First Advisor

Olyssa Starry

Date of Award


Document Type


Degree Name

Bachelor of Science (B.S.) in Environmental Studies and University Honors


Environmental Science and Management




Orobanchaceae, Sedum -- Growth, Green roofs (Gardening), Plant growing media -- Contamination, Host-parasite relationships




An increasing presence of the parasitic plant Orobanche uniflora has been observed on green roofs in urban areas such as Portland, Oregon. Although little is known about these plants, they are believed to be detrimental to host plants such as sedums that grow on green roofs. Orobanche uniflora takes over the host plant’s cellular structure and uses this to take in nutrients. This poses a problem for green roof succulents because if the host plants are killed by the parasite then the green roofs will not be able to function as effectively. Green roofs may also be contributing to an increase in the presence of the parasite that could threaten less common succulents in less urbanized areas. The purpose of this study was to determine if there is a difference in growth and health of sedum plants grown in clean soil and plants grown in soil infected by the parasite. Sedum Album and Kamtschaticum were chosen as the test plants since they are common green roof plants. The plants were grown in either clean or infected soil with 4 replicates of each group. The plants were grown in a greenhouse for 6 weeks and then evaluated for change in greenness. The analysis was done by using photoshop to isolate and total the number of green pixels in for photographs of each plant. The resulting analysis shows that all plants increased in greenness regardless of soil type. Sedum Album plants had the lowest overall change in greenness and the largest difference between clean soil growth and infected soil growth. The p-value for Sedum Album was 0.05, meaning parasite infection was likely the cause of decreased growth rates in the plants. The Kamtschaticum had very similar growth rates between the test groups and a p-value of 0.31, which means the growth rates were likely not affected by the parasite. Because the length of the study was so short, further research needs to be done in order to evaluate the relationship between the parasite and the host plants. It would also be beneficial to measure other parameters of plant health, such as height and root length, as these may be better indicators of the effect the parasite had on the sedum plants.


In Copyright. URI: This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier