Keeping An Eye On Hemp Dogbane: Wildflower Wednesday

– Posted in: Native/Invasive

The email from my neighbor to the south was ominous. “There’s a plant I’ve never seen before on the north side of your property along the road. It’s already grown into a big patch and I’m afraid it might be swallowwort.” I had read that swallowwort was highly invasive, but I had never seen any around here. Still, any plant that appeared suddenly and in large quantities needed to be investigated. We’re already trying to keep wild parsnip and garlic mustard from taking over, and we’re fighting Tartarian honeysuckle as well. We sure didn’t need another invasive species in the neighborhood.

I walked over to the area my neighbor had described, and realized I had mistaken the plants he was talking about for milkweed. But now that I looked carefully, I realized this was something else. I took a few pictures and went inside to research. Between my reference books and the internet, I finally figured out it was hemp dogbane (Apocynum cannabinum).

Hemp dogbane flower

If you are familiar with milkweed, you can probably see the family resemblance in hemp dogbane.

I had never heard of or seen this plant before, and yet according to the USDA, it is native to all fifty states. It’s not surprising that my neighbor mistook it for swallowwort and I mistook it for milkweed, because all three are from the same family (Apocynaceae) and have similar leaves and flowers. All three have rootstocks that creep underground, making large colonies, and have those distinctive seedpods that open up, releasing lightweight flying seeds into the air.

Are your warning bells going off yet? The Ladybird Johnson Wildflower Center warns, “This species can become a serious weed as it is aggressive and difficult to control.” Illinois Wildflowers notes “In moist open areas, clonal colonies can spread aggressively from underground rhizomes.” Penn State Extension gets more explicit: “Ten-day-old seedlings already have perennial capabilities; they can resprout if cut off at ground level. Roots grow laterally and send up new shoots, so one hemp dogbane plant can quickly turn into a large patch. In fields under cultivation, tillage chops the roots into small pieces. A root segment less than one inch long with a single bud can produce a new plant.” By now I am hyperventilating. This plant will take over the world, if you let it.

But it’s a native plant!

hemp dogbane patch

This is the patch of hemp dogbane growing on the north side of our property. Looks pretty well established, doesn’t it?

What good is dogbane?

Aren’t native plants good? Don’t we want them in our gardens? Not if you’re a corn farmer: “Control in corn is difficult because hemp dogbane seedlings emerge one to three weeks earlier than corn seedlings, and shoots continue to emerge throughout summer.” I noticed Nan Ondra had a picture of hemp dogbane in her recent blog post. I asked her how hemp dogbane behaved in her field. Her answer? “It’s more aggressive than goldenrod.” Uh-oh. I had to remove goldenrod from one of my garden beds; it just took over. I’d better be on the alert.

dogbane or euphorbia

I thought this was the ‘Bonfire’ euphorbia I had given up for lost, but now I’m wondering if it is a dogbane seedling. I feel like I can’t be too paranoid.

But Nan also pointed me to What Good is Dogbane?, which pictured over a dozen different pollinators that feed on hemp dogbane. Yes, it’s a native plant, and there are plenty of bees, butterflies, moths, beetles, bugs, and flies that feed on it.

Decisions, decisions

It’s only a matter of time before it shows up in the lawn. Will weekly mowing keep it in check? Sooner or later, it will show up in my flower beds–if it hasn’t already. Will I recognize it in time? Right now it’s on the very edge of our property, along a creek–the equivalent of a fence row. Should I try to curb its growth, without trying to eradicate it, or let it do whatever it wants? What do you think?

Posted for Wildflower Wednesday, created by Gail of Clay and Limestone, to share wildflowers/native plants no matter where you garden in the blogosphere. “It doesn’t matter if we sometimes show the same plants. How they grow and thrive in your garden is what matters most. It’s always the fourth Wednesday of the month!”

About the Author

Kathy Purdy is a colchicum evangelist, converting unsuspecting gardeners into colchicophiles. She would be delighted to speak to your group about colchicums or other gardening topics. Kathy’s been writing since 4th grade, gardening since high school, and blogging since 2002.

Autumn is a second spring when every leaf is a flower.

~Albert Camus in Albert Camus quotations

Comments on this entry are closed.

Rosie Hamilton September 9, 2015, 8:22 am

I think it’s best to let it grow and see what happens.

Iris Taylor September 8, 2015, 4:05 am

I’ve never seen this flower before, it’s beautiful! Hope you can manage to keep it.

Kendall September 4, 2015, 7:56 am

Hey Kathy, I am a new gardener. I don’t understand Apocynum cannabinum and Dogbane are the same thing, right? Thanks for sharing this precious information with us.


Kathy Purdy September 4, 2015, 11:04 am

Yes, Apocynum cannabinum is the scientific name for Dogbane.

Barbara August 31, 2015, 9:41 am

Kathy, o.k. Now I’m curious. It looks like a lot of different things. Am on the hunt to see if I can find it on my usual trails – and if I do, take some good pictures & a mental note that it’s not something I want carousing in my garden

Fred August 31, 2015, 9:05 am

Can it be contained in a plastic pot in the garden?

Kathy Purdy August 31, 2015, 11:55 am

Well, Fred, I don’t know. Since it’s already in the wild areas of our property, I don’t think I want to move it into the garden.

Kathy Sturr of the Violet Fern August 31, 2015, 8:24 am

Oh, and thank goodness it’s not Swallowwort – evil! We have a park nearby, Robert Wehle, that is infested with Swallowwort where SLELO is studying and conducting management.

Kathy Sturr of the Violet Fern August 31, 2015, 8:18 am

There are natives that are also listed as invasive as they can disrupt an environment such as Black Locust Tree and Cup Plant. I would begin control immediately – every year. Only because I have seen how plants can take over ha ha. I am paranoid, but still I would try to knock it back each year to keep it in check. It’s a pretty plant at least!

gail eichelberger August 30, 2015, 6:55 pm

I am glad they are calling it aggressive and not invasive but, I wouldn’t want another seriously tough colonizer to deal with unless I love it. Is there a reason to take it out if mowing with contain it? Is there something that you could plant that could duke it out with the dogbane? Maybe a goldenrod! Let us know what you decide to do!