How to Grow Sunflowers

Sunflowers are such a joy to have in the garden. Learn how to grow sunflowers from seed to brighten up your gardening space this year.

Sunflowers are, by far, one of my favorite flowers to grow. They’re low maintenance, germinate easily in the springtime, shoot up like a rocket, and put on a spectacular summertime show of bright, friendly blooms. Pollinators and birds love sunflowers, too, so they can be enjoyed by gardeners deep into autumn thanks to all of the creature activities. Let me help you learn how to grow sunflowers to add some extra happiness to your growing space.

Finding the Best Spot to Grow Sunflowers in Your Garden

Maximize their potential by planting them in an area that receives full sun for 6 to 8 hours each day. If you’re unsure of the best location for your sunflowers, you should do sun mapping to find that ideal space. You can find more information for how to do sun mapping in this post.

Once you’ve found the best space to grow your flowers, it will be time to get to know your soil. If the texture is sandy or full of clay, you will need to add compost to achieve a loamy texture.

Due to the size and shape of your full sun gardening space, determine what size of sunflowers you’re able to grow. Sunflowers have an incredible range of height depending on the variety. Consider the following:

Will you be able to stake tall sunflowers or attach them to a fence to help them stay in place?
Will tall sunflowers cast too much of a shadow on smaller garden plants?
Should shorter sunflowers be grown in front of the a garden border or in the middle?
Will the sunflowers have enough space to branch out?

How to Choose a Variety of Sunflowers to Grow

There are so many varieties from which to choose- there is a sunflower for everyone! Do some research and make some decisions on these four important things:

First, decide what size your garden can accommodate: dwarf sunflowers reach about 24 inches tall, mid-size sunflowers hover around 5 feet, and giant sunflowers can reach over 11 feet tall.
Note the length of time until the sunflowers reach maturity. Some varieties take longer than others to get to full bloom, so choose one that fits into your growing season.
Next, think about whether or not you’d like to collect the seeds for roasting or if you’d rather leave them for the wildlife.
Finally, decide what colors you’d like to see in your garden: golden yellow, white, ombre, maroon, red, orange, cream, plum, or white.

When to Plant Sunflower Seeds

The best time to plant sunflower seeds is on or after the average frost date for your growing zone. That being said, volunteer sunflowers pop up in my garden (zone 5B) a month before my last frost date and they usually have no problem surviving a light frost, so if a surprise frost does come, please don’t panic! Your seedlings should be just fine.

How to Plant Sunflower Seeds

Find the best location with ample sunlight (6-8 hours per day).
Make holes 1/2 to 1 inch deep and space them the proper distance apart. The spacing requirements should be noted on the seed packet of the variety you purchased. If it isn’t, check the seed company’s website for more information about your specific variety.
Plant your seeds and lightly cover with soil. Water them and keep them moist until they sprout.
After planting, add mulch around the hole (don’t cover it) to help the ground retain moisture and suppress weeds.

How to Care for Sunflowers As They Grow

Watering Sunflowers

Sunflowers prefer to receive about 1 inch of water per week (including rainfall totals.)

However, the larger varieties are capable of putting down roots that are more than 6 feet deep (!!!) and sunflowers as a whole are known to be pretty drought resistant. (Remember earlier how I said that one of the best things about them is that they’re low maintenance?)

Staking Sunflower Stalks

I love planting biggest sunflowers I can find just to see how fast (and how tall) they’ll grow. Certain sunflower varieties grow up to 2” a day! However, the bigger they get, the better the chance of them getting knocked over thanks to high winds.

Consider planting the biggest varieties close to a fence or structure that they can be staked to prevent tipping. If no fence or structure is nearby, drive some strong garden stakes (steel fence posts work best) into the soil when you plant your seeds.

Tips for Cutting Sunflowers

Best Time to Cut Sunflowers for a Vase

The best time to cut sunflowers for a vase is on a dry day in the early morning. For the longest lasting display, choose flowers that have just begun to open.

How to Cut Sunflower Stems

Cut the stem of the flower at a 45° angle at the desired height. Immediately put it into a bucket or the prepared vase that has been filled with room-temperature water. Do not let the base of the stem dry out.

close up of sunflowers in vase — Photo by Patrick Nizan on Pexels.com

Caring for Sunflowers in a Vase

Let’s keep those flowers from wilting, shall we?

Change the water at least every other day. Make sure the water is room-temperature.
Add 1 teaspoon of sugar and 2 tablespoons of lemon juice to the water to give the sunflowers a boost.
Keep the vase of flowers away from drafts and out of direct sunlight.

What to Do with Sunflowers When They’re Done Blooming

If you don’t mind the unfortunate look of spent sunflowers, you could leave them up well into the fall season so pollinators and birds can enjoy every last bit of goodness from the plants. When you’re ready, cut them down at the base.

If you live in an area where you can get yard waste taken away for free, follow the instructions from your city (or whomever) and dispose of the stalks that way. If you don’t live in an area with yard waste pick-up (and if it’s realistic for your backyard space,) put the stalks in a pile and let the stems dry out over the winter. In the spring after the littlest creatures have emerged from their winter hiding spots (your sunflower pile being one of them,) properly dispose of or burn the spent stalks.

FAQ

Do sunflowers come back every year?

Most sunflowers are annuals, but most sunflowers self-seed. If you let the sunflower heads dry on the stalk after they’re done blooming, birds and other creatures will be all over them. That means they’ll be dropping seeds and you’ll be enjoying volunteer sunflowers next season.

How long will sunflowers last in a vase?

Sunflowers will last about a week in a vase if kept under perfect conditions (see tips above.)

Do sunflowers bloom all summer?

Each sunflower head will last two to three weeks depending on the weather and conditions in your garden.

How many sunflower seeds to plant per hole?

In ideal conditions, sunflowers germinate very well and do so quickly. Under ideal conditions it is only necessary to plant one seed per hole.

What not to plant with sunflowers?

Do not plant medium height to tall sunflowers near any plants that you want to receive full sun. Plant those taller sunflower varieties on the north side of your garden so they will not cast a shadow over other plants as the sun moves across the sky throughout the day. In addition, avoid planting vegetables that will compete for light or growing space near sunflowers- such as root vegetables, tubers, cruciferous vegetables, tomatoes, and peppers.

Do sunflowers need a lot of water?

Including rainfall, sunflowers need about 1 inch of water each week.

Confession: I only water my sunflowers when they’re in their seedling stages to help set them up for growing success- that goes for dwarf varieties as well as the giants. Some varieties can produce roots that can grow up to 6 feet deep, so they have no issue reaching water on their own if I focus on my gardens that are designated to food production.

What happens if sunflowers are planted too close together?

Each plant will compete for nutrients in the soil. Stick with the ideal spacing requirements when you’re planting (noted on the seed packet) and the sunflowers will form a beautiful border or hedge for the summer and fall.