Sawtooth Sunflower – An Amazingly Tall & Beautiful Sunflower

What is Sawtooth Sunflower

Sawtooth Sunflower is a herbaceous perennial flower native to Central North America.  Scientifically known as Helianthus gorsseserratus, it will grow 3-12’ tall in full sun and well draining soil.  Blooming yellow daisy-like flowers for 4-8 weeks in Summer, it attracts a large number of pollinators and birds.[1][2][3][4]

This is one of the tallest plants I grow, easily exceeding 8′ when plenty of water is available. It stands tall as a sentry at the back of our micro-prairie / wildflower meadow providing a beautiful backdrop. One feature of this plant that I really enjoy is how much the flowerheads will sway under windy conditions. Another nice thing is that even though my plants only get sun from primarily the South and East, they seem to stand tall and don’t lean. Although I have heard from others who had them knocked down by high winds.[2]

I’ve got to tell you something interesting about my experience with this flower. First, I never planted it! It naturally showed up in my backyard micro-prairie. And, I was having trouble identifying it. I even when to plant identification groups with pictures asking for advice. But everyone kept suggesting various members of the Helianthus genus…and I didn’t think any of them were correct.

I was almost resigned to just assuming I had some strange sunflower hybrid until I started looking to perennial sunflowers that were native to other parts of the country. That, plus when I noticed the leaves were opposite in the lower portion, and alternate in the upper half of the plant. That is the real secret to identifying this plant!

Native Range of Sawtooth Sunflower

The primary native range of Sawtooth Sunflower the Midwestern United States, from Minnesota to Oklahoma, and Ohio. Other native populations exist in the Dakotas, Texas, Quebec and Ontario Canada.

Sawtooth Sunflower is highly adaptable though, and has established itself outside of it’s native range. It is adventive in New England, the Mid-Atlantic, and the Louisiana/Mississippi/Alabama. It has even spread to Europe, establishing itself in Lithuania. [5]

And although I live in Southern Pennsylvania, it has obviously established itself there either via birds or cultivation. As my first plants just ‘showed up’ in my wildflower meadow, and it took me a very long time to identify them, as I was only looking at Helianthus that was native to my area. Once I realized it could be from a different area, and noticed the changing leaf arrangement (opposite==>alternate), I quickly identified it as Sawtooth Sunflower, Helianthus grosseserratus.

How to Grow Sawtooth Sunflower from Seed

Like other perennial Sunflowers, Saw-tooth Sunflower seeds need to experience a cold-moist stratification period before they are able to germinate. Specifically, Saw-tooth Sunflower needs 30 days cold stratification, or should be Winter Sown.

This mimics what happens in nature, in that the seed naturally falls from the plant in Autumn, and sits in cold-moist soil all Winter. This process will break the seeds dormancy, allowing it to germinate in the Spring.

If it is Spring and you are interested in starting this plant from seed, you can accomplish the stratification requirements using a moist paper towel and the refrigerator. We have a detailed guide on cold-stratifying using the refrigerator here.

Otherwise, the easiest way to start Saw-tooth Sunflower seeds is by Winter Sowing. This is where you plant the seeds in a special DIY container in the Fall/Winter, and you let mother nature do the cold-moist stratification for you. Come Spring, the seeds germinate when temperatures warm up, and get a big growth boost from the greenhouse effect.

We have a detailed guide on Winter Sowing here. And it is by far my preferred method for starting seeds.

How to plant Sawtooth Sunflower seeds

The planting depth of Sawtooth Sunflower seeds in a container is 1/8″-1/4″ (3-6 mm). This may seem shallow, but it is perfectly fine. Most species of seed that are exposed to cold-moist soil will germinate after the required stratification time. The reason for planting them is often just to better protect them from birds/rodents.

The following steps for planting Sawtooth Sunflower seeds assume you are either Winter Sowing the seed, or have already cold-moist stratified the seed in the refrigerator.

1. Fill a suitable container with moist potting soil. Leave a 1/2″-3/4″ gap (6-9mm) from the top of the container. The potting soil should be wet enough that when you squeeze a handful only a few drops of water fall out.
2. Gently tamp the soil firm
3. Place 3-5 seeds on the soil surface. Press them so they have good contact.
4. Cover seeds with 1/8″-1/4″ of moist potting soil.
5. Place the container in a location that receives morning sun and afternoon shade.
6. Keep the soil moist, watering as needed.
7. Once germination occurs, grow the seedlings until they have 2-3 sets of true leaves.

A couple other notes on caring for young seedlings. First, keeping the container in morning sun/afternoon shade is really beneficial. It allows the seedling sunlight for photosynthesis, but protects it from the hot afternoon sun, which can easily dry out small containers.

Second, there is a fungal disease commonly known as ‘damp-off’ disease. It damages the stalk at the interface with the soil, and causes the seedlings to ‘flop’ over and is often fatal. [8] Excessive moisture at this interface of stalk/soil is the primary cause of damp-off disease.

A frequent situation that causes damp-off disease is when you water at night, when this excess moisture just sits there until the next day. If you keep your plants in morning sun, and water in the morning, then the morning sun will evaporate any excess moisture thereby preventing damp-off disease.

I have direct experience with this disease, and ironically enough I lost a number of sunflower seedlings because of it. I was keeping them on our back porch, which received late afternoon sun. By sunset, the containers would be dry, and I would water them. Sure enough, after a week or two the tiny seedlings began flopping over, and I was staking them with toothpicks! Then I learned about why this was occurring, and switched where I grew my seedlings….