Narrative
'Hull Thornless' (Rubus sp., is a vigorous and productive thornless blackberry cultivar with firm, sweet, fruit. It is named for the late John W. (Jack) Hull, formerly of the University of Maryland. the University of Arkansas, and the U.S. Department of Agriculture, who spent most of his life breeding blackberries and raspberries. 'Hull Thornless' is the fifth in a series of tetraploid, genetically thornless blackberry hybrids developed by the USDA and cooperating agencies (4). It is adapted principally to USDA Plant Hardiness Zones 6-8.Origin'Hull Thornless'. tested as SIUS 68-6-6. originated from a cross made in 1968 by Jack Hull of SIUS 47 x by 'Thornfree' (Fig. 1) and selected by him in 1972 at Carbondale, Illinois. This cross was a repeat of an earlier cross which yielded the promising selections SIUS 64-21-8 ('Dirksen Thornless') and SIUS 64-21-11 ('Black Satin'). Since being selected, 'Hull Thornless' has been tested principally in Maryland and Ohio.Description and performance'Hull Thornless' plants are multistemmed with biennial thornless, vigorous canes. They are essentially crown-forming, and semi-erect after the first year in the field. 'Hull Thornless' is winter-hardy south of a line from Urbana, Ill., to central Ohio, to western Maryland, southern Pennsylvania and northern New Jersey (Zone 6 on the USDA Plant Hardiness Zone Map.) In a greenhouse forcing trial at Beltsville, 'Hull Thornless' needed 750 consecutive hours under 7.2'C to satisfy its chilling requirement. Under conditions of high fertility. and good moisture, plants should be set at 1.8 to 3 m apart and trained onto a 2- or 3-wire trellis. Mature cane bases can be 5 cm in diameter, are self-supporting, and can grow to 4-5 m in a year. Canes are usually topped at 2 meters and lateral shoots are forced for fruiting the following year.'Hull Thornless' is similar to 'Black Satin' in yield and fruit size (Table 1).The thornless blackberries yield very well at an early age (third year) and the yield rankings of the several cultivars at the same age do not vary appreciably with soil difference (compare trial 1 and trial 2 at age 3 years). 'Hull Thornless* and 'Black Satin' are usually the heaviest yielding and the largest fruited of the 5 thornless cultivars, ranging from 8 to 3 g/berry over the harvest season.'Hull Thornless'. on a heavy soil at Beltsville, bloomed 8-9 days later than 'Dirksen Thornless' and 'Black Satin', but it ripened between 'Dirksen Thornless' and 'Black Satin'. On a light soil, 'Hull Thornless' ripened ahead of 'Dirksen Thornless' and 'Black Satin'. Fully ripe fruit of 'Hull Thornless' is firmer, sweeter, colors better and is tougher than 'Black Satin'. 'Hull Thornless' fruit, like that of the other named cultivars, makes a superior jelly or baked product.The superior yielding ability of *Hull Thornless' appears to result from a combination of high number of berries/fruiting lateral and large fruit size, whereas that of 'Black Satin' is attributed to many fruiting laterals/ cane and large fruit size. 'Hull Thornless' and 'Black Satin' do not differ in number or length of bearing canes per plant. The high vigor of 'Hull Thornless' and 'Black Satin' contributes to continued productivity with increasing plant age. 'Dirksen Thornless . , which has lower plant vigor, shows declining yield with advancing plant age. 'Hull Thornless' plants can be well propagated by tip layering, by rooting of I -node softwood stem cuttings (6), or by micropropagation techniques (2).
introduced by USDA tested as SIUS 68-6-6.
Cultivar Synonym= Tested as SIUS 68-6-6
WHY NAMED= Thornless habit
NAMED FOR= Jack Hull, who made the original cross in 1968