Identification and Reproduction

Identification: 

• Yellow bush lupine is also known as tree lupine. This flowering plant is in the legume Fabaceae family. 
• It is an evergreen shrub growing up to 2 m tall. 
• Leaves are green to greyish green and are palmate. There are 5 to 12 leaflets on each leaf. Leaves are also covered in fine silky hairs. 
• Flowers are found in a terminal stalked raceme, light yelllow, pea-like and very fragrant. Blooms occur in the spring. In certain locations flowers can be blue, liliac of purple. 

• Seedpods are 4-6cm long, hairy and contain 8-12 seeds each. 

Reproduction: 

• Yellow bush lupine only reproduces by seed. 
• It is a prolific seed producer and seeds are very persistent. 
• Seedpods will explode and disperse seeds short distances. 

Habitat & Ecology

• It prefers well-draining soil but an grow in nutrient-poor sites. 
• It is shade intolerant but drought tolerant. 
• Yellow bush lupine can withstand temperatures that reach −12 °C. 
• Typically found on rock bluffs, dunes, and steep slopes. 

Impacts

Ecological: 

• It is a good nitrogen fixer and will alter the soil chemistry of the environment. This can inhibit the growth of native plants that are adapted to low nitrogen levels. 
• It is capable of hybridizing with native lupines and can threaten the native ecosystem. 

Management

Prevention is a high priority for this plant. 

• Do not plant or distribute this plant. 
• If you have a flower arrangement with this plant please dry and dispose of it in the garbage. 

Mechanical/Manual Control: 

• Manual eradication is the most effective method. This includes hand-pulling and weed wrenching. These techniques remove the roots entirely and lead to eventual death. 
• Plants should be removed prior to seed set in June. 
• Remove yellow bush lupine as early as possible, before they are able to cause permenant damage to the soil chemistry. 
• Depending on the stage of infestation, native plants may need to be replanted to help restore the environment. 

Resources

For more information check out the University of Minnesota: Department of Horticultural Science's Restoration and Reclamation Review here.  

For more details on historic and managment controls please check out the Cal-IPC's plant report on Lupinus arboreus.  

Header photo (Krzysxtof Ziarnek).