December, 2001

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

The three test sites are the Hope Research Center (USDA cold hardiness zone 8a), the Little Rock/Cammack 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. Plants groups are planted together (i.e. trees are planted together). Trees are spaced 10’ apart, shrubs 6’ apart, and herbaceous perennials 4’ apart. For shade requiring plants, separate evaluation sites were established under natural shade at all three test sites. Little Rock site was planted on March 10, 1999; Fayetteville was planted on March 11, 1999; Hope planted on April 13, 1999. 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 has been implemented since the initial planting. Every year, the oak and Styrax are pruned following final growth measurements to maintain a tree-like habit. Pruning consists of removing the bottom 1/3 of limbs. Final growth measurements were taken at Little Rock on November 2; Fayetteville on November 13; and Hope on November 9.

In general, the best growth for the 15 shrubs and 2 trees continues to be the Little Rock site. Plants at the Little Rock site do receive a few hours of shade generally during the morning hours. Fayetteville and Hope are very exposed, full sun sites. The Fayetteville site is characterized by consistent winds.

All of Arkansas was devastated by a severe ice storm just after Christmas 2000. Some of the plant losses in the trial were simply due to the extreme ice loads and not necessarily cold injury. In Fayetteville, however, December 2000 was 10 degrees below normal and this cold had a significant effect on the survival of plants best adapted to Zone 7 and warmer. Some areas of Arkansas experienced an extremely hot and dry summer at some sites in 2001 (see attached graph). The dry weather extended well into fall 2001. Fayetteville however had a "normal" summer with sufficient rainfall throughout the season and temperatures near normal means.

Flowerwood Nursery donated 3-gal plants. This was a great test winter for the Encore azaleas. There is no way to conclude much about Encores at Hope (z 8) this year as all plants were crushed under piles of ice and mostly destroyed.

Data from Fayetteville clearly indicates that Autumn Amethyst™ is the hardiest of the three Encores in our trial. Plants in Fayetteville flowered poorly in the spring of 2001 due to the winter injury to the flower buds. Performance continues to be exceptional at Little Rock. Flowering appears first on Autumn Amethyst™. In Little Rock flowering began in late March. Significant re-bloom was noted in July and continued until each site had a hard freeze or later (plants still in flower as of December 3 in LR). Flowering started in Fayetteville in mid April. Re-bloom in Fayetteville occurred in September of 2001 and continued through the beginning of November. Flowering was abundant ant he plants attracted much attention through the two month bloom period. The plant appears to be slightly wider (45") than tall (27"). This is the tallest of the three Encore azaleas being evaluated.

Flowerwood Nursery donated 3-gal plants. This was a great test winter for the Encore azaleas. There is no way to conclude much about Encores at Hope (z 8) this year as all plants were crushed under piles of ice and mostly destroyed. Flowering notes indicate that Autumn Coral™ started flowering 1 week after Amethyst in the spring but flowered for a longer period of time (into late May). Autumn Coral™ was rated as the best for a spring flower display in LR. Significant re-bloom was noted in mid-July and continued through until each site had a very hard freeze. Plant habit is clearly wider (27") than tall (13"). Habit of Autumn Coral™ is very similar to Autumn Embers™. The plants in Fayetteville did not flower in spring 2001, but did slowly recover from the harsh winter. They did not flower in fall 2001, but they are still alive.

Flowerwood Nursery donated 3-gal plants. This was a great test winter for the Encore azaleas. There is no way to conclude much about Encores at Hope (z 8) this year as all plants were crushed under piles of ice and mostly destroyed. Spring flowering period is very similar to Autumn Coral™ but not quite as lengthy. Summer/fall re-bloom appears to begin a similar to Autumn Coral™. Overall shape is similar to Autumn Coral™ (33" wide x 17" tall). The single plant in Fayetteville did not flower in 2001 and was severely set back by the winter cold.

Flowerwood Nursery donated 3-gal plants. Like the Encore Azaleas, the camellias were all but wiped out at Hope by the ice storm. The 2000 winter was a good test winter for camellia as 3 of 4 plants in FV were killed and the remaining plant is barely hanging on. The planting site in FV is adjacent to a campus building so it receives maximum protection in zone 6b. No flowers were observed. Plant shape is slightly wider (23") than tall (17").

