How to Grow Sunflowers: Planting + Care

Key Takeaways:

Table of Contents

7 Quick Tips for Growing Sunflowers
Choosing Your Sunflower Seed Varieties
How to Plant Sunflower Seeds
How to Germinate Sunflower Seeds
Fertilizer and Pest Control
How and When to Harvest Sunflowers

It is hard not to smile when you see a garden with a wall of sunflowers. They're simply the perfect addition to any outdoor space – flower or vegetable!

Not only are they stunning, but sunflowers are easy to grow, reasonably drought-hardy, pest-resistant, and inexpensive. They are also versatile and can be raised for their seeds, as a barrier device, or simply for aesthetics. They are, simply put, the perfect all-purpose flower!

Today we’ll be discussing plant care, growing tips, and harvesting best practices for this ornamental plant.

7 Quick Tips for Growing Sunflowers

Here are seven tips for growing sunflowers to help you get the most out of your garden.

Choose a full-sun location: Six to eight hours of sunlight per day is ideal for growing sunflowers.
Give your flowers space to grow: Plant seedlings at least 12 inches apart, as the sunflowers will spread out over time and grow best when they have plenty of room.
Add support: Wind can wreak havoc on a sunflower's blooms if they aren't given support from the start — either by staking them or tying them into place with twine or string.
Use fertilizer to maximize height: Sunflowers grow quickly and need nutrients to support their growth, and fertilizer allows them to reach their full potential size.
Water evenly during the growing season: Water regularly as the seedlings establish and as needed during the growing season to keep the soil moist but not soggy.
Include a windbreak: Sunflowers love the sun but can quickly get blown over when the wind picks up.
Place mulch down after planting: Mulch will help keep weeds from taking over the area around your sunflower plants and will also provide moisture.

Choosing Your Sunflower Seed Varieties

Without question, the most challenging part of growing sunflower seeds is deciding which variety to grow. Choosing the perfect sunflower variety can be a bit overwhelming as there are over seventy known varieties currently on the market.

The most popular categories of sunflower seeds include:

Varieties that grow along a single stalk and those that tend to shrub out.

Some varieties produce large seeds for eating and those that are better suited for admiring.

And don't forget, sunflowers don't just come in yellow! There are various flower colors including white, red, brown, purple, even green sunflowers!

Here at Harris Seeds, we pride ourselves on our vast collection of sunflower offerings with sixty-five different varieties available for purchase. Chances are, we have what you're looking for!

Consider Space Available

The biggest thing to take into consideration before planting is space. Do you have room for ten-foot-high stalks? If not, you'll probably want to steer clear of the Mammoth sunflower and stick with something a little closer to the ground.

Varieties like Mammoth and American Giant are the perfect addition to any country homestead with wide-open spaces for a sunflower patch.

Or, perhaps you have a smaller apartment terrace that needs just a little pop of color in a pot. The variety, Bert, is the perfect little guy for you with a mature plant height of just eighteen inches.

When planting sunflowers, plant spread and height should always be the first box you check. But make no mistake, there is a sunflower for everyone and every garden!

Consider Breeding Characteristics

Determining size doesn't only help with deciding whether or not you have the appropriate space for the sunflower variety you choose to plant, but it also helps you determine what a specific variety is bred for.

Generally speaking, the larger the variety, the less opulent it is. It also takes longer to grow varieties with ten to twelve-foot stalks meaning they will bloom later in the season. Larger sunflowers equal larger heads, and larger heads equal larger seeds.

Thus, larger varieties are generally grown for consumption, while smaller varieties that grow faster and bloom longer are more suitable for cut gardens, flower gardens and flower beds.

Because smaller varieties are bred more for looks, that is also where the wide range of colors and textures comes in as well. Larger varieties tend to be what you think of when you think 'sunflower' – great big brown middle with yellow petals.

But in smaller varieties, you'll find center-less frilly textures like the Goldy Double (pictured below - top left), no real petals at all like the SunFill Green (top right), whites and creams like Full Moon (bottom left) and Pro Cut White Night, or deep browns like Rouge Royale (bottom right).

So keep your goal in mind when selecting a variety as well. Are you planting for sustenance or style?

How to Plant Sunflower Seeds

Sunflowers do best direct sown. This means that you don't have to worry about starting them indoors and transplanting them later. Just plant your seeds directly in your pot, garden box, or pasture where you intend them to grow from the very beginning.

Transplanting your sunflowers won't hurt them as they have relatively sturdy root systems, but they do like to send their roots down deep to stay upright without being top-heavy. The larger your seedling gets in a small space, the more staking they will need to avoid breaking.

