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Department of Horticulture and Crop Science


Ph.D. Exit Seminar

Nov 19, 2014, 10:00am - 11:00am

Phoebe Gordon, Ph.D. Candidate

Advisor: Dr. Hannah Mathers
Committee: Dr. John Cardina, Dr. Ed McCoy, Dr. Dan Struve


Twenty million acres of land associated with rights-of-way (ROWs) of US highways represent a significant opportunity for the formation of carbon sinks.  However, tree survival in these harsh environments, such as compacted soil and infrequent watering, is needed to achieve this opportunity.  Platanus occidentalis and Gleditsia triacanthos var. inermis were transplanted into air pruning pots or left in control trays for six weeks, then transplanted into 11.4 L containers.  Geohumus was added to the soilless substrate.  Additional P. occidentalis, Robinia pseudoaccacia, and Celtis occidentalis trees were grown to liner size for a Comtil trial in 2012.  The ‘Geohumus’ trees were split between a retractable-roof greenhouse (RRG) or Outside.  At the end of 2011, approximately half of the ‘Geohumus’ trees were harvested, and the remaining trees were overwintered.  In 2012, ‘Geohumus’ trees were outplanted at a highway site.  The ‘Comtil’ liners were planted with or without ComTil.  In 2013, P. occidentalis and Acer xfreemanii ‘Sienna’ were planted in starter pots and transplanted after six (6WIP) or twelve weeks (12WIP) in the starting pots and split between the two environments.  No Geohumus was used this year.  They were harvested at the end of 2013.  Starting pot type had no effect on 2011 harvests when grown for six weeks.  However, in October, 2011, G. triacanthos trees started in Elle had a smaller caliper relative to the other pot types, with the exception of the BRM, after upshifting into 11.4L containers.  In 2013, starting pot type had no effect in the 6WIP group, however at 12WIP differences between the pots were clear, indicating that duration in the pots is important.  At 12WIP, P. occidentalis were largest in BRM due to root pruning being favorable to growth; A. xfreemanii ‘Sienna’ were largest in Jif, control, and BRM pots, which were the largest volume starting pots.  In the 2013 October harvest, 6WIP trees regardless of species were larger than 12WIP trees, I conclude due to root restriction in the form of six extra weeks in the starting pots.  A. xfreemanii 12WIP trees had smaller root masses, increasing the shoot:root ratios over 6WIP trees.  In 2011, Geohumus decreased G. triacanthos shoot:root ratios.  2011 P. occidentalis trees in the RRG had higher shoot:root ratios; which I conclude was due to the RRG being an optimal growing environment compared to the outdoor environment.  Two years since outplanting, G. triacanthos with 0.5 and 2% Geohumus from the RRG, (the largest trees at planting), grew less than all Outside trees with Geohumus, (the smallest at outplanting).  P. occidentalis grew best when started in the RRG, a favorable environment, with a small addition of 0.5% Geohumus.  ComTil had no effect on the three species planted. Further studies should be done to examine the effect of the length of time in starting pot on transplanting establishment, as well the size of tree on establishment in planting in an adverse environment.​

Wednesday, Nov 19th, 2014
10:00 AM to 11:00 AM

139 Howlett (Columbus), video linked to
102 Gourley (Wooster)