A Guide to Planting Sunflowers

Nothing says summer quite like sunflowers. With their joyful and vibrant petals, sunflowers bring a splash of color to any garden. While golden yellow petals are most common, there are different variations of sunflower, from red and deep purple, to white. Sunflowers are well-loved by experienced gardeners and novices alike and are a great flower for children to grow and take care of. 

Sunflowers can be planted and grown at home by following a few simple steps. With the right care and patience, standard sunflowers usually grow from 6 to 10 feet tall, while giant varieties can grow as high as 20 feet. 

Here, we cover how to plant sunflowers so you can grow impressive and eye-catching blooms in your garden.

When to plant sunflowers

Choosing the right time of year to grow sunflowers is essential to ensure your blooms grow their best and to avoid rotting. The best time to plant your sunflower seeds is in the spring, usually from early March to mid-May - but make sure to check the seed packet beforehand.

To give your seeds the best start, they will need to be protected until they have germinated and seedlings have grown to around 2 inches. It may be best to grow them indoors until this point, to avoid any damage to them from the cold weather.

How to plant sunflowers - step by step

Planting sunflowers from seed should be a straightforward process and can be a fun activity to do with children. To make planting sunflowers feel as simple as possible, we’ve broken it down step by step below.

Step 1: Prep

Before you plant your sunflower seeds, you will need to make sure you have everything you need to grow them successfully. 

Sunflowers need a sunny but sheltered spot and good, rich soil (as well as well-rotted manure, or garden compost if you have any). Before you buy your seeds, you’ll need to choose the variety of sunflower you’d like to plant carefully. Do you want your sunflowers to grow as high as 15 feet, or would you prefer smaller plants? Dwarf sunflowers only grow around 3 feet tall, which are perfect for smaller spaces such as garden planters or boxes. 

Step 2: Depth

Sow the seeds into individual pots or seed trays of multi-purpose compost about 1 inch deep and 3 inches apart from each other. For tall sunflowers, or those that grow into multi-branched bushes, you should sow the seeds 3 feet apart from each other. 

Step 3: Flower food

Once your seedlings have germinated and grown to around 2 inches, they can be moved into individual, larger pots, around 3 inches in diameter. Add a small amount of multi-purpose compost to each pot, then carefully remove the seedling from its previous seed tray or pot and place it gently into the new pot. Then fill the pot with more compost and gently push the compost down to compact it. Water each pot well, before positioning them in a warm and bright spot. 

Once you’ve done this, you can start to use a liquid fertilizer on the plants to help support the seedlings’ growth. Granular fertilizer is a good choice for planting sunflowers in the spring, due to a slow release of nutrients over time. Once the sunflowers have become more mature, you can use a water-soluble fertilizer.

Step 4: Plant out

Once your sunflowers have germinated, make sure to keep them well-watered until they are ready to be planted in the garden. Prepare the soil by removing any weeds and plant your sunflowers at the same depth they were in their pot, in a sunny but sheltered position like the back of a flower border.

Soil requirements

To help your sunflowers grow healthy and vibrant, plant them in fertile, well-drained soil. While mulching sunflowers isn’t always necessary, if you live in a dry climate you may choose to do so. To mulch the roots, apply a 2-4 inch layer of straw or bark mulch, while leaving a ring of bare soil around the stalk. This will make sure the mulch doesn’t make contact with the plant, and it will preserve soil moisture and prevent weeds.

Planting sunflowers in different environments

Provided you take care of them well, sunflowers can be planted and will thrive in most US states, looking their best in the summer months. This is because sunflowers are full-sun plants and only thrive in environments where they receive 6 or more hours of direct sunlight per day. 

They are known to survive extreme heat as long as their moisture needs are met, so make for great blooms in hotter states like California and Arizona. Provided your flowers have well-drained soil and good air circulation to prevent root rot, they should tolerate high temperatures. 

Do you live in a cooler climate? Sunflowers can also handle cooler environments as long as they receive plenty of sunlight every day. 

Understanding common pests and diseases

Pests

Bold and beautiful, sunflowers are a flower that everyone recognizes and loves, and that unfortunately includes pests! Thankfully, pests only tend to cause significant damage to sunflowers when in large numbers. Here are some of the most common sunflower pests to watch out for, to keep your blooms healthy and pest-free: 

• Cutworms: Cutworms love to chew on new sunflower seedlings and often feed at night, before hiding in the soil a few inches from the plant. To find them, dig the soil around the plant. You’ll tend to notice leaf damage that looks like small transparent sections chewed by the insects, or wilting. To prevent cutworms you can use weed control, as weeds shelter and feed them. Cutworms tend to live in the grass, so to prevent them from getting to your sunflowers, leave a three-foot-wide soil strip between your lawn and your plants.

• Sunflower beetles: Sunflower beetles are easily recognizable due to their red-brown head and cream-colored wings. While they’re attractive and unique insects, they can cause damage to your sunflowers by creating shotholes in the leaves when they feed. Thankfully, the number of sunflower beetles is limited by “beneficial insects” like ladybugs, who eat their eggs!
• Sunflower moths: Sunflower moths, who lay their eggs within the flowers, are one of the most destructive pests to sunflowers. Once the eggs have hatched, the insects move into the flower heads to feed, which can destroy the flower. To avoid sunflower moths, you can try a biological insecticide.  

Diseases

Sunflowers are quite hardy plants, so aren’t as affected by diseases as other flowers. But there are some diseases to watch out for to keep your blooms healthy and thriving. 

Fungal diseases like Alternaria leaf blight causes dark brown lesions on sunflower leaves, surrounded by a yellow halo. This can be treated by pruning out the infected leaves and leaving a good amount of space in between plants to reduce humidity and improve air circulation. 

The most common threat to sunflowers is stem rot, also known as white mold. This can cause sudden wilting leaves and root or head rot. Proper watering and crop rotation can help to reduce the chances of this disease affecting your blooms.

Companion plants for sunflowers

Sunflowers make great companion plants due to their height, which can help shelter other plants from the sun. Lettuce will grow well next to sunflowers, as it enjoys the shade, especially in the summer. Peppers can get damaged in hot temperatures, so will enjoy being shaded by tall sunflowers. Sunflowers also make for great pollinator attractors, due to being large, beautiful blooms that attract bees. The bees will then drift to other plants in your garden to pollinate them too.

Prefer to receive sunflowers in the mail? Order a stunning vase arrangement or bouquet from French Florist 

Maybe you’re not a gardener, or simply don’t have the space to grow sunflowers yourself. This shouldn’t stop you or your loved ones from being able to marvel at the joy and beauty that sunflowers bring. 

The local artists at French Florist can craft you a beautiful and personalized arrangement of sunflowers.  Order a beautiful sunflower arrangement for delivery nationwide, and same-day local delivery, to bring a smile to a loved one’s face, or even as a gift to yourself. Our local team of floral experts design every arrangement with care and attention, ensuring they pass strict quality control - so you know you’ll receive the very best blooms every time.