If you love sunflowers as much as we do, you'll need the ultimate sunflower care guide to keep your plants healthy.
Sunflowers are a great addition to the garden because they’re colorful and have a distinct appearance that will stand out from the rest of your garden.
Their appearance isn’t the only reason you should grow them—they can also be a food source! You can roast the seeds and even grill the sunflower head and eat it like corn on the cob.
Sunflowers are easy to care for so they’re a great addition to any garden. Beginners can rejoice over their success, and seasoned gardeners can almost ignore this easy plant while they tend to more troublesome plants.
Let’s take a look at how to care for sunflowers so you can get them growing in your garden.
Types of Sunflowers
There are 20+ types of sunflowers. Sunflowers are native to North America and Mexico and are classified under the scientific name Helianthus. Helianthus annuus is the most common sunflower and has over fifty cultivars that range in color and appearance.
1. Annual vs. Perennial
Annual and perennial sunflowers have some similarities, but for the most part, they’re significantly different and will affect how they grow in your garden.
Annuals are usually taller, although there are some exceptions, and have one thick stalk with smaller branches. They also have one thick, long taproot.
It completes its entire lifecycle in one season and won’t come back the following year unless it drops seeds. Perennials are typically shorter and have several small stems.
They have small root systems with rhizomes and will die back in the winter but will return the following spring. If given the right growing conditions, they can spread and become weedy as they take over an area.
Dwarf sunflowers are usually no taller than 4 feet (1.2 meters). They’re typically perennials and can be grown in containers or the ground.
Standard sunflowers are 4-10 feet (1.2-3 meters) tall. They can be annual or perennial and are best suited for growing in the ground. However, large pots should be able to accommodate these sizes.
Giant sunflowers can reach over 10 feet (3 meters) tall. Depending on the variety and growing conditions, some can reach up to 20 feet (6 meters) tall! The world’s tallest sunflower to date grew to be 30 feet (9 meters) tall.
Tall varieties can only grow in the ground, and the ones that grow to be super tall may need extra support.
Yellow is the most common color, but it’s not the only option available! The development of cultivars has allowed there to be sunflowers in shades of brown, maroon, red, pink, orange, yellow, and white.
Many cultivars are striped or mottled and contain multiple colors.
Basic Sunflower Care Requirements
Before you can grow sunflowers, you need to make sure you can provide the flowers in the right conditions. Sunflowers are easy to grow if they have everything they need; otherwise, you may have a difficult time trying to keep them alive.
1. Sunlight and Temperature
They’re called sunflowers for a reason—they need sun and lots of it! Sunflowers should have full sun, at least six hours of direct sunlight every day. The more, the merrier, so you should try to plant them where they’ll have access to the most light.
Tall varieties can cause the surrounding area to be shady, making it harder for other full sun plants to get the light they need, so take this into consideration when choosing a location.
Most sunflowers can survive in USDA hardiness zones 2-11.
Sunflowers are heavy feeders, which means they need plenty of nutrients, especially if you’re growing a giant variety. The soil should be rich in organic matter or at least be treated with fertilizer periodically throughout the growing season.
They prefer alkaline soil with a pH of 6.0-7.5.
Sunflowers look their best when they receive enough water, but they’re drought-tolerant and love the sun, which is what makes them so easy to grow.
Ideally, they should receive an inch of water per week, and only the top half-inch of soil (1.27 centimeters) should dry out before you water again. The sunflowers can acclimate quite well if you have to let them get a little drier.
Try to water during the hottest parts of summer for the best results.
How to Grow Sunflowers
Now that you know the basic sunflower care details let’s get into how to care for them.
Sunflowers grow best when their root systems are left undisturbed. Direct sowing outside will minimize the risk of disturbing the roots. Transplanting causes disturbance and can be difficult for the little seedlings to acclimate.
The best time to plant seeds outside is after the danger of frost is gone.
If you live in a cold climate with a short growing season, you can plant seeds one or two weeks before the last frost since the seeds should be able to endure cold temperatures for a short time.
To sow outdoors, create small trenches about 1 inch (2.5 centimeters) deep and place a seed every 6 inches (15 centimeters). Keep the soil moist until you see little sprouts.
