Forty-five days after sowing the epicotyl emerges from the growing medium and the tap root averages 15 cm (5.9 inch) in length and represents about 75% of the dry mass of the seedling (Fig. 1C). Seedling emergence is via a hypocotyl hook, but the seed coat containing the exhausted endosperm and haustorial cotyledons may or may not emerge from the medium. In either case, the cotyledons never emerge from the seed coat and are shed along with the remnants of the seed soon after the epicotyl begins to elongate. This type of seed germination where the cotyledons emerge above the soil but remain inside the seed is described as Durian germination (Ng, 1973). de Vogel (1980) has further subdivided Durian germination in to several subcategories of which pawpaw represents the Blumeodendrom type. Pawpaw is the first non-tropical species reported with Durian germination (Baskin and Baskin, 1998).

categories of which pawpaw represents the Blumeodendrom type. Pawpaw is the first non-tropical species reported with Durian germination (Baskin and Baskin, 1998).

STEM CUTTINGS. Propagation from cuttings is difficult in pawpaw and is not currently a viable commercial practice. The ability to propagate pawpaw cultivars from cuttings would present several advantages over using seed or grafting. Plants from cuttings would flower sooner than seedling produced plants and cuttings would eliminate problems with understock suckering in grafted plants. Unfortunately, in a systematic study using over 1200 stem cuttings taken from mature flowering trees only one cutting produced an adventitious root (Finneseth, 1997). In that study, cuttings were taken from flowering trees about 5 years old. Cuttings were taken at 7-d intervals from 17 June to 5 Aug. from trees growing at the KSU research farm. In addition, stem cuttings were collected on 27 July from 26 genetically different mature trees from the Western Maryland Research Experiment Station in Keedysville, Md. Cuttings were treated with indole-3-butyric acid (IBA) as a quick dip solution [0, 25, or 50 mm (0, 5000, or 10,000 ppm)], stuck in flats containing Pro-Mix (Premier Horticulture, Inc., Quakertown, Pa.) and perlite (1:1 vol/vol) and placed under intermittent mist with bottom heat.

trees only one cutting produced an adventitious root (Finneseth, 1997). In that study, cuttings were taken from flowering trees about 5 years old. Cuttings were taken at 7-d intervals from 17 June to 5 Aug. from trees growing at the KSU research farm. In addition, stem cuttings were collected on 27 July from 26 genetically different mature trees from the Western Maryland Research Experiment Station in Keedysville, Md. Cuttings were treated with indole-3-butyric acid (IBA) as a quick dip solution [0, 25, or 50 mm (0, 5000, or 10,000 ppm)], stuck in flats containing Pro-Mix (Premier Horticulture, Inc., Quakertown, Pa.) and perlite (1:1 vol/vol) and placed under intermittent mist with bottom heat.

Experiments using cuttings taken from seedlings of various ages showed a significant impact of juvenility on rooting in pawpaw. Seedlings up to 2 months old showed a high capacity to root. Cuttings treated with 50 mM (10,000 ppm) IBA rooted at 75% and averaged two roots per cutting (Fig. 2A). Seedlings beyond 2 months showed a reduced capacity to form roots. Cuttings taken from 7-month-old seedlings rooted at less than 10% regardless of auxin treatment (Table 1). These data suggest that strategies to revert stock plants to a more juvenile state (i.e., tissue culture or mound layering) will be required before a reliable method for cutting propagation can be obtained.

Root cuttings. Pawpaw is a naturally suckering species, readily forming adventitious shoots from roots in native stands as well as field orchard conditions. Propagation from root cuttings can be an alternative method for multiplication of difficult-to-root species. In addition, shoots derived adventitiously from roots retain a juvenile character and could serve as a source for stem cuttings or explants for tissue culture (Hackett, 1985). Finneseth (1997) studied the impact of root diameter on shoot production in pawpaw. Root pieces were collected from a single pawpaw patch in Greenup County, Ky., during December. The root system was cut into 10 to 12 cm (3.9 to 4.7 inches) long pieces and separated into two groups [less than or greater than 5 mm (0.20 inch)]. Cuttings were dusted with Captan fungicide and planted horizontally, about 5 cm (2.0 inches) deep, in flats filled with perlite and vermiculite (1:1 vol/vol). Flats were placed out of