[Program information (data, reports, photographs) can be found on the internet at: http://www.uark.edu/campus-resources/cotinus/arboretum_html/planteval.html]

January 2006

This completes the seventh year of the statewide plant evaluation program. The current team of cooperators includes Dr. Jim Robbins, Dr. Jon Lindstrom, and Manjula Carter.

The three test sites are the Hope Research Center (USDA cold hardiness zone 8), the Little Rock/Cooperative Extension Service property (zone 7a), and the Fayetteville Horticulture Research farm (zone 6b). As much as possible the three test sites were prepared in a similar manner. Full sun plants were grown in row-type beds 3’ wide with a 7’ grass alley. Plant groups are planted together (i.e. trees are planted together). Trees are spaced 10’ apart, shrubs 6’ apart, and herbaceous perennials 4’ apart. The Little Rock site was planted on March 14, 2003; Fayetteville was planted on March 10, 2003; Hope planted on March 14, 2003. Irrigation at all three sites is by a drip system. Plants were fertilized and mulched after planting. Post-emergent herbicides were used at all three test sites. No disease or insect control was implemented during the first year. To maintain a tree-like habit, trees are pruned following final growth measurements. Pruning consists of removing the bottom 1/3 of limbs. SHRUBS are NOT pruned. Final growth measurements were taken at Little Rock on October 10; Fayetteville on October 13; and Hope on October 19.

Weather data at all three test sites is attached (see attached graph).

One-gal plants were initiated from UofA seed. Plants grew exceptionally well statewide with no mortality after two growing seasons. All 12 plants are still alive. Plants flowered at all three locations. At Hope, flowering began in mid-August and lasted until the end of September. In Fayetteville, flowering commenced early, July 30^th, and continued until the middle of August. The red calyx remained ornamental into mid October. Average plant size is 86" tall x 80" wide with a mean growth index (GI) of 7.240 m³.

One-gal plants were initiated by UofA from an Arborvillage plant. Three of four plants at Fayetteville died during 2004, the remaining plant flowered in late April. Plants are growing well at Little Rock and Hope. Plants flowered at all three locations in 2004. Flowering starts in early April and lasts for about two weeks. Average plant size is 80" tall x 56" wide with a mean growth index (GI) of 3.598 m³. In general, plants are doing better in zones 7 and 8 than zone 6.

One-gal plants of ‘Hoyt’ were initiated by cuttings at UofA from Univ. of Georgia plants. The cultivar name has changed to ‘Green Splendor’. Plant mortality was very high during the 2004 growing season at Little Rock with all four plants dying. The plants were likely killed in early summer due to heavy rainfall. Pythium/Phytophthora was confirmed on roots of plants. Average plant size on remaining plants statewide is 57" tall x 32" wide with a mean growth index (GI) of 0.890 m³. ‘Hoyt’ is clearly not as aggressive a grower as T. x ‘Green Giant’.

One quart plants were initiated by cuttings at UofA from Univ. of Georgia plants. Nine of the 11 original plants died in 2003 and the remaining plants died in 2004. We suspect that the high mortality is due more as a result of the very small plants we started with than the adaptability of this plant to Arkansas conditions.

One quart plants were initiated by cuttings at UofA from Heronswood Nursery plants. After losing all four plants at Hope in 2003, we now have lost all four plants at Little Rock in 2004. Average plant size at Fayetteville is 42" tall x 52" wide. Plants in Fayetteville began to flower in mid May and continued through August.

Two foot tree tubes were purchased from Forestfarm Nursery. In 2003 we reported that the "Plant is performing well statewide which is amazing considering how small these plants were at the start". The small plant size may have caught up with us. All 4 plants are now dead at Hope and at Little Rock. Two of the four plants died at Fayetteville in 2005. Average plant size on the remaining plants is 29" tall x 17" wide.

Five foot bareroot whips were donated by J. Frank Schmidt Nursery. Plants are struggling in Little Rock and Hope. At these two locations trees suffered shoot dieback. Again, we tend to see significant plant loss when dealing with BR trees. All three trees died at Hope during 2004 and only one tree remains in the trial at Little Rock. All trees are alive in Fayetteville. Mean shoot height on remaining trees is 97" (3" shorter than 2004) with a trunk caliper at 6 inches of 1.5".

Six foot bareroot whips were donated by J. Frank Schmidt Nursery. This clone performed slightly better than ‘John Pair’ with less shoot dieback at the 3 locations. All three trees are now dead at Little Rock. Mean shoot height on remaining trees is 120" (1" increase from 2004) with a trunk caliper at 6 inches of 1.4".