Sunflower Plant Care – How to Grow Helianthus Annuus

Sunflower Plant Care and Growing Guide

Last Updated on October 31, 2021 by Phil

Everybody knows what sunflowers are. You’ve seen their big, bright yellow-colored blossoms bloom during summertime. And, their seeds used for all sorts of things from food to oil.

But what you may not know is that you can easily grow these cheerful-looking flowers yourself in your home or your backyard.

So, if you’ve ever wondered how to grow and care for them, read on below.

About Sunflowers

Sunflower Plant Care and Growing Guide

Sunflowers are one of the most popular flowers around. They’re great additions to your garden because of the bright color they bring.

Well-known for their vibrant yellow petals and brown cores, these annuals can look very much like daisies.

What not many people know is that there are quite a few varieties of sunflowers around. Besides the giant ones that you’re probably most familiar with, there are also dwarf and perennial varieties around.

This gives you the ability to adorn your garden not only with the big ones that grow up to 16 feet tall and bloom from summer through fall. But, also with smaller ones that reach only 4 feet high.

For the gardener, sunflowers are likewise easy to care for and grow. Their toughness combined with their beauty makes them a good choice if you want to brighten up your garden. Not to mention that they attract bees and butterflies as well.

Of course, last but not least, there are a lot of things you can do with these flowers. They make amazing cut flowers. And, you can harvest their seeds for different purposes, including eating, replanting, or as bird feed.


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Planting Sunflowers

Sunflowers are easy to grow from seeds. As such, it’s cheaper and more efficient to directly sow them into your garden as opposed to buying starter plants from your garden center.

But, either way works.

Once you’ve begun, it does take a little patience since it takes between 80-120 days between seeding and blooming. The difference depends on which kind of sunflower variety you go with.


When to Plant Sunflowers

You can start sowing sunflower seeds directly into the soil once the threat of frost has passed. This is around mid-April to May for locations with colder climates in the north. And, much earlier in the south.

You can likewise use the ground temperature as a guide. Here, you want it to get to at least 55-60 degrees Fahrenheit.

If you happen to live in an area where the growing season is shorter, you can start them indoors to give your plants a head start.


Where to Plant Sunflowers

Your sunflower’s roots like to extend outwards. As such, it’s a good idea to give them enough space when planting. This prevents overcrowding later on.

Plant your sunflower seeds an inch deep and give them 6 inches of space between each other.

Another approach would be sowing many seeds and then thin them out later when they get to 6 inches high. This ensures that you have an abundance of plants to choose from.

And, by leaving the strongest ones, they stand a better chance of producing the best flowers.


How to Plant Sunflowers

Upon planting your seeds, lightly add some fertilizer. Doing so will help them develop stronger roots so that they’re not easily blown over by the wind.

To enjoy continuous blooms all the way until the first frost, you can apply succession planting, wherein you plant new seeds every few weeks so that they bloom at different times all the way till first frost.

It’s also worth mentioning to keep an eye out for birds who may want to scratch the ground in search of seeds. Since they like eating the seeds, you’ll need to keep these birds away with a netting or some other barrier.

Finally, you’ll need to set up some support for some of the taller varieties, at least temporarily.


Sunflower Plant Care

How to Grow & Care for Sunflower

Sunflower Light Requirements

Sunflowers need full sun. As such, you want to plant them in locations where they’re able to receive lots (6-8 hours a day) of bright, direct sunlight.

The good news is, they’re heat tolerant. So, it won’t be a problem leaving them under the intense afternoon sun.


Sunflower Temperature & Humidity

These annuals like it in areas where the summers are long and hot. In fact, that’s when they grow the best.

That said since they’re only going to be around for one season, winter is less of a problem for them.

That’s why you’ll see this garden favorite in zones 2 through 11.


Sunflower Watering

Once sunflowers are established they will tolerate some drought.

However, in the periods before, during, and after flowering, they perform best with deep, regular watering.

While the plant is small, water around the root zone, about 3 to 4 in. from the plant.

Once the plant is established, water deeply though infrequently to encourage deep rooting.

Unless the weather is exceptionally wet or dry, water once a week with several gallons of water.


One of the best features of sunflowers is that they’re not picky about soil. You can grow them in clay, sand, silt or loam.

They’re likewise okay with soil whose pH is between 6.0 to 7.5. So, they don’t mind too much if the soil is slightly acidic or alkaline.

But, given a choice, they do best with loose, well-draining soil.

If you don’t have that kind of soil or don’t want to wait for your soil to improve over time, a good way to overcome poor garden soil is to grow them in beds.

The one thing you want to give them is soil that’s high in organic matter and nutrients. That’s because sunflowers need a lot of “food” to produce their brightly colored flowers.

Sunflower Plant Care Guide


For the most part, sunflowers don’t need fertilizer.

The only time you’ll need to do so is if you have poor garden soil. In this case, using a slow-release fertilizer helps boost their flowers.

That said, you still want to use it infrequently. And, when you do, make sure to use water to dilute your fertilizer since too much nitrogen can prevent them from flowering as well as they normally would.


Harvesting Sunflowers & Their Seeds

How you harvest your sunflower and its seeds will depend on what you plan on doing with them. For the most part, people like cutting sunflowers for bouquets or harvesting the seeds.

So, here’s how to do each.

Cutting Sunflowers for Bouquets and Vases

  • Do this in the morning. You don’t want to do so in the afternoon because the heat will cause it to wilt.
  • Cut the main stem then immediately dip it into water.
  • Make sure to be careful and gentle with them. This reduces the risk of bruising or damage.
  • Ideally, you want to use a tall vase or container so that it supports their stem.
  • Enjoy your bouquet. They should last a week or a little longer than that

Harvesting Sunflower Seeds

The best time to do this is at the end of the season. Here, you have a few choices on what you want to do with the seeds, they include

Eat them as a snack

This requires the most work since you’ll need to rinse and dry them before being able to do anything with the seeds.

Here’s how.

  • Wait until your flowers’ heads dry and start turning down to face the ground.
  • Cut off the flower head along with about 6 inches of stem.
  • Lay the head on a flat surface, then start removing the seeds.
  • Finally, hang them up to dry. If you’re hanging them outdoors, make sure to keep them protected from birds. You can likewise hang them indoors.

Replanting Sunflower Seeds

To replant them, you’ll want to store them in an airtight container and keep them away from moisture. Somewhere like your pantry where it’s dry and cool would be a perfect place to put them until you’re ready to plant them in the ground.

Using Sunflower Seeds as Bird Feed

Using the seeds a bird feed involves the least amount of work. That’s because you can just leave them for the birds to come feed on them.

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