Flowerwood Nursery donated 5-gal plants. Performance was good at all Little Rock and Hope. Based on results from Fayetteville (FV) we would conclude that this is the least cold hardy of the three hollies tested. Zone 6b may be approaching the northern limit for this plant. The plant is slightly taller (78") than it is wide (67"). This plant has good landscape qualities with the burgundy color to the emerging foliage, clean foliage, and 5-6 mm red fruits.

Flowerwood Nursery donated 5-gal plants. Performance was good at all three test sites. The plant is clearly taller (94") than it is wide (45"). A strong pyramidal shape is developing without shearing. This holly lends itself well to a narrow screen or hedge plant.

Flowerwood Nursery donated 7-gal plants. Performance was good at all three test sites. Plants have an upright pyramidal shape (63" tall by 49" wide) without pruning. Fruit in Fayetteville began to ripen in mid-October.

Greenleaf Nursery donated 3-gal plants. Performance was good at Little Rock and Fayetteville. Abelia continues to struggle at Hope. Flowering began in mid June and continued sporadically into fall. Significant reversion from the variegated form back to a green-leafed form was noted. Most of the flowering in Fayetteville was on these reverted shoots. This plant is rather ugly in Fayetteville; a combination of dead twigs, vigorous reversion shoots and depauperate variegated shoots. The variegation does not appear to be very stable. Average plant width (40") is twice the height (24"). Based on performance and reversion problems the program will likely not recommend this cultivar.

Hines Nurseries donated 5-gal plants. Performance was good at all three sites. This plant has finally come of age and is taking on a strong rounded shape. The shape is approaching a ball in the second year (63" wide x 62" tall). Peak flowering was noted in May in Little Rock and very early June in Fayetteville

Greenleaf Nursery donated 1-gal plants. Performance was outstanding at all three sites. Flowering generally began at the end of April and continued for one month. Flowering in Fayetteville is later, beginning in mid-May and peaking at the beginning of June. Several plants in Fayetteville exhibited winter injury on the inflorescence; they were shortened by the extreme cold in December 2000. A real asset to this plant is the rich maroon fall color that is intense by Thanksgiving. Plants continue to spread quickly by rhizomes. Average plant size is 35" tall by 61" wide.

Rhaphiolepis Bay Breeze â

Hines Nurseries donated 1-gal plants. Performance was good at LR and Hope. Based on this past test winter, it would appear that zone 7 is the safe northern limit for this cultivar. Three of the 4 plants were killed to the ground in Fayetteville. Re-growth on the surviving plant was limited.

Flowering begins in early April and then again late summer. The plant develops a very attractive deep maroon winter foliage color that makes a nice backdrop for the light pink flowers in early spring. Plant habit is clearly spreading (31'') rather than tall (14''). Foliar leaf spot was noted on the plants.

Loropetalum Plum Delight â

Hines Nurseries donated 1-gal plants. Performance was mixed again this year. Plants grew vigorously in Little Rock but struggled at Fayetteville and Hope. For some unknown reason ¾ plants at Hope died this growing season and ¼ died at Fayetteville as a result of the hard winter. Flowering began in late February and continued until a hard late spring freeze. Plants tend to throw late season flowers based on temperatures and precipitation. When in flower this plant is hard to beat. Plants at Little Rock are enormous (109" wide x 84" tall) considering the age and size of the original plant.

Plants in Fayetteville did not flower this spring, the second year that this has happened. There was significant flowering in the interior of the plants in November; however, flowers were hidden by the foliage.

Morningside Nursery donated liners. Considering the size of the initial liners this is remarkable growth and performance for small plants planted out in field conditions. Flowers started to appear in early July but peaked toward the end of August. Plants continue to flower into September. Of the two genetic dwarfs being tested, this is clearly the best for Arkansas. Average size is 33" wide by 23" tall. Plants in Fayetteville started to flower in late July or early August and ceased about three weeks later.

Morningside Nursery donated liners. Like ‘Pocomoke’, considering the size of the initial liners, it is amazing what growth and survival occurred. Three plants of this cultivar still survive in Fayetteville. This cultivar is routinely killed to the ground in Fayetteville and it is slow to re-grow the following season. Like the plants in Little Rock, the buds barely open. Flowering started in early August.

