University of Arkansas Plant Evaluation Program

2002 Plants/ Arkansas Plant Evaluation Program2004 Final Report

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

2004 Final Report

February 2005

 

 

Plants initiated in Spring 2002:

 

This completes the sixth 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 April 18, 2002; Fayetteville was planted on April 5, 2002; Hope planted on April 5, 2002.  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 November 19; Fayetteville on November 16; and Hope on November 28.

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

 

Acer saccharum Fall FiestaTM

Bailey Nursery donated 8’ BR plants.  Performance has been fair at Little Rock and Hope and good in Fayetteville..  The performance so far emphasizes the challenge we face in planting larger BR trees and should not reflect negatively on the tree itself.  Statewide average tree height is 104” with a trunk caliper @ 6” of 1.6”.

 

Magnolia grandiflora ‘Hasse’

Briggs Nursery donated 1-gal plants. Performance has been good so far.  There have been no plant losses statewide. Based on the color variation in underside leaf surface pubescence, we wonder if we have more than one clone.  Plants really took off in growth in this second year increasing in height statewide by 32”.  Statewide average tree height is 85” with a trunk caliper @ 6” of 2.4”.

 

Magnolia בVulcan’

Briggs Nursery donated 1-gal plants.  Performance has been good at Hope, fair at Little Rock, but abysmal in Fayetteville.  At Fayetteville in 2003, two plants died and the third killed to the ground with limited regrowth the following spring.  Plants did not flower in 2004.  Foliage is distorted by an unidentified leaf spot in Little Rock.  Statewide average tree height is 81” with a trunk caliper @ 6” of 1.3”.

 

 

Clethra alnifolia ‘Sixteen Candles’

Griffith Propagation Nursery donated 2” liner plants. Both clones of Clethra tested performed very poorly at all three sites. By the end of 2004 all 9 plants are dead at all three test sties.  If it had simply been this cultivar, we would have concluded high mortality was related to small plant size. However, the sister clone ‘White Dove’, also performed poorly during an Arkansas summer.

 

Clethra alnifolia White DoveTM

Flowerwood Nursery donated 3-gal container plants. Similar to sister seedling, ‘Sixteen Candles’, ‘White Dove’ struggled during an Arkansas summer.  Flowering is about 1 week later than ‘Sixteen Candles’.  Statewide 5 of the 12 plants are dead. Average plant size is 18” tall by 16” wide. 

 

Chamaecyparis thyoides ‘Emily’

Cuttings were rooted from University of Georgia plants and planted as a 1-gal.  Growth rate was outstanding at all three test sites.  This might be a good substitute for those looking for Juniperus virginiana.  Average plant size is 92” tall by 80” wide.

 

Cliftonia monophylla Chipola PinkTM

Flowerwood Nursery donated 3-gal container plants.  Six of the nine plants planted, including all the plants in Fayetteville, died during the first summer.  Average plant size on remaining plants is 46” tall x 53” wide.  Plants display a lovely soft pink flower from April 7 to May 7 in Little Rock.

 

Daphniphyllum macropodum

1-gal plants were purchased from Colvos Creek Nursery.  We are very impressed with the performance of this broadleaf evergreen in Little Rock and Hope during the first two years even though it was planted in full sun at all three sites.  Most of the growth continues to be vertical.  This plant would benefit from pruning at an early age which we do not do in our program.  Plants in Fayetteville were seriously affected by cold weather in October and November of 2002 and all three died.  The bark on all three plants has split at the base of the plant.  All three plants growing in Little Rock died in 2004.  The deaths at LR would appear to be related to root rot in our heavy soil and a very wet spring. Average plant size at Hope is 24” tall x 14” wide.

 

Distylium myricoides

1-gal plants were purchased from Nurseries Caroliniana.  Performance was good at all three sites.  Plants flowered in the first year. Average final plant size was 31” tall by 68” wide (broader than tall).  Plants flowered the last 2 weeks in March in Fayetteville, Little Rock and Hope.  Up close the flower is exquisite.  This might make a nice spreading broadleaf evergreen in place of junipers or hollies.

 

Ilex × koehneana ‘Martha Berry’

Flowerwood Nursery donated 3-gal container plants.  Plant growth was good at all 3 sites.  Average final plant size was 76” tall by 50” wide.  Foliage is a dark blue-green.  New growth on this holly was slow to harden-off in Fayetteville and was damaged by the first frost of the season.

 

Michelia skinneriana

1-gal plants were purchased from Nurseries Caroliniana. Performance was good at Hope and Little Rock.  All plants are dead at Fayetteville (zone 6).   Average plant size was 61” tall by 59” wide.  Foliage is a very clean, medium green.  Plants flowered in Little Rock in late March but the unique 1” flower is hidden in the foliage.

 

Prunus lusitanica

 1-gal plants were purchased from Forestfarm Nursery.  Growth was good at Little Rock and Hope. All plants are dead in Fayetteville.  Average final plant size was 37” tall by 36” wide.

           

Rhododendron ‘Peppermint Twist’

Briggs Nursery donated 4” liner plants. Truly a remarkable success story in Little Rock and Hope for the first two years.  Only one plant remains statewide and that is located at Little Rock. Plants, while not thriving, did well considering they were grown in full Arkansas sun.  Plants in Little Rock flowered in late April and lasted for about 2 weeks. 

 

Thuja plicata ‘Spring Grove’

1-gal plants were purchased from Nurseries Caroliniana. Here is an interesting situation since we now understand that Thuja × ‘Green Giant’ (2001 plant) and this culitvar are likely identical.  Plants grew exceptionally well at all three sites.  One plant died at Little Rock in 2004 due to what looks like a root rot. Average final plant size was 96” tall by 44” wide.

 

Trochodendron aralioides

1-quart plants were purchased from Colvos Creek Nursery. Plants started fine but were killed by the hot Arkansas summer.  A shadier location is suggested for future plantings.

 

Ceanothus x delilianus ‘Henri Desfossé’

Hines Nurseries donated 5-gal container plants.  The plants came labeled as ‘Gloire de Versailles’ but they are actually the cultivar ‘Henri Desfossé.  ‘Gloire de Versailles’ has larger, broader leaves and bigger flower panicles.   This plant is probably the star for the year.  These plants begin to flower in May and as of late October were still in flower.  Unbelievable flower display and the fruits mature with a beautiful cherry red that lasts until a hard frost.  Average final plant size was 68” tall by 100” wide.

 

The Ornamentals team would like to express their sincere appreciation to the cooperating nurseries (Flowerwood Nurseries, Briggs Nursery, Dr. Michael Dirr- University of Georgia, Griffith Propagation Nursery, and Hines Nurseries) for donating the plants for this season’s trial and to the Arkansas Green Industry Association for financial support.