HORTSCIENCE 37(4):697–700. 2002. 1973; Shreve, 1972; Shreve and Miles, 1972), J. regia (Gautam and Chauhan, 1990), J. sinensis (Kwon et al., 1990), and hybrids (Reil Early Season Softwood Cuttings et al., 1998; Serr, 1964). The objective of this study was to deter- Effective for Vegetative Propagation of mine the conditions necessary for successful hardwood or softwood cutting propagation of Juglans cinerea butternut. Preliminary studies in 1998 with hardwood cuttings collected in May resulted Paula M. Pijut1 and Melanie J. Moore in 12.5% rooting when cuttings were treated with 29 mM K-IBA, but only three out of six USDA Forest Service, North Central Research Station, 1992 Folwell Avenue, plants survived acclimatization to the field St. Paul, MN 55108 (Pijut and Barker, 1999). Softwood cuttings collected in June and July resulted in 63% to Additional index words. butternut, adventitious rooting, threatened species 70% rooting when cuttings were treated with Abstract. Juglans cinerea L. (butternut) is a hardwood species valued for its wood and 62 mM K-IBA or 74 mM IBA, but again only edible nuts. Information on the vegetative propagation of this species is currently unavail- three out of 68 plants survived overwintering able. Our objective was to determine the conditions necessary for successful stem-cutting and acclimatization to the field. Based on propagation of butternut. In 1999 and 2000, 10 trees (each year) were randomly selected these observations, for the years 1999 and from a 5- and 6-year-old butternut plantation located in Rosemount, Minn. Hardwood 2000, we examined the effects of propagation stem cuttings were collected in March, April, and May. Softwood cuttings were collected time, type of cutting (hardwood vs. softwood), in June and July. K-IBA at 0, 29, or 62 mM in water and IBA at 0, 34, or 74 mM in 70% and K-IBA or IBA treatment on rooting per- ethanol were tested for root induction on cuttings. The basal end of cuttings were dipped centage, number and length of roots regener- in a treatment solution for 10 to 15 seconds, potted in a peat : perlite mixture, and placed ated, and overwintering survival. Success in in a mist bed for 5 to 8 weeks. Rooted cuttings were gradually hardened off from the mist propagating unselected, but canker-free, trees bed, allowed to initiate new growth, overwintered in a controlled cold-storage environ- could be applied to propagating older, elite, ment, and then outplanted to the field. For hardwood cuttings, rooting was greatest for disease-resistant clones, especially as selected those taken in mid-May (branches flushed out), 22% with 62 mM K-IBA and 28% with 74 grafted trees become established in planta- mM IBA. Softwood cuttings rooted best when taken in June (current season’s first flush of tions. new growth or softwood growth 40 cm or greater) and treated with 62 mM K-IBA (77%) or 74 mM IBA (88%). For 1999, 31 out of 51 rooted softwood cuttings (60.8%) survived Materials and Methods overwintering in cold storage and acclimatization to the field. For 2000, 173 out of 186 rooted softwood cuttings (93%) survived overwintering and acclimatization to the field. Hardwood cuttings. In 1999 and 2000, 10 Chemical names used: indole-3-butyric acid-potassium salt (K-IBA); indole-3-butyric trees (10 different trees each year) were se- acid (IBA). lected from a 5- and 6-year-old butternut field plot located in Rosemount, Minn. Hardwