Native plant fights invasive mugwort to reclaim Bush Terminal Park

One day, in the heat of summer, you might catch a strong whiff of honey and jasmine as you walk through the neighborhood. If you see neither honey nor jasmine but instead find yourself in front of a fenced-in lot, staring at a mass of plants with narrow, dark green leaves, wine-tinted stems growing higher than your knees and tipped with clusters of white flowers that are far too dainty for the surrounding urban decay, you may have found hemp dogbane, or Apocynum cannabinum. Make sure you give it a salute—even though it could kill you.

Dogbane doesn’t fully describe this plant’s destructive power. It is a bane to anything that has a heartbeat. It is in the same family as milkweed, but unlike milkweed, hemp dogbane is too toxic to nurture future generations of monarch butterflies.

The leaves and stems of both plants ooze a poisonous white sap full of cardiac glycosides, which cause cardiac arrest. The monarch butterfly is just one of the insects that have evolved to use milkweed’s toxicity to their advantage; in imbibing the sap they also become poisonous to predators. Hemp dogbane is too toxic even for insects that have evolved to imbibe poison all day.

The monarch butterfly is the most famous insect to rely on milkweed, but the most ubiquitous is the invasive oleander aphid. They look like tiny orange beads and might be lovely except that they infest milkweed and then crap all over their leaves, turning them sticky, black and gothic. If there are enough of them crowding the milkweed you’ll notice that they wag their abdomen in unison, creating a pulsating wave of orange bodies. For them it is not enough to simply feast on the milkweed and besmirch its leaves, they must also dance upon their host’s body.

You will not see aphids twerking on hemp dogbane. Insects seem to know which member of the Apocynaceae family not to mess around with. The flowers are a different story. They are white and modest, but their fragrance is not. It fills the summer breeze like a marquee, inviting fluttering and buzzing masses to feast upon its nectar and pollen—which are not poisonous.

It’s an important lesson. Hemp dogbane does not exist to be murderous, it just sets boundaries. It does not nurture the hordes that are sustained by common milkweed, but does deign to host the larvae of a couple species that would not be able to exist without it, including the dogbane beetle. It can even be magnanimous to humans. The same leaves and stems that could kill us if we eat them have been harvested by Native Americans for centuries and turned into a fiber to make rope and fabric for clothing.

Making a good quantity of rope is only possible with a great quantity of plants. Luckily, hemp dogbane is as vigorous as it is toxic, spreading through clones that emerge from rhizomatous roots that spread underground. Due to its aggressive nature hemp dogbane is not often cultivated. It plants itself. It grows in untended areas of Sunset Park and if cut it will grow back vigorously, meeting a setback with a comeback—and this is another lesson it can teach us. It takes over empty lots, growing through cracks and rubble, duking it out with mugwort, another denizen of neglected spaces. Mugwort is an invasive species that is truly a bane, taking over anywhere the sun shines, including great swaths of land at Bush Terminal Park, but even there hemp dogbane is hot on its heels. Sometimes it even vanquishes it, elbowing it out of the mosh pit of plants that grow in inaccessible areas of the park. I wish it could make mugwort drop dead as it has done to so many of its enemies, but reclaiming land is never easy. If there’s any plant that’s vigorous and ferocious enough to do so, it’s hemp dogbane.