Table 1. End of season tree height, spread, shoot length, vigor and trunk cross-sectional area (TCSA) for seven grafted paw-paw varieties and one nongrafted seedling strain planted in 1998 near Belleville, Ill.
Taylor 44.0 c 56.3 95.6 c 47.4 36.8 c 21.0 8.0 64.7 2.23 bc
Davis 47.5 bcy 54.6 77.0 c 40.9 39.3 c 21.9 6.6 37.3 1.54 c
Variety Ht (cm) Spread (cm) Avg shoot length (cm) Vigor parameters, 2000
1998z 1999 2000 2000 1998 1999 Shoots >30 cm (11.8 inches) long
Rebeccas Gold 47.3 bc 55.8 108.5ab 50.0 39.7 c 23.5 8.4 52.6 2.45 bc
Sunflower 68.0 a 71.9 117.9ab 54.0 61.3 a 29.6 11.3 49.6 2.78 c
Overleese 52.3 abc 58.8 98.9c 50.3 46.3 bc 33.7 8.6 47.5 2.27 bc
Prolific 66.4 a 72.9 129.9 53.0 59.4 ab 29.4 12.3 53.4 3.44 b
Wells 62.3 ab 66.7 114.8 46.0 55.8 ab 28.3 9.5 56.9 1.99 c
Seedling 50.5 abc 76.5 134.0 a 57.8 50.5 abc 39.3 9.5 63.6 4.54
Px 0.010 0.160 0.001 0.233 0.005 0.218 0.104 0.218 0.049
(no./tree) (%/total) TCSA (cm2)
vative Least significant difference was used for mean separation. An arcsine transformation of percentage data was conducted prior to analysis of variance and back-transformed for presentation purposes (Little and Hills, 1978).
Tree survival rate was 96.5%, 100%, and 100% for 1998, 1999, and 2000 respectively, and did not vary by variety. Seedling survival rate was 100%. Following the end of the first growing season, 1998, the pawpaw varieties Sunflower and Prolific were significantly taller than ‘Taylor’ but not the other varieties (Table 1). Tree height was not different between varieties in 1999. However by the end of 2000 ‘Prolific’ and the seedling trees were significantly taller than ‘Davis’, ‘Taylor’, and ‘Overleese’. Canopy spread measured at the end of the third season was not influenced by variety.
Average shoot length in 1998 followed a similar pattern as tree height due to minimal branching of the whip by seasons end (Table 1). Average shoot length in 1999 was considerably less than in 1998, primarily due to increased shoots per plant from whip bud breaks (WBB, Table 2) and less vigorous growth. Average shoot length was not influenced by variety in 1999. In 2000 both number and percentage of shoots >30 cm (11.8 inches) long were not influenced by variety. In 2000, the seedlings had larger trunks than ‘Davis’, ‘Taylor’, ‘Rebeccas Gold’, ‘Overleese’ and ‘Wells’ (TCSA, Table 1). Number of multiple (tertiary) branched scaffolds formed by the end of the third year (2000) did not differ significantly among varieties and generally reflected initial WBB number measured at the end of 1999 (Table 2).
lowed a similar pattern as tree height due to minimal branching of the whip by seasons end (Table 1). Average shoot length in 1999 was considerably less than in 1998, primarily due to increased shoots per plant from whip bud breaks (WBB, Table 2) and less vigorous growth. Average shoot length was not influenced by variety in 1999. In 2000 both number and percentage of shoots >30 cm (11.8 inches) long were not influenced by variety. In 2000, the seedlings had larger trunks than ‘Davis’, ‘Taylor’, ‘Rebeccas Gold’, ‘Overleese’ and ‘Wells’ (TCSA, Table 1). Number of multiple (tertiary) branched scaffolds formed by the end of the third year (2000) did not differ significantly among varieties and generally reflected initial WBB number measured at the end of 1999 (Table 2).
Following the winter after planting (1998–99), tip dieback occurred on all trees. Subsequent growth as represented by WBB number and end-of-season (1999) shoot lengths were compared. There was no significant difference among varieties in WBB number or the average length of the shoot that broke at the top of the damaged whip (DASL) or in the length of the longest shoot on the whip (LSL) (Table 2). However, for each variety, average LSL was always greater than DASL, with these mid-stem and lower shoots often becoming the dominant scaffolds on the tree, out-growing the apically located shoots. DASL ranged from 15.8 to 44.6 cm (6.22 to 17.56 inches) while shoots originating lower on the whip grew longer [LSL 30.4 to 50.6 cm (11.97 to 19.92 inches)]. This habit of dominant, lower axillary shoot growth should be considered as early training and pruning regimes are developed for pawpaw. Based on observations from natural tip loss made in this study, as branch heading cuts are made,
represented by WBB number and end-of-season (1999) shoot lengths were compared. There was no significant difference among varieties in WBB number or the average length of the shoot that broke at the top of the damaged whip (DASL) or in the length of the longest shoot on the whip (LSL) (Table 2). However, for each variety, average LSL was always greater than DASL, with these mid-stem and lower shoots often becoming the dominant scaffolds on the tree, out-growing the apically located shoots. DASL ranged from 15.8 to 44.6 cm (6.22 to 17.56 inches) while shoots originating lower on the whip grew longer [LSL 30.4 to 50.6 cm (11.97 to 19.92 inches)]. This habit of dominant, lower axillary shoot growth should be considered as early training and pruning regimes are developed for pawpaw. Based on observations from natural tip loss made in this study, as branch heading cuts are made,
Table 2. Whip bud break (WBB), longest shoot length (LSL), distal axillary shoot length (DASL) and branch number characteristics for seven grafted pawpaw varieties and one nongrafted seedling strain planted in 1998 near Belleville, Ill.
Variety WBB\n(no./tree)z 1999 Shoot length (cm) 2000 Branch/shoot no.
Davis 4.8 31.1y 21.4 3.9 16.0
Taylor 4.8 30.4 21.7 3.6 13.4
Rebeccas Gold 4.0 36.7 15.8 3.8 16.4
Sunflower 4.3 40.1 26.2 4.1 22.9
Overleese 3.9 44.2 35.5 3.6 17.9
Prolific 4.4 42.1 23.3 3.8 23.6
Wells 4.3 38.8 26.1 4.0 18.0
Seedling 3.8 50.6 44.6 3.8 15.3
Px 0.810 0.232 0.206 0.962 0.061
LSL DASL (scaffolds/tree) (shoot tips/tree)