‘Chickasaw’ almost teased us when it came to flowering. Beautiful, glossy, red ceramic flower buds appeared in July but were slow to open until late August or into early September. Buds almost appeared ‘blind’ as the petals barely emerge from the calyx. The overall impact of the flower display was not as good as that seen with ‘Pocomoke’. Average size is 16" wide by 13" tall.

Morningside Nursery donated liners. This crapemyrtle began flowering in mid-June and continued for months (mid-September)! Growth is correlated with location. Best growth occurred in Hope and least growth in Fayetteville. Flowering in Fayetteville commenced in late June in Fayetteville and on least one plant continued into August. Despite claims to more winter hardiness, this cultivar was killed to the ground in Fayetteville in the winter of 2000-2001. Powdery mildew was noted at the Little Rock location. Average size is 38" wide by 38" tall.

Greenleaf Nursery donated 5-gal plants. The thin, gray bark of Styrax is very susceptible to damage on the SW quadrant. This resulted in the death of several plants.

Dramatic flowering is from mid-April to early May. The average plant height is 114" with a trunk diameter at 6" of just over 2".

Pittman Nursery donated 1-gal plants. A preliminary assessment is that this plant is Quercus x comptoniae. Growth was good at all three sites. Since this plant is of seed origin, the plant habit is beginning to fall into two categories. One group is developing a nice open tree canopy, while those in the second group show a strong tendency to produce many recurving lower branches that will make this plant difficult to work with and require more initial pruning maintenance. The average plant height is 132" with a trunk diameter at 6" of just under 2.8". Those trees with an open, tree canopy are worthy of additional propagation and more extensive testing.

The Ornamentals team would like to express their sincere appreciation to the cooperating nurseries (Flowerwood Nurseries, Hines Nurseries, Greenleaf Nursery, Morningside Nursery, and Pittman Nursery) for donating the plants for this season’s trial and to the Arkansas Nurserymen’s Association for financial support.

Eucommia ulmoides (J. Frank Schmidt Nursery)

Acer buergerianum (J. Frank Schmidt Nursery)

Rhus aromatica ‘Gro-low’ (Bailey Nursery)

Viburnum x ‘Conoy’

Viburnum awabuki ‘Chindo’ (Univ. of North Carolina)

Diervilla lonicera ‘Copper’

Ternstroemia gymnathera Bronze Beauty™ (Flowerwood Nursery)

Rhaphiolepis indica Eleanor Taber™™ (Flowerwood Nursery)

Rhaphiolepis indica Olivia™™™™™™™ ( Flowerwood Nursery)

Lonicera nitida ‘Ernest Wilson’

Viburnum x ‘Emerald Triumph’ (Bailey Nursery)

Itea ilicifolia (Heronswood/ microprop.)

Itea oldhamii (Heronswood/ microprop.)

Agarista populifolia Leprechaun^™ (Flowerwood Nursery)

Crataegus sp. (Blossomberry N./Nat’ Arb)

Quercus x Crimson Spire™ (J. Frank Schmidt N.)

Gelsemium sempervirens Lemon Drop™ (Flowerwood)

Deutzia setchuenensis var. corymbiflora (Heronswood/ cuttings)

Viburnum utile (Wilkerson Mill/ cuttings)

Fontanesia fortunei 'Titan' (Forestfarm/ cuttings)

Cotinus obovatus (J. Frank Schmidt N.)

Acer negundo 'Sensation' (J. Frank Schmidt N.)

Pyrus fauriei Korean Sun^™™ (J. Frank Schmidt N.)

Thuja x 'Green Giant' (The Botany Shop (Joplin, MO)

Agapanthus 'Headbourne Hybrids' (Colvos Creek N (WA))

Rhododendron Peppermint Twist - R. hyperythrum (Briggs Nursery)

Ilex x koehneana ‘Martha Berry’

Magnolia grandiflora 'Hasse' (Briggs Nursery)

Magnolia 'Vulcan' (Briggs Nursery)

Prunus lusitanica (Forestfarm N.)

Ceanothus x delilianus ‘Gloire de Versailles’ (Hines N)

Acer saccharum Fall Fiesta™™ (Bailey)

Cephalotaxus harringtonia v. prostrata

Clethra alnifolia 'Sixteen Candles'

Cliftonia monophylla Chipola Pink™™; (Flowerwood)

Loropetalum chinense Petite Delight™™; (Hines Nursery)