If you choose to start seeds indoors, the planting directions aren’t much different. You can begin a couple of weeks before the last frost and get a head start.
Plant a seed about one inch into the soil, cover it and keep the soil moist. The seed should be kept under a grow light for six to twelve hours. The longer, the better.
If you sowed the seeds outdoors, you can remove every other seedling to thin them out to 1-2 feet apart once the sprouts are a few inches tall and have developed their second set of leaves.
This same stage is when you can move your indoor starts outdoors as long as there isn’t any danger of frost. If you began the seeds before the last frost, keep them indoors until you’re certain the temperatures won’t drop below freezing again.
Seedlings are fragile and can’t tolerate drought as a mature sunflower can. Stay on top of watering and water once the top half-inch of the soil is dry.
Spring temperatures may allow the soil to stay moist for longer and you may receive enough rain not to have to water by hand, but don’t get too comfortable! You’ll still need to check to make sure the soil isn’t drying out.
Once the sunflowers are several feet tall, you won’t have to water them as much. Now they have strong root systems and have developed drought tolerance.
Annuals use their deep taproot to find water underground and perennials have rhizomes to store water. (Seedlings aren’t drought tolerant because they haven’t developed their sturdy root systems yet.)
Aside from watering, you won’t have much to do besides pest control, which we’ll look at in the next section. If you choose to fertilize your sunflowers during this stage, choose fertilizers that are low in nitrogen.
Nitrogen encourages foliage growth and will prolong the flower head from forming.
4. End of The Life Cycle
A sunflower is at the end of its life when all the leaves start to die. It’s normal for the bottom leaves to die as the flower grows taller, so you don’t have to be too worried.
Once you notice the middle and top leaves dying, that’s how you know the flower is nearing the end of its life cycle. You’ll also notice flower petals wilting and falling off, and the seeds in the seed head will be fully developed.
Now is the time to harvest seeds if you planted a variety that’s suitable for eating. You need to act fast because sunflowers attract birds and they’ll try to beat you to the seeds!
You can cut off the top foot of the sunflower and hang it upside down in a cool, dry place with a paper bag tied around the head to catch the seeds. There are other ways to do this, but this one is easy to do.
You’ll want to cut down the thick stalks of the annual varieties since they look a bit unsightly after the beautiful flower head and foliage have come and gone. Remember, annuals won’t come back, so you can remove the roots, too.
Annuals are tough to get out of the ground, so you may need a shovel to dig it out. If you have other flowers planted nearby, you may want to trim the stalk and wait for the other flowers to die before you try to remove the root system.
Common Problems When Dealing with Sunflower Care
Sunflowers are unfortunately not immune to diseases and pests. They can be the hosts of many problems depending on problems in the area and the climate.
Downy mildew is a fungal disease that looks white and has a somewhat web-like appearance. Mature sunflowers will have wilted leaves and seedlings will die.
Infected weeds and humidity can cause it. Other fungal diseases are rust and Alternaria leaf spot. Rust will create reddish-brown spots, and Alternaria has dark brown or black spots with pale yellow areas near them.
These diseases don’t have a cure, but they can be prevented by using fungicides before you spot problems. Avoid planting sunflowers in the same area for more than three or four years, as some diseases can stay in the soil and infect future crops.
The banded sunflower moth is an annoying pest that can target any sunflower in almost any growing region. The larvae are pink, red, or green and the adult moth has tan and dark brown stripes.
Eggs are laid in the seed head, and the larvae eat away at the seeds. You may notice the larvae if you spot webs on the flower heads. You can try to prevent this problem by planting a few weeks later than usual so you can try to miss their egg-laying season.
Once they’ve infected your flowers, you can use insecticides or Bacillus thuringenesis (BT) to kill them. Cutworms may be a threat to young seedlings or to root systems.
Cutworms live in the soil and feast on seedlings. Pay close attention to your seedlings to spot the problems. You can use insecticides to control them.
Sunflowers can attract different kinds of moths and beetles. As with other pests, BT and insecticides should be enough to eliminate them. BT is an organic option that’s safer for the environment, so you may want to use those.
Sunflowers also attract many bees, so try to choose insecticides that will keep beneficial pollinators safe.