Often it can be difficult to properly harden off your starts before your seedlings become too large to handle. For this reason, when you sow sunflower seeds, it is best to direct sow for optimal root growth.

Planting Sunflower Seeds

How to Germinate Sunflower Seeds

Sunflowers begin to germinate when soil temperatures are somewhere between sixty and seventy degrees Fahrenheit. We recommend planting sunflower seeds after the danger of hard frost (below twenty-eight degrees Fahrenheit) has passed.

It's important to note that while most sunflower varieties are annuals, many will reseed themselves if left to the end of the season on their own, especially if there are critters around the planting site to help spread the seed.

We said planting sunflowers was easy, but did you know it was so easy that birds and squirrels could do it? Sunflower seeds have a hard outer shell that protects them from most environmental damage, which is why mild/spring frosts and cooler days won't bother them too much, and they can many times over-winter and reseed themselves.

However, tender young plants are very susceptible to a hard frost, so if you want to be guaranteed a successful harvest, it's best not to leave your planting to the birds in the fall and plant in late spring when temperatures are a little more consistent.

How Deep Should I Plant Sunflower Seeds?

Your seeds will require dark to germinate, so they must be planted at the appropriate depth.

For most sunflower varieties, that's somewhere between a half and three-quarters of an inch deep, but you should look up the depth specific to your variety just to be sure. Keep your seeds damp but not wet until you see signs of germination, and then taper off to a regular watering schedule.

How Much Should I Water Sunflower Seeds?

How often do you water sunflower seeds? Remember, many native sunflower varieties grow wild on dry, hot plains and mountainsides. They are incredibly resilient, and even the most tender varieties are pretty drought-hardy, so be sure not to overwater.

You will know your plants need more water if the leaves and head tend to droop and appear soft. Don't panic! They will perk up almost immediately with a quick watering.

Overwatering does far more damage (root rot, shallow roots, unstable stalks, withered blossoms) to sunflowers than underwatering will, so err on the side of caution.

Fertilizer and Pest Control

Unlike many flowers, sunflowers don't need much by way of fancy fertilizers or pest control methods. Because they are native to such harsh conditions, they can perform fairly well in even the poorest soils. An occasional application of a standard low-dose all-purpose fertilizer is more than adequate.

Sunflowers are a fantastic food source and attractant for many pollinators, so it's best to avoid any sort of pest control unless the problem appears to be out of hand. An aphid or earwig here or there is no match for the persistency of the sturdy sunflower and is usually not cause for alarm.

How and When to Harvest Sunflowers

Harvesting your sunflowers will depend on variety.

If you're growing large varieties to harvest and eat the seeds, you won't need to worry about cutting anything until the very, very end of the growing season. Wait until the heads hang heavy, the plant is browning and beginning to die, and the seeds in the center of the head have started to dry and fall.

Then all you have to do is simply cut the head from the stalk and set it somewhere out of the elements to fully cure before removing the seeds. At this point, you may roast the seeds for a longer shelf life or consume as-is.

If you're growing your sunflowers for cut bouquets, you will likely have to harvest throughout the season numerous times because sunflowers are annual.

The best way to do this is to harvest in the early morning when temps are still cool, and blossoms haven't fully opened just yet. Cut the blossom where it meets the main stem at a forty-five-degree angle. Strip the stem of all of the leaves and place in water immediately. Once your mainline stops producing new heads, you will know it is time to either pull your plant or leave it to reseed.

As you can see, whether it's planting, watering, harvesting sunflower seeds, or anything in between, these big bright flowers don't need to be fussed over. There is almost zero intimidation factor when it comes to growing sunflowers.

They're a whole lot of reward for very little work, and there are so many options with color and style that they make the perfect blossom for even the most novice of gardeners. This season, you must simply add sunflowers to your "to grow" list!

Frequently Asked Questions:

When should I plant sunflower seeds?

Direct sow after the risk of frost has passed. For a longer harvest, succession plant every 2 to 3 weeks.

How deep do I plant sunflower seeds?

Plant most sunflower seeds about 1 inch deep, unless the seed packet says otherwise.

How far apart should sunflowers be spaced?

Spacing depends on the variety and whether you want single stems or branching plants. Use closer spacing for single-stem cut flower production.

How do I keep sunflowers from falling over?

Choose the right variety for your site, avoid excess nitrogen, and provide support in windy areas. Adequate spacing and deep watering help roots anchor.