How Late Can You Plant Sunflower Seeds?

In your haste to grow everything under the sun this year in your garden (hi, have we met because that’s me), you may have forgotten about your fall flowers. You might be dreaming about the fall harvest, and now you’re wondering – is it too late to plant sunflower seeds? The answer is maybe not. It might not be too late, depending on the type, time of year, or how much time you have left in your growing season. We will walk you through determining if you can still plant sunflower seeds. We also have a list of short-season sunflowers you can grow if it is late into your growing season.

When should sunflowers be planted in the garden?

Generally speaking, the best time to plant sunflowers is when soil temperatures have risen to at least 50F or two weeks after the last frost in your area. Planting in late spring will provide blooms from mid-summer to early fall, depending on each type grown. 

These bright yellow blooms on large heads are the easiest flowers to grow in the garden. And lucky for all of us, You can plant some short-season varieties late in the season.

Related: Do you love yellow flower petals as much as I do? We have an entire blog post dedicated to planting and growing yellow perennials!

How late can you plant sunflowers?

Is it too late to plant sunflower seeds?

Sunflowers take between 55 and 100 days between sowing and full bloom. As long as you have that many days or more between now and the first frost date in your region, you should be good to go to plant late-season sunflowers.  

Check the back of your sunflower seed packet to see how many days are needed for growing that particular type, or you can plant some of the varieties we list below. 

Not sure when your first average frost might occur? You can check this site to determine your region’s growing zone and the first and last frost days. 

Sunflower varieties for the short growing season

Dwarf sunflowers are the types of sunflowers that do best in a shorter growing season. Most dwarf types like “Firecracker” will bloom in 50-60 days. You could plant those flowers at the end of July for a stunning show at the end of September. 

If you are late in the season, try to avoid planting tall sunflowers like mammoth Russian; they will take too long to grow (70-90 days) and will likely not have enough time to bloom. That is unless you have a longer growing season. 

Here are some short-growing season sunflowers for you to consider: 

• Vincent’s Choice: 50-60 days
• Big Smile: 50-60 days
• Gold Rush 60-65 days
• Sunrich Summer Provence: 60-65 days
• Starburst: 60-65 days 
• Sunrich Gold: 60-70 days
• Double Quick Orange: 65 days
• Sunright Supreme: 60-70 days
• Sunrich Lime: 60-70 days
• Teddy Bear: 65-75 days  

Where to Plant Sunflowers

Sunflowers are hardworking garden plants that do well in the back of borders, used as annual hedges, in a children’s garden, and, of course, in the cut flower garden.

Tall sunflower varieties can even be planted as a windbreak.

Planting and propagation of Sunflowers

There are two ways to plant sunflowers in the garden: starting seeds early indoors or directly sowing. Both methods work, and early blooms are the only advantage to starting plants indoors.

How to plant sunflowers

• How to start seedlings indoors: To get a head start on the season, you can sow sunflower seeds indoors in early spring, 4 to 6 weeks before the last frost day in your region. Plant seeds in seed trays under grow lights. You can also sow seeds directly outdoors after the last frost date.
• How to Direct Sow: Sow seeds to a depth of 1/2 – 1 inch and space seeds (or young seedlings) 2-3 feet apart. Sunflower seedlings started indoors will transplant well if you do not disturb their roots. It’s a good idea to stake taller sunflower varieties to protect them from high winds.

How to propagate Sunflowers:

• Seeds: When the flower dies back and the seeds ripen, they are easily removed to store for planting next year.
• Cuttings: You can also propagate sunflowers from cuttings.

Learn More: How to Harvest Seeds for Next Year’s Growing Season.

Caring For Sunflowers

Sunflowers are native North American plants grown for their large flower heads. Annual sunflowers (Helianthus annuus) provide edible seeds for wildlife and the gardener. These flowers are easy to care for so long as their needs are met:

• Sun Requirements: For best results, plant in full sun.
• Soil requirements: Sandy well-draining soil with lots of organic matter.
• Water Requirements: Ensure your sunflowers receive at least 1 to 1-1/2 inches of water each week. Young plants will require less until they are more established.
• Feeding Requirements: A spring application of compost or general-purpose fertilizer will be adequate. You can give supplemental feedings through the growing season with a foliar spray or monthly side dressing for extra showy blooms.

Learn More: A Guide For Growing Sunflowers

Common insects that attack Sunflowers and how to Deal with them

Sunflowers can generally handle most insect attacks, but if they get out of hand, insect pests can cause damage.

Aphids

Plants infected with aphids will have strange and distorted growth that can be curled or puckered. Leaves may turn yellow or brown, and these insects can heavily damage flowers. Plants may also wilt under bright sunlight.

You can manage light aphid infestations by washing the flowers with a strong spray from the hose. For heavier infestations, use insecticidal soap every 3-5 days for three weeks.

True Bugs

I never knew such a thing as “true bugs” until I started gardening. True bugs can cause deformed and stunted growth with tiny yellow or brown spots.

True bugs are pests like harlequin bugs, leaf-footed bugs, and tarshisned plant bugs, and they all can infest sunflowers.

Preventative measures are best at controlling true bugs. Keeping the garden clean from debris should be enough to help prevent any infestations from these bugs. Handpicking adults off the flowers and dropping them into a jar of soapy water is also a suitable control method.

Sunflower Moth

If your sunflower centers have webs and frass, you may have sunflower moths. The adults of this pest are a gray month that lays its eggs in the florets that make up the sunflower head.

Take preventative measures to control these moths because severe infestations will destroy the seed heads.

Spraying Bt when the flowers first appear is a suitable control method, as is handpicking the adults from the flowers to prevent them from laying seeds.

