MEMBER PROFILE 



UNH Research-Cathy Neal 



BY MELISSA MOORE 



At the winter annual meeting 

 Cathy Neal, UNH Extension 

 L Professor and Ornamentals Spe- 

 cialist, discussed her work investigat- 

 ing the merits of the pot-in-pot pro- 

 duction system for NH growers. This 

 production system, which first gained 

 a foothold in the South in the early 

 1990's, has spread throughout the 

 U.S. Here in the Granite State, Neal 

 set out to answer if a tree's growth 

 rate could be enhanced with the pot- 

 in-pot system. A second research 

 question focused on whether or not 

 trees could be overwintered in this 

 climate with the PIP system. 



Pot-in-pot (PIP) has been pro- 

 moted as a production method that 

 moderates root zone temperatures and 

 eliminates root mortality. During the 

 summer months, is has been observed 

 that roots in the western quadrant of 

 the root ball have been killed by ex- 

 treme high temperatures. The most 

 critical days are not limited to the 

 summer when ambient temperatures 

 soar above 90 degrees Fahrenheit. 

 Even a beautiful fall day in October 

 with a bright, clear blue sky can di- 

 rect intense solar radiation on the pot 

 and cause high temperatures that will 

 kill roots. Neal added that root mor- 

 tality will jeopardize tree top health 

 since it leads to a loss of chlorophyll 

 and protein and inhibits photosynthe- 

 sis. 



Neal indicated that a healthy root 

 system is the cornerstone for produc- 

 ing a quality tree. She reminded 

 growers that roots are the most fragile 

 and vulnerable part of a tree to tem- 

 perature damage therefore it's wise to 

 pay close attention to root health. 



The optimal zone for root develop- 

 ment and maintenance is 60 -80 de- 

 grees Fahrenheit. At 86 degrees F., 

 root growth will be retarded. The le- 

 thal range is 100 degrees F. and 



above. Conversely, root growth is re- 

 tarded at temperatures less than 60 

 degrees F. Winter hardiness is very 

 dependent on species, but some roots 

 die in the mid-to lower 20 degrees F., 

 pachysandra will survive down to 15 

 degrees F., and yews and rhoddies 

 will stand temperatures down to 10 

 degrees F. 



Neal began her research in June 

 2001, and continued to collect data 

 through 2002. The on going project 

 will yield additional research conclu- 

 sions after the 2003 growing season. 

 The tree species used in Neal's project 

 included 'Donald Wyman' Ccabapples 

 and a lilac cultivar. Five different pro- 

 duction systems were included in the 

 project. A total of ten plants of each 

 species were grown under each of the 

 five different methods. The five differ- 

 ent production methods were: field 

 grown, standard container, The Above 

 Ground System TM (an above 

 ground container with an inverted pot 

 over it, providing an air space be- 

 tween the pots), bag-in-pot and pot- 

 in-pot. 



Throughout the project, thousands 

 of temperature readings were collected 

 every 15 minutes and analyzed. The 

 temperature readings proved beyond 

 a doubt, that roots in containers 

 were frequently exposed to high 

 temperatures in the lethal range. 

 Consequently strategies for root zone 

 moderation are essential for producing 

 quality trees. The readings for the 

 winter months showed that the media 

 in the pot-in-pot system closely 

 followed soil temperatures. Conse- 

 quently, Neal concluded that anything 

 a NH grower would decide to 

 overwinter in the field, could safely 

 be overwintered with the pot-in-pot 

 system. 



In the first growing season, all con- 

 tainerized stock outgrew the field 

 grown crabapples. However in year 2, 



when looking at tree growth no 

 significant difference could be deter- 

 mined between containerized stock 

 and field grown. Neal said, "While 

 some researchers have concluded that 

 the PIP system has contributed to a 

 growth enhancement, the current 

 project underway at the UNH Horti- 

 cultural Farm didn't follow this 

 trend." Neal added, "At the end of 

 year 2, the top growth and caliper 

 size of the trees under all systems was 

 amazingly consistent." 



When the crabapple trees were har- 

 vested and removed from the liner 

 pots in November 2002, another 

 benefit of the PIP system surfaced. 

 Neal and her research assistants 

 weighed the dry weight of each root 

 ball. The data showed the pot-in-pot 

 trees had more root mass than trees 

 grown under other systems. Field 

 grown trees had the least harvested 

 root mass. The impact of the heavier 

 root ball, and how that impacts tree 

 survival and growth after transplant- 

 ing to the landscape, will be investi- 

 gated in ftiture growing seasons. 



Neal pointed out in addition to 

 the root zone moderation benefits, 

 pot-in-pot has won over many grow- 

 ers because it allows in-place over 

 wintering and could be viewed as a 

 labor saving production method. The 

 system lends itself to trickle irrigation, 

 a watering method requiring much 

 less water to maintain a crop com- 

 pared to overhead watering. With 

 trickle irrigation run-off is minimized 

 and the water is supplied right where 

 it is most needed for plant growth. 

 Pot-in-Pot is favored over field grown 

 trees because the entire tree in the 

 liner pot can be lifted right out of 

 the socket pot with an in-tact root 

 system. The PIP system offers good 

 year round access to a nursery crop. 



18 



The Plantsman 



