How To Grow Sunflowers

With their large blooms and bright, happy colours, nothing screams summer like sunflowers! Some of these fascinating flowers can grow up to 5m tall, though there are plenty of dwarf varieties to suit small gardens and container growing.

In this guide, we’ll explore how to grow sunflowers at home, covering everything from when to plant sunflower seeds, to how to harvest sunflower seeds, and everything in between. We’ll also take a look at some of the most popular sunflower varieties available and where to buy them.

Sunflower seeds grow best in full sun (at least 6-8 hours per day) in a spot sheltered from strong winds – along a fence or near a building is ideal. If your site is particularly windy or your plant becomes top-heavy, it will require staking.

Tall sunflower varieties have long tap roots that need plenty of soil depth to stretch out. To help them, ensure your soil is well-dug, a strong garden fork is our tool of choice to prepare the soil. Start by loosening the soil across and then down to a depth of about 60cm, removing any rocks or competing roots.

Sunflowers are heavy feeders, so the soil needs to be nutrient-rich with organic matter or composted manure. Alternatively, you can add a sprinkling of slow-release fertiliser if you prefer. Dwarf sunflower varieties will happily grow in pots placed in a sunny position, too. Simply fill your pot with a quality potting mix that is well-draining and has some added nutrition.

When to Sow Sunflower Seeds

Sunflowers can flower in as little as 8 weeks from sowing, but some may take up to 12 weeks to mature. Your seed packet will outline how long your variety takes. Sow your sunflower seeds when the soil is warm, at least 21°C, too cool a soil and your seeds may struggle to germinate.

How to Sow Sunflower Seeds

It’s best to sow sunflower seeds directly into the soil when the danger of frost has passed. Transplanting sunflowers can damage their tap root and will set back their growth. If you need to start in pots, try a compostable one so it can be planted pot and all, eliminating the risk of transplant shock.

Give plants plenty of room, especially for low-growing varieties that will branch out. Stagger plantings over 5 to 6 weeks to enjoy continuous blooms or pick varieties that grow multiple heads, such as Solar Flash F1 or Lemon Striker F1.

Protect young seedlings from pests by placing a mesh cover over your sowing site or using some slug and snail pellets. Once the plants are large enough, they will resist these attacks.

While the sunflower plant is small, water it regularly around the roots. Once established, water it more deeply and infrequently to encourage deep-root development. You can also add a liquid feed to your watering every couple of weeks to give plants an extra boost. A top tip here is to use a feed that has a good amount of potassium for flower development and keep any liquid feeds directly off the stem to prevent rotting.

Tall sunflower species will require support, so tie the plant to a stake as it grows. We like to use strips of old t-shirts or stockings to secure the sunflower. This will ensure the stem isn’t damaged.

Sunflowers make great cut flowers, or if left to produce seeds, they will attract birds to your garden. If you want to harvest sunflower seeds for snacks, protect the flower heads with netting before the birds find them.

Let the flower head turn brown and dry off before harvesting the mature seeds. Single-flower varieties are often best for this purpose. Note that pollen-free sunflowers will not produce mature/edible sunflower seeds.