Forecasting Life Cycles of Japanese Knotweed and Wild Parsnip


Forecasting life cycles of Japanese knotweed and wild parsnip for better management in Minnesota

Rebecca Montgomery, Forest Resources


Plant phenology is the study of plant life cycle events. Understanding phenology is important for predicting the annual timing of key plant growth stages like flowering or seed development, which are controlled by environmental factors like temperature and sunlight availability.

Farmers use phenology data charts to understand how their crop progress, and when specific management practices can be applied safely and effectively. Similarly, for other invasive plant managers, timing is equally crucial, and MITPPC researchers believe phenology maps for two priority weed species can improve management outcomes.  With the help of Master Gardener citizen scientists, researchers will create publicly available phenology maps for wild parsnip and Japanese knotweed. 

Wild parsnip, a carrot-like perennial that can reach 6 feet tall, poses human health risk due to a phototoxin produced by the leaves. Skin contact with the leaves followed by exposure to sunlight will cause severe blistering. Parsnip can be managed by mowing, but only prior to mature seed development to prevent spread, or herbicide application during specific stages of plant growth. Mowing too late can help to spread seeds.

Japanese knotweed is an aggressive, bamboo-like shoot that can reproduce without seed. Control is extremely difficult, but applying herbicides at certain stages of knotweed development can maximize their effectiveness and stop infestation. 

Research questions

  • How do temperature and photoperiod affect the phenologies of wild parsnip and Japanese knotweed in Minnesota?
  • When are important phenological events for wild parsnip and Japanese knotweed likely to occur in different parts of Minnesota?

Practical implications

Phenology models will help land managers understand the developmental timeline of destructive invasive weeds like Japanese knotweed and wild parsnip in their non-native, Minnesota environment. Ultimately, this information will help match biology to treatment to improve management outcomes. MITPPC partners and stakeholders will be able to use an online tool to get predictions of the expected dates when wild parsnip and Japanese knotweed will reach key stages for effective control.





USA-National Phenology Network, Oregon State University, Minnesota Department of Agriculture, Minnesota Department of Transportation

Research Team:

Rebecca Montgomery, principal investigator, Department of Forest Resources

Stephan Carlson, co-principal investigator, Department of Forest Resources

Abbie Anderson, citizen science coordinator

Byju Govindan, researcher


Header image credit:

"Wild parsnip (poisonous)" by Charlie Day is licensed under CC-BY-ND 2.0