plants regularly while they establish.

Once growing strongly, sunflowers develop substantial root systems, but they will still benefit from a thorough watering during prolonged dry periods—particularly as flower buds are developing.

Container-grown sunflowers need more frequent watering.

Try to water the soil around the base of the plant rather than repeatedly wetting the foliage.

Feeding Sunflowers

Sunflowers growing in reasonably fertile garden soil usually need little additional feeding.

Very tall varieties, plants growing in poorer soil and container-grown sunflowers can benefit from occasional feeding during active growth.

Avoid excessive feeding, particularly with high-nitrogen fertilisers, as this can encourage lots of leafy growth at the expense of flowers.

Supporting Tall Sunflowers

Compact varieties generally need no support.

Tall and giant sunflowers may need staking, particularly in exposed gardens.

Put a sturdy cane or stake alongside the plant and loosely tie the stem to it as the sunflower grows. Don't tie it too tightly—the stem needs room to thicken.

It is much easier to provide support before a tall sunflower starts leaning than to rescue one after strong wind has damaged it.

Encouraging More Flowers

Some sunflowers naturally produce one enormous main flower, while branching varieties produce numerous smaller blooms.

If you want lots of flowers for cutting, choose a branching variety rather than trying to change the natural habit of a giant single-stem sunflower.

Removing faded flowers from branching varieties can also help keep the plants looking tidy and encourage remaining buds to develop.

Growing Sunflowers for Cut Flowers

Sunflowers make superb cut flowers.

Choose varieties bred for branching or flower production if cutting is your main aim. Cut stems when the flowers are beginning to open rather than waiting until they are fully mature.

Cut early in the morning when possible and place the stems into water promptly.

Regular cutting from branching varieties can provide flowers over a surprisingly long period.

Common Problems

Slugs and snails are probably the biggest threat to young sunflower plants. Protect seedlings until they are large enough to withstand some damage.

Wind damage can affect tall varieties. Grow them somewhere reasonably sheltered and provide support where necessary.

Dry conditions can cause plants to struggle, particularly in containers. Water thoroughly rather than giving plants frequent tiny amounts.

Poor flowering can result from insufficient sunlight, overcrowding or excessively rich feeding that encourages leafy growth.

After Flowering

You don't necessarily need to remove sunflower heads as soon as the petals fade.

If left on the plant, mature seed heads can provide a valuable food source for garden birds. Sunflower seeds are edible.

Alternatively, allow the heads to mature and dry before collecting seed.

Bear in mind that seed saved from hybrid varieties may not produce plants identical to the parent.

Our Sunflower Growing Tips

Give them as much sunshine as you can.
Sunflowers really do live up to their name. A bright, sunny position generally produces stronger plants and better flowers.

Protect them while they're small.
A sunflower can eventually become enormous, but a tiny seedling can disappear overnight thanks to a hungry slug.

Choose the variety for the space you have.
You don't need a huge garden to grow sunflowers. Compact varieties are brilliant in pots, while giant varieties are great fun where you have the room.

Support tall plants early.
If you're growing one of the giants, adding a stake before the plant needs it is far easier than trying to straighten it after a windy night.

Let a few seed heads stay.
Once flowering is over, leaving some mature heads for the birds is an easy way to make sunflowers useful to wildlife as well as beautiful.