Herbicide spritz technique for control of herbaceous invasive plants

The herbicide spritz technique is suitable for precise control of broad-leaved herbaceous invasive plants, especially clonal species such as Canada goldenrod and perennial sunflowers. This technique makes use of a high concentration of an oil-soluble herbicide (such as Garlon 4) diluted to 20% with a penetrating bark oil. Only a few drops of herbicide on the meristem or one or two leaves is all that is necessary. The herbicide quickly penetrates the leaf and spreads throughout the plant. Response is very rapid.

During the mid-summer growing season, the sprayed plant usually shows a discoloration or wilting response in a few hours. Within several days even leaves on that stem that have not been sprayed begin to respond, and within a week the whole plant is moribund. If all stems of the clone are spritzed, then the complete clone is eradicated and does not return the following year.

Although labor intensive, this technique is very selective and hence suitable for control of invasive perennial weeds in planted or remnant prairies and savannas.

The herbicide mix used is identical to that used for basal bark treatment of woody plants. Hence, both woody and herbaceous weeds can be dealt with on the same pass through a natural area. 

Dense clone of invasive sunflower

Single stem that has been spritzed (red dye used as marker).

During the early summer growing season, response is very rapid. These plants had been spritzed the day before. Note discoloration and death of leaves.

Clone that had been spritzed two weeks before.

 Canada goldenrod stems that had been spritzed a few days before. Only one or two leaves were spritzed on each stem. A "wipe" technique can also be used with a sponge or glove applicator. Care must be taken to ensure that each stem of the clone is treated.