Hemp Dogbane: Extended Seed Dispersal

One of the advantages of walking in the same park regularly — and of taking pictures in different seasons — is that I have the opportunity to see and to review later the ways in which different species develop over the months.

As I approached a patch of Hemp Dogbane in Eliza Howell Park this week, I was struck by how colorful the plants look now in the Speing sunshine. They had shiwn no color in the Winter.

April 14

I also noticed seeds floating away in the breeze, attached to tufts of silk. I find wind seed dispersal fascinating, so I stopped for a closer look.

April 14
April 14

Remembering that I had seen Hemp Dogbane seeds dispersal last Fall, I was curious about the extended released. So I took a look at some photo records.

A picture taken in the Winter doesn’t show any seeds being released at that time, but it does appear that some of seedpods still contain seeds, though most are open and empty.

January 31

According to the Fall photos, the Dogbane was full size (nearly 4 feet) by the middle of September

September 13

And, by that time, the numerous seedpods were well developed.

September 13

Each plant has many seedpods, reportedly 10 to 60 (I have never counted), and each of the seedpods contains dozens of seeds. So a large patch of Hemp Dogbane, such as the one I have been visiting, produces an enormous number of seeds.

The first evidence that I have of seed dispersal from last year’s plants is from September. Most seeds reach maturity by October.

September 14

Hemp Dogbane is also called Common Dogbane and Indian Hemp. The “dogbane” name comes from the fact that the plant is poisonous to dogs (and other mammals). The “hemp” name refers to the fact that native Americans used fibers from the stems as twine.

Hemp Dogbane is native and widespread in the United States. It looks to me similar to some types of milkweed, especially the stems and leaves. Flowering occurs in June – July. Milkweed seeds are also attached to light-weight tufts that lets them float away.

June 21

Even though I return to the same locations time after time, I am always learning. Better said: Because I return to the same locations time after time, I am always learning. Before now, I did not know that Hemp Dogbane seed is “blowing in the wind” in the Fall and again in the Spring.

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