Henbane Flower

Weed of the Month: Houndstongue & Black Henbane

Some of the first noxious weeds that bloom every spring are Black Henbane and Houndstongue. Both are easy to recognize once they flower.

The houndstongue produces deep magenta-colored, five-petaled flowers along wiry stalks. Each flower will become a cluster of four burs that carry the plant’s seeds and will stick to passers-by like Velcro.

Black Henbane has foul-smelling whitish flowers with purple centers. Once pollinated, its flowers produce pineapple-shaped fruits packed with small black seeds.

Both of these plants are biennial- meaning they live for two years – and if you are seeing them in flower, this is the last year of their life. Before they die, they have one wish – to reproduce! They have until fall to produce as many seeds as they can to assure that their progency will live on for many generations. If they get their wish, we can expect a large crop of these weeds to pop up each spring for many years to come.

But since they are biennial, we have some choice in the matter. Here are our options:

  1. Find flowering adults and dig them out! They have a fairly deep taproot, but if you can dig the plant out below the root crown, it will not come back. Since both of these plants have toxins in their leaves, be sure to use gloves when pulling them out.
  2. Spray flowering adults with herbicide! Visit us at TCWP to find the right herbicide for your situation. Note that once biennial plants have gone to seed it doesn’t make sense to spray them because their seeds will still spread and the plant is at the end of its life cycle anyway. If they are in seed, pull them.
  3. Learn to recognize the plants in their first year – when they are NOT flowering – and spray them with herbicide. This is the most efficient way to control these biennial weeds. See below for identification tips.

Houndstongue looks like a cluster of long, hairy, tongue-shaped leaves with pointy tips. It can be confused with native arrowleaf balsamroot at this stage, as that plant also produces a simple cluster of leaves in its first year and those leaves are a similar shade of green. But look closely at the bases of the leaves and you will notice that balsamroot has a distinctive spade-shaped base while houndstongue leaves simply taper to a point at their base.

Whether the Houndstongue is in its first or second year, it can be pulled out by hand if the soil permits. If chopped out below the root crown, it rarely grows back. If the infestation is too large to hand-pull, purchase herbicide at TCWP and use a surfactant to be sure the herbicide permeates the hairy leaves.

Black Henbane resembles a head of cabbage in its first year. But you wouldn’t want to mistake it for an edible plant! All parts of this plant are very poinonous. If you learn to recognize it in its first year, you can chop it out below the root crown or spray it with a TCWP-approved herbicide.

Whichever option you choose, make sure you get rid of these plants before they go to seed and remember to PlayCleanGo so you don’t spread their seeds into uninfested areas.

Thanks!