It might sound a little like science fiction, but allelopathic plants can kill or suppress the growth of your garden vegetation. They can also do damage to trees, shrubs, and other greenery. Basically, it’s a survival technique that some plants have evolved – albeit one that can be disastrous to your garden.

Releasing Biochemicals

These allelopathic plants release biochemicals that can inhibit the growth of other species. The biochemicals can be anywhere on the plant – its leaves, flowers, even roots, and bark. As an extension, the allelopathic properties can be in mulch created from the plants.

The list of identified allelopathic plants is long, even though biologists know many more exist. And the processes are various. Some use the simple technique of using their roots to draw all the water from the soil, leaving none for surrounding plants.

Outright poisoners

Others, though, are outright poisoners. For instance, a reed has invaded much of the wetlands in the U.S. Believed to originate in Eurasia, this reed plant exudes a toxic acid from its roots. The acid is so strong that it dissolves the roots of neighboring plants, wiping out the competition.

Black walnut

A good example is the black walnut, which produces the chemical juglone, which affects the germination of seed and many plants’ growth. Garlic mustard is another.

Unfortunately, there is no exhaustive list of allelopathic plants. To date, biologists have identified many, but most of these plants have an economic value of some sort.

Here is a partial list of identified allelopathic plants:

  • Ailanthus (Tree-Of-Heaven)
  • Aster
  • Barley
  • Bearberry
  • Black Walnut(Tomatoes, peppers, eggplants potatoes, Azaleas, pines and irch.)
  • Brassicas (All to varying degrees)
  • Buckwheat
  • Canada Thistle
  • Cedar
  • Corn (specifically corn gluten)
  • Cucumber
  • Dog Fennel
  • Elderberry
  • Eucalyptus
  • English Laurel
  • Ferns
  • Foxtail (Yellow and Giant)
  • Forsythia
  • French-type Marigold
  • Garlic mustard weed
  • Goldenrod
  • Johnsongrass
  • Juniper
  • Kentucky Bluegrass
  • Nutsedge
  • Oats
  • Oregano
  • Rye
  • Rosemary
  • Quackgrass
  • Ragweed
  • Rhododendron
  • Sorghum
  • Sugar Maple
  • Sumac
  • Sunflower
  • Tall Fescue
  • Walnut
  • Wheat

1 comment

  1. Al -

    the tree that grew in brooklyn is the first one. i read all about it after that book. it apparently smells bad and is invasive. i love knowing that theyre allelopathic!! thank you!

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