Habitat Restoration – Weed of the Month February 2022

Himalayan Blackberry

I would say the invasive that best defines a love/nonlove relationship here on the refuge is Himalayan blackberry. The love comes in the form of a tasty summer treat, and a plant that helps shield some of the bigger ash tree trunks from beaver. The nonlove is the pain associated with working on or around not just patches, but individual stems that will grab your foot and pull you to the ground when you least expect. With the ability to spread and aggressively outcompete native species, Himalayan blackberry is one of our most visible and widespread invasive plant species.

A couple other negatives about Himalayan blackberry is its role as a fuel ladder during wildfires, and the load they put on branches in the trees they climb. A sail made of blackberry canes can eventually drag down the biggest of branches in a strong wind.

The good news is Himalayan blackberries can be mowed out although it can take multiple years and multiple mowing. If you can mow or clip it back two or three times a year you will be forcing the plant to constantly draw on the energy reserves in the root system to repair and regrow stems and leaves. Eventually you will exhaust its reserves. A good example is the field at the Refuge’s port entrance. We mow Carty field one to two times a season with tractors and the only blackberries left are within the planting rows.

Here on the Refuge our process is to mow out the patches and spray the regrowth. We usually wait until the regrown stems are a couple feet long and have eight or more leaflets to ensure enough surface area to take up the herbicide. We use triclopyr and a surfactant to treat the regrowth. You don’t have to mow before spraying, but it will cut down on the amount of herbicide needed and you don’t have to worry about people browsing the berries after you have just sprayed. If you can spray only once, fall before the first frost is the best time.

-Keith Rutz, FRNWR Habitat Restoration Coordinator