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When to Plant Sunflowers

Elegant and majestic, sunflowers are a favorite for all sorts of landscaping and decor.

If you’re growing these ethereal beauties yourself, you want to enjoy them as best as you can, for as long as possible. That starts by knowing when to plant sunflowers so that you can get the most enjoyment out of them.

Read on to learn all about where and when to plant sunflowers, how to optimize their care, and so much more.

A field of sunflowers.

Deciding Where to Plant Sunflowers

Before you get moving on when to plant sunflowers, you need to pick the right spot for where to plant them! Sunflowers have a few optimal growing conditions that are just as key for their growth as the timing.

First and foremost, you want to pick a place to plant sunflowers where they have direct sunlight. These flowers absolutely thrive on unadulterated sunshine, so you want to plant them where they will receive 6 to 8 hours of direct sunlight every day.

A field of sunflowers.

If you are growing one of the giant sunflower varieties, you will also need to consider planting them alongside some type of vertical shelter or fence, as this will help protect them from the wind. Giant sunflowers can often be broken or thrown down by a strong gust of summer wind.

If you’re undecided about what specific sunflower to grow, browse the sunflower seeds selection available at one of our favorite seed retailers, Hoss Tools. We bet you’ll find a few varieties that will look great in your garden!

Next, you need to ensure the soil is well prepared. Sunflowers need soil that is loose and drains well, with a pH level of around 6.0 to 7.5. This will nurture their long taproots, which will plunge several feet down into the soil.

To keep your sunflowers healthy and well-fed, you’ll want to compost the soil or otherwise mix it with organic matter. This will keep your sunflowers happy and is a process that should be repeated throughout the flower’s life cycle.

Deciding When to Plant Sunflowers

Joker Sunflower

Direct Sowing vs. Transplanting

To start off learning when to plant sunflowers, you must first decide if you will want to direct sow them in the soil or begin them indoors.

Overall, sunflower plants do their very best when sown directly into the soil. However, the timing for when to plant sunflower seeds will vary greatly in different regions, since the seeds are highly susceptible to cold.

For direct sowing, the prime timing for when to plant sunflower seeds lands after the final threat of frost has passed. For transplanting, you can begin the sunflower seeds indoors 4 to 6 weeks earlier than the outdoor planting time in your area.

Starting seeds indoors will give them a bit of a jump-start on their direct sown contemporaries. However, directly sowing sunflower seeds often helps them thrive better.

It truly comes down to how early you want your sunflowers to bloom and how comfortable you are with caring for them and transplanting them.

When to Plant Sunflower Seeds In the Soil

The best time to plant sunflower seeds outdoors will vary based on your local region.

For most, the ideal window is somewhere between March and May, though it can be later in certain regions. This window of time generally encompasses the final threat of frost and allows the soil temperature to reach about 60 degrees.

When to Transplant Sunflowers Outdoors

The timing varies slightly on when to plant sunflower seeds when you are growing them indoors. You can begin them as early as February depending on when the final threat of frost usually ends in your area.

Once you have determined the optimal planting time frame for when to plant sunflower plants outdoors in your particular region, work your way backward by several weeks and begin the indoor planting process.

You will need about 4 to 6 weeks from planting to transplanting to hit the ideal window for when to transplant your sunflower plants outdoors.

Steps to Plant and Care for a Sunflower

Ruby Eclipse Sunflower

Preparing the Soil

Before you make a move on when to plant sunflowers, you need to ensure the soil is ready for them! You can compost your sunflower planting space with a compost mix, or with organic household waste such as egg shells, peels, and coffee grounds.

You also will want to ensure the soil is broken up and churned to allow the taproots to take hold. This may require a bit of vigorous work at the beginning of the planting season, just after the soil begins to soften from that final frost.

In addition, you will need to measure the pH balance in the soil to ensure it is in the optimal 6.0 to 7.5 range. If needed, you can use lime or other organic compounds to raise the levels to the proper range. These can usually be found at a lawn and garden center or nursery.

Direct Sowing Your Sunflowers Outdoors

A sunflower seedling in a garden. Knowing when to plant sunflower seeds is especially important for direct sowing outdoors.

