JARS 43n1 - Fall Foliage Coloration Of Native Northeastern Azaleas

Fall Foliage Coloration Of Native Northeastern Azaleas
Norman E. Pellett and Karen Alpert
University of Vermont
Burlington, Vermont

Introduction:
An earlier article published in this journal (January, 1988) "Flowering of Flame and Roseshell Azaleas" described the flowering behavior of seed sources of two species of native deciduous azaleas when cultivated in Vermont. The present report describes observations of fall coloration of these and two other native species, Rhododendron canadense and R. viscosum . We collected seed from the northernmost regions and higher elevations where the species are endemic. Knowledge of the behavior of these seed sources may help identify the diversity and ornamental qualities useful for selection and breeding.

Table 1. Location for native azaleas used in this study.
Table 1. Location for native azaleas used in this study. Species Seed Source	undefined Latitude (°N)	undefined Longitude (°W)	undefined Elevation (ft)
Table 1. Location for native azaleas used in this study. R. calendulaceum	undefined	undefined	undefined
Table 1. Location for native azaleas used in this study. Wayah Bald NC	undefined 35°10'	undefined 83°34'	undefined 4200
Table 1. Location for native azaleas used in this study. Mt. Pisgah NC	undefined 35°25'	undefined 82°45'	undefined 5500
Table 1. Location for native azaleas used in this study. BRP 1 408 NC	undefined 35°34'	undefined 82°45'	undefined 4916
Table 1. Location for native azaleas used in this study. BRP 338 NC	undefined 35°50'	undefined 82°03'	undefined 3692
Table 1. Location for native azaleas used in this study. Dolly Sods VW	undefined 38°57'	undefined 79°22'	undefined 4000
Table 1. Location for native azaleas used in this study. Kerens WV	undefined 39°02'	undefined 79°49'	undefined 2250
Table 1. Location for native azaleas used in this study. R. canadense	undefined	undefined	undefined
Table 1. Location for native azaleas used in this study. Packardville MA	undefined 42°21'	undefined 72°23'	undefined 920
Table 1. Location for native azaleas used in this study. Island Pond VT	undefined 44°52'	undefined 72°54'	undefined 1300
Table 1. Location for native azaleas used in this study. R. prinophyllum	undefined	undefined	undefined
Table 1. Location for native azaleas used in this study. Dolly Sods,VW	undefined 38°57'	undefined 79°22'	undefined 4000
Table 1. Location for native azaleas used in this study. Summit NY	undefined 42°33'	undefined 74°32'	undefined 1950
Table 1. Location for native azaleas used in this study. Wendell MA	undefined 42°34'	undefined 72°26'	undefined 1100
Table 1. Location for native azaleas used in this study. Lake Dunmore VT	undefined 43°53'	undefined 73°04'	undefined 600
Table 1. Location for native azaleas used in this study. Wolcott VT	undefined 44°34'	undefined 72°25'	undefined 1196
Table 1. Location for native azaleas used in this study. R. viscosum	undefined	undefined	undefined
Table 1. Location for native azaleas used in this study. BRP 408 NC	undefined 35°24'	undefined 82°45'	undefined 4916
Table 1. Location for native azaleas used in this study. Packardville MA	undefined 42°21'	undefined 72°23'	undefined 920
Table 1. Location for native azaleas used in this study. 1 BRP = milepost number on the Blue Ridge Parkway.

Materials and Methods:
Seeds of four species were collected from numerous plants in woodlands within each natural habitat (seed source) during the years 1978 to 1980 (Table 1). Seeds were germinated in the greenhouse and grown in outdoor beds for two years before planting as 2-yr plants in north-south oriented rows in three replicates. Each plot was planted with 24 plants one foot apart in the rows with rows three feet apart. Plants were irrigated daily with a trickle irrigation system and fertilized twice annually with ammonium sulfate and 15-15-15 applied approximately May 15 and July 1. Soil was a loamy sand.

Fall color was recorded weekly during September and October in 1983 and 1984 in two ways. The quality of fall foliage color was rated where:
1 = no fall color, foliage predominantly green or brown,
2 = poor fall color, foliage other than green,
3 = leaves yellow, purple or red, but not fully developed,
4 = good color, most foliage with predominant shades of yellow, purple, bronze or red, and
5 = highly attractive with uniform yellow, bronze or red leaves.

The mean of these values is presented in Figure 1 and 2 for two species.

A second measure of fall color was recorded as the number of plants in each replicate with predominantly bright red fall foliage. On the last two data collection dates of each year, the percentage of plants retaining leaves was recorded (Table 2).