Most Common Diseases of Sunflowers and How to Treat Them

Several types of diseases will impact the growth of sunflowers :

Rust

If your sunflowers have powdery brown spots on the underside of the leaves, you may have rust. Severely infected sunflowers may be deformed.

Remove infected plants as soon as possible and destroy diseased plants. Clean up the garden and destroy all plant material at the end of the season to avoid reinfecting the garden next year.

You can prevent rust by applying wettable sulfur weeks before rust typically appears. Be sure to space plants adequately so there is enough room for air circulation.

Wilt and Stem Rot

If your sunflowers suddenly, without reason, begin to wilt and leaves turn yellow or develop a mottled pattern, you may have stem rot.

Stem rot will present with thick-felt light growth on the stems. Stem rot usually develops after a stretch of wet weather.

Preventative measures are the best way to control stem rot. First, be sure the garden is clean and find the right spot where sunflowers will have good draining soil.

Sunflower uses

Sunflowers have so many uses in the garden –

• Sunflowers make excellent cut flowers.
• The sunflower heads also make great dried flowers for display.
• They are a food source for birds, bees, and wildlife. The seed head becomes a natural bird feeder in late summer and early fall.
• You can harvest seeds! Sunflowers produce edible seeds that can be roasted to create a tasty healthy snack.
• The plant’s long tap roots help break up and aerate the soil.
• Sunflowers make excellent companion plants for corn, tomatoes, squash, and more.
• Also known as hyper-accumulators, sunflowers can absorb zinc, copper, and other common pollutants.  
• The flowers also grow so fast they choke out weeds, making them excellent for weed control.

Planting Sunflowers Indoors

Growing sunflowers indoors can be a rewarding and fun gardening project, allowing you to enjoy these vibrant blooms even if you don’t have a garden or outdoor space. The great thing about planting indoors is you can start them any time of the year, so long as you have enough sunlight to support growth!

Follow these steps to successfully grow sunflowers indoors:

1. Choose the Right Sunflower Variety:

• Select a sunflower variety that is suitable for indoor growing. Smaller and dwarf varieties, such as the “Sunflower Teddy Bear” or “Sunflower Dwarf Sunspot,” are ideal for indoor cultivation as they don’t grow as tall as their outdoor counterparts.

2. Gather Your Supplies:

• You’ll need the following items:
  • Sunflower seeds of your chosen variety
  • Small pots or containers (6-8 inches in diameter)
  • High-quality potting soil
  • A sunny windowsill or grow lights
  • Watering can or spray bottle
  • Fertilizer (optional)

3. Planting Sunflower Seeds:

• Fill your pots or containers with potting soil, leaving about an inch of space at the top.
• Plant sunflower seeds about 1 inch deep in the soil, following the spacing instructions on the seed packet. Usually, you can plant multiple seeds in a single pot.
• Water the soil thoroughly after planting, ensuring it’s evenly moist but not waterlogged.

4. Provide Adequate Light:

• Sunflowers thrive in full sun, so place your pots in a sunny location. A south-facing windowsill is often ideal for providing sufficient sunlight. Alternatively, you can use grow lights if natural sunlight is limited.

5. Maintain Proper Temperature and Humidity:

• Sunflowers prefer temperatures between 70°F to 78°F (21°C to 26°C). Keep your indoor environment within this range for optimal growth.
• Maintain a moderate humidity level by misting the plants regularly with a spray bottle.

6. Watering:

• Keep the soil consistently moist, but avoid overwatering, which can lead to root rot. Water when the top inch of soil feels dry to the touch.
• Avoid splashing water directly onto the sunflower foliage to prevent fungal issues.

7. Pruning and Thinning:

• As your sunflowers grow, thin them out by removing weaker seedlings to give the stronger ones more space to thrive.
• Pinch or trim the top of the main stem when your sunflowers reach a height of around 6 inches. This encourages bushier growth.

8. Support and Staking:

• If your sunflowers start to lean or become top-heavy, provide support by gently staking them with bamboo sticks or other support structures.

9. Fertilizing (optional):

• Sunflowers generally don’t require a lot of fertilization, but you can feed them with a balanced liquid fertilizer diluted to half strength every 2-3 weeks during the growing season.

10. Blooming and Maintenance:

• With proper care, your indoor sunflowers should bloom within a few months. Enjoy their beautiful, vibrant flowers.
• Deadhead (remove spent flowers) to encourage continuous blooming and prevent seed formation.

Remember that indoor sunflowers won’t grow as large as their outdoor counterparts, but with care and attention, you can still enjoy their cheerful blooms and brighten your indoor space.

It’s probably not too late to plant sunflowers

So, how late can you plant sunflower seeds?

With varieties that only require a 50-60-day growing season, you should be able to plant sunflowers as late as July for fall flowers.

If you live in a warm climate where the first frost comes well into late fall, you can plant sunflowers even later in the season.

Be sure to choose the right variety for the time you still have left, and follow our growing tips to ensure your sunflowers look marvelous come harvest season.

Looking For More Gardening Inspiration

Check out our other guides to growing sunflowers:

• Guide to Fertilizing Sunflower Plants
• All About Sunflower Growth Stages
• Top Dwarf Sunflower Varieties

We also have lots of flower gardening articles that you find inspirational:

• Planting Cosmos Flowers – How to Plant, Grow, and Care For Cosmos
• How to Grow Snapdragons from Seed to Glorious Displays of Flowers
• Impatiens Care – How to Grow An Abundance of Flowers in the Shade!
• How to Plant Calla Lily Bulbs
• How to Plant Gladiolus Bulbs For Beautiful Summer Blooms
• How to Plant Peony Roots in Spring (You can!)