When the time comes, you will want to plant your sunflower seeds 6 inches apart at about 1 inch deep. Then, when the seedlings are about 6 inches tall, thin them out to the strongest blooms, leaving about a foot of space between each.

Another key thing to know about when to plant sunflower seeds outdoors is that this is not a one-time thing! You will actually need to stagger your planting if you would like continuous sunflower blooms throughout the season.

This type of growing is called “succession planting” and is an important part of knowing when to plant sunflower seeds. Every 2 to 3 weeks, you will want to sow a new row of sunflower seeds with the same depth and distance as the first.

This will ensure you have sunflowers to enjoy all the way until the first frost, as it takes about 80 to 120 days for sunflowers to bloom from the time you choose when to plant sunflower seeds.

Beginning Your Sunflower Seeds Indoors

Sunflower Seedlings on a windowsill.

If you’ve decided to get a jumpstart on when to plant sunflower seeds by starting them indoors, you will need peat pots for starters. Place your seeds ½ to 1 inch deep, cover them in soil, then water them and cover them with plastic wrap.

At this point, you can let the seeds germinate for two weeks. Then, remove the covering, water, and continue to moisten until the danger of frost has passed.

At this point, you can harden off the seeds by placing them outdoors for 2 to 4 hours a day for a full week before transplanting them into the soil.

After the hardening off is the ideal time for when to plant sunflower plants outdoors. Carefully cut off the bottom of the peat pot and plant the sunflowers, pot and all, in the soil about 3 feet apart. The peat will break down over time, and your sunflower will begin to thrive!

Caring For Your Sunflowers

A sunflower plant with multiple flower heads.

Whether grown from seed or transplanted from indoors, your young sunflower plants will need to be watered around the root area, roughly 4 inches from the plants themselves. Then, once they become established, you can continue to water deeply but not too frequently.

Watering 2 to 3 times a week will often do the trick. The key is to have the soil constantly moist, but not overly saturated. You may need to water a bit more frequently if the weather becomes too dry or too hot.

Unlike many plants, where watering on the plant bodies themselves is discouraged, you can actually spritz your sunflower heads with water. This will help them maintain a healthy vibrancy throughout their growth cycle.

You can also mix some fertilizer with water to coax out more vibrancy from your sunflower blooms. Start with one that is high in nitrous as the sunflower grows, then switch to a high phosphorus mix when the sunflower blooms.

Just be careful not to fertilize too much, as this can cause the stem to weaken and even break.

Continue to compost the soil throughout the season, and keep an eye on the taller varieties of your sunflower plants. If necessary, you can stake them with bamboo or wood to prevent them from toppling over in the harsher summer winds.

Things You Should Know Before You Plant Sunflowers

Sunflowers in the sunshine.

Sunflowers Are Highly Susceptible to Cold

The biggest reason it is so important to know precisely when to plant sunflower seeds in your area is because of their low tolerance to cold. If you get impatient and are in a rush to direct sow or transplant your sunflower plants, the cold may shock them before they ever get a chance to grow.

Be patient, take time to research your growing zone, and plan accordingly. This will help ensure you pick the perfect timing for when to plant sunflowers in your area and will give the flowers their best chance for a warm start!

If you live in a region that has notably fickle seasons and late frosts, you might consider an alternative for how you grow sunflowers. This leads us to the next thing you should know before you plant sunflowers…

You Can Grow Sunflowers in a Pot

It isn’t terrifically widely known, but sunflowers can be grown indoors in a pot! You need to make sure you have between a 12 to 16-inch pot for dwarf varieties or a 5-gallon pot for large varieties.

In terms of when to plant sunflowers in a pot, the timing is much more relaxed than if you are figuring out when to plant sunflower seeds outdoors. You can typically grow them indoors anytime there is access to sunlight, but be aware they will need high heat and humidity to thrive—even indoors.

Wrapping Up When to Plant Sunflowers

Closeup of a sunflower head.

Now that you know when to plant sunflowers and how to care for them, it’s time to choose the best sunflower variety for your growing needs!

Want to discover more about these beautiful flowers? Then keep reading about sunflowers to learn how to plant and grow them, as well as dry them for décor, and even make sunflower oil!