Means of the two measures of fall coloration were ranked among the seed sources, best to worst on each date for each species (Table 3). The ranks for the source of each species were then summed for all dates each year. This procedure allowed comparison of two methods to determine whether they gave the same results as measures of fall color.

Table 2. Percent of plants retaining leaves during fall foliage drop.
Table 2. Percent of plants retaining leaves during fall foliage drop.	undefined 1983		undefined 1984
Table 2. Percent of plants retaining leaves during fall foliage drop. Species Seed Source	undefined 10/14	undefined 10/21	undefined 10/17	undefined 10/24
Table 2. Percent of plants retaining leaves during fall foliage drop. R. calendulaceum	undefined	undefined	undefined	undefined
Table 2. Percent of plants retaining leaves during fall foliage drop. Wayah Bald NC	undefined 93a 2	undefined 59ab	undefined 88a	undefined 42a
Table 2. Percent of plants retaining leaves during fall foliage drop. Mt. Pisgah NC	undefined 93a	undefined 52ab	undefined 46b	undefined 18a
Table 2. Percent of plants retaining leaves during fall foliage drop. BRP 408 1 NC	undefined 93a	undefined 37b	undefined 53b	undefined 24a
Table 2. Percent of plants retaining leaves during fall foliage drop. BRP 338 NC	undefined 95a	undefined 73a	undefined 76ab	undefined 44a
Table 2. Percent of plants retaining leaves during fall foliage drop. Dolly Sods WV	undefined 92a	undefined 64ab	undefined 54b	undefined 22a
Table 2. Percent of plants retaining leaves during fall foliage drop. Kerens WV	undefined 90a	undefined 48ab	undefined 50b	undefined 24a
Table 2. Percent of plants retaining leaves during fall foliage drop. R. canadense	undefined	undefined	undefined	undefined
Table 2. Percent of plants retaining leaves during fall foliage drop. Packardville MA	undefined 92a	undefined 69a	undefined 83a	undefined 14a
Table 2. Percent of plants retaining leaves during fall foliage drop. Island Pond VT	undefined 94a	undefined 71a	undefined 72a	undefined 3a
Table 2. Percent of plants retaining leaves during fall foliage drop. R. prinophyllum	undefined	undefined	undefined	undefined
Table 2. Percent of plants retaining leaves during fall foliage drop. Dolly Sods WV	undefined 93a	undefined 58a	undefined 67a	undefined 14a
Table 2. Percent of plants retaining leaves during fall foliage drop. Summit NY	undefined 94a	undefined 47a	undefined 33b	undefined 1b
Table 2. Percent of plants retaining leaves during fall foliage drop. Wendell MA	undefined 83a	undefined 42a	undefined 44ab	undefined 16a
Table 2. Percent of plants retaining leaves during fall foliage drop. Lake Dunmore VT	undefined 78a	undefined 47a	undefined 36b	undefined 6b
Table 2. Percent of plants retaining leaves during fall foliage drop. Wolcott VT	undefined 92a	undefined 51a	undefined 58ab	undefined 21a
Table 2. Percent of plants retaining leaves during fall foliage drop. R. viscosum	undefined	undefined	undefined	undefined
Table 2. Percent of plants retaining leaves during fall foliage drop. Packardville MA	undefined 99a	undefined 88a	undefined 94a	undefined 66a
Table 2. Percent of plants retaining leaves during fall foliage drop. BRP 408 NC	undefined 100a	undefined 35b	undefined 23b	undefined 10b
Table 2. Percent of plants retaining leaves during fall foliage drop. 1 BRP = milepost number on the Blue Ridge Parkway. 2 Percent means in a column followed by the same letter for a species are not significantly different using Duncans Multiple Range Test (.05)

Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color.
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color.	undefined Rankings for each species 1
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Species Source 2	undefined 1-5 Ratings		undefined Red Leaves
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color.	undefined 1983	undefined 1984	undefined 1983	undefined 1984
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. R. calendulaceum	undefined	undefined	undefined	undefined
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Dolly S WV	undefined 1	undefined 1	undefined 1	undefined 1
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Pisgah NC	undefined 4	undefined 2	undefined 2	undefined 2
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. BRP 338 NC	undefined 2	undefined 3	undefined 5	undefined 6
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. BRP 408 NC	undefined 3	undefined 4	undefined 3	undefined 4
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Kerens WV	undefined 5	undefined 5	undefined 4	undefined 3
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Wayah NC	undefined 6	undefined 6	undefined 6	undefined 5
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. R. canadense	undefined	undefined	undefined	undefined
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Island P VT	undefined 1	undefined 1	undefined 1	undefined 1
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Packard MA	undefined 2	undefined 2	undefined 2	undefined 2
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. R. prinophyllum	undefined	undefined	undefined	undefined
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Dolly S WV	undefined 1	undefined 1	undefined 2	undefined 1
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Dunmore VT	undefined 2	undefined 2	undefined 1	undefined 5
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Summit NY	undefined 3	undefined 4.5	undefined 3	undefined 5
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Wendell MA	undefined 5	undefined 3	undefined 5	undefined 2
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Wolcott VT	undefined 4	undefined 4.5	undefined 4	undefined 4
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. R. viscosum	undefined	undefined	undefined	undefined
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. Packard. MA	undefined 1	undefined 1	undefined 1	undefined 1
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. BRP 408 NC	undefined 2	undefined 2	undefined 2	undefined 2
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color.
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. 1 Rankings for the two measures of fall foliage color. Plants were rated for quality of foliage and for the percentage of plants having red leaves. For each species on each date, the seed sources were ranked best to worst (1 = best). The ranks were then summed for all dates each year and the sums were ranked for the sources within species.
Table 3. Ranking by seed source of four azalea species of fall foliage color for two measures of fall foliage color. 2 Source of seed is more precisely described in Table 1

Results and Discussion:
Fall color was quite variable from plant-to-plant and among seed sources. Most plants of most seed sources developed good fall color at some time, but the date varied. However, there were differences among seed sources of each species. Good fall color, once developed, was persistent until leaf drop for most plants. Generally, rapid leaf drop (Table 2) occurred between October 14 and 21 during 1983 and between October 17 and 24 during 1984, soon after the peak of color (Figures 1 and 2). Seed sources with slower development of fall color generally dropped their foliage near the same time as others, therefore having a shorter period of good color.

R. calendulaceum , Flame azalea - Plants from Dolly Sods WV had the highest ranking for both measures of fall color during both years (Table 3). Dolly Sods plants had slightly higher ratings for fall color at the peak of color on October 7, 1983 and October 10, 1984 although not significantly higher than other sources (Fig. 1). Plants from the southernmost location, Wayah Bald NC had the poorest color on the three earlier dates (Fig. 1). Other seed sources were less consistent in their relative rankings (Table 3) and mean quality of color (Fig. 1). Interestingly, plants from Kerens, the other West Virginia site, at lower elevation than Dolly Sods, tended to have poor fall color ratings more similar to the Wayah Bald NC site.

Date of leaf drop was quite variable among seed sources for the two years (Table 2). More plants from BRP 338 NC and Wayah Bald NC tended to retain their leaves longer than other sources of the flame azalea although differences were not consistently significant.

R. canadense , Rhodora - Ratings of fall color of plants from Island Pond VT were not significantly different than plants from Packardville MA (data not presented). Color ratings on October 10, 1984 were 4.0 and 3.8 on the 1 to 5 scale for Vermont and Massachusetts plants, respectively. Both sources provided colors among the best for the azaleas compared. However, when the two sources were ranked for the two measures of color, the Vermont plants were better than the Massachusetts plants (Table 3). The date of leaf drop was not significantly different for the two sources.

R. prinophyllum Roseshell azalea - Plants from Dolly Sods WV, the southernmost and highest elevation for the seed sources generally gained their fall color earlier, kept it longer and displayed higher intensity at the peak than other sources (Fig. 2). Dolly Sods plants generally had the highest color rankings (Table 3). Other sources were not significantly different from each other over the two years. The five sources were not significantly different in percent of plants retaining leaves (Table 2).

R. viscosum , Swamp azalea - Plants from Packardville MA, a low elevation northern site were compared with plants from BRP 408 NC, a southern site with higher elevation. Both sources had good fall color, but Massachusetts plants had higher ratings on most dates during the two years (data not shown). When ranked for the two measures of color over two years, the Massachusetts plants were ranked higher every time (Table 3). The Massachusetts plants retained their leaves longer than North Carolina plants during both years (Table 2).

Conclusions:
There were differences in the timing and quality of fall color based on location of seed source. For R. calendulaceum , the northernmost source, Dolly Sods WV, tended to have the best fall foliage color and the southernmost source, Wayah Bald NC had the poorest fall color and also retained its leaves longer than other sources. For R. canadense , the northernmost source, Island Pond VT may have had a slightly better fall color, but time of leaf fall was not different.

For R. prinophyllum , the southernmost but highest elevation source, Dolly Sods WV had the earliest and best fall foliage color of the seed sources, but there was no significant difference from other sources in leaf fall. For R. viscosum , the northernmost source, Packardville MA had better and more consistent fall color than the plants from BRP 408 NC and retained their foliage better.