Autumn’s Showiest Flower

October 7, 2009 | By | Comments (5)

Is it a weed or a wildflower? A blessing or a curse? Everyone has an opinion (although only the Grump’s is correct), but if you’re looking for the showiest blooms of autumn — those which routinely cause multi-car pileups in front of your house due to gawking motorists — here they are.

 

Fall 2009 009

The name? Helianthus angustifolius aka swamp sunflower or narrowleaf sunflower. Native to the eastern United States, this perennial puts on an autumn show like no other. One reason is that it produces masses of bright yellow blossoms up to 3 inches wide. Another is that in good soil, it can easily grow 8 to 12 feet tall.

Swamp sunflower is blooming right now in the South. The Grump is not alone in his judgment of its impact. Nancy Goodwin, creator of fabled Montrose Gardens in Hillsborough, North Carolina, places it prominently in her border. “When it blooms,” she notes, “it’s like turning on the lights.” Here’s a photo from her tropical border taken in late September just as the sunflowers are opening up.

Fall 2009

So why do some people hate swamp sunflower? Because it won’t stay put. It spreads aggressively by underground rhizomes and will quickly take over a garden if you let it. Plant one plant and next year you’ll have 10. The year after that, you’ll have 100.

The image below, taken in the Grump’s garden, proves the point. I was given a single division some years ago and left it to its own devices. This is what it looks like today on the side of my house.

Fall 2009 024

Beautiful? Yes. Problem? Could be, unless you belong to the Swamp Sunflower Society of America and dream of the day all ugly humans are supplanted by billions of swamp sunflowers.

Fortunately, there are easy ways to control the spread of this plant. For instance:

1. Swamp sunflower plants are easy to pull up and throw away. Just firmly grasp the stem next to the ground and yank. Nothing to it.

2. The wetter the soil is, the faster swamp sunflower spreads. Planting in regular or drier soil slows it down.

Another problem people have is that this plant grows so tall that strong winds and rain can break the stems. But the wise Grump knows how to prevent this. Wait until your swamp sunflowers grow to 4 feet tall and then cut them down to 2 feet. This will probably limit their ultimate height to 6-7 feet, but if that’s too tall, cut them back again. Cut them back no later than July, though, so they have time to form lots of flower buds.

Where can you get swamp sunflower? Well, anyone who has it will gladly share some, I promise you. Niche Gardens is a good mail-order source. They offer ‘Mellow Yellow’ (NOT what you’re thinking), featuring soft yellow blooms; and ‘Gold Lace,’ which grows shorter and spreads less rampantly than the species. Sunlight Gardens is another good source.

What Swamp Sunflower Likes

Light: Full sun

Soil: Moist; lots of organic matter; takes poor drainage

Pests: Powdery mildew

Growth Rate: Fast

Bloom Time: September, October

Where It Grows: Throughout the South, Zones 6 to 10

COMMENTS

  1. Cameron (Defining Your Home Garden)

    I have been growing helianthus angustifolius ‘First Light’ for three years. I’ve not found this one to be spreading aggressively. It stays in nice clumps and I have to divide it in order to get it to move!
    I now have it in 5 places (some are barely a stem) because of division. The clumps are shining so brightly right now. I must add that the orange Benary’s Giant Zinnias look great beside it (a happy accident in the outer garden, since I’ve never planted orange zinnias).
    The deer munched it vigorously last summer, but have left it alone this year. It is one of those “deer resistant” plants that are sometimes NOT, depending upon the hungry deer.
    Cameron

    October 7, 2009 at 7:49 pm
  2. Tom (7th Street Cottage)

    I had someone give me several clumps of this plant in spring. They’re blooming now while most of my other plants have already started falling asleep for the winter. I love it. I think I’ll plant it all along the right of way the city mows in June. That’ll teach them, right? RIGHT?

    October 9, 2009 at 8:04 am
  3. Grumpy Gardener aka His Excellency

    Go for it, man!

    October 9, 2009 at 3:57 pm
  4. Pam

    I saw something like this yesterday at Savannah’s botanical gardens. They told me it was “mexican daisy” but when I searched the internet, I found it was more like the “mexican marigold”.It was at least 6-7 feet tall with masses of bright yellow flowers. I’m wondering if it was really this one that the grump in talking about?

    October 10, 2009 at 8:30 am
  5. Grumpy Gardener aka His Excellency

    There is a “Mexican mint marigold,” but it doesn’t get anywhere near 6 feet tall and the flowers are small. Without a photo, I can’t tell what plant you saw.

    October 10, 2009 at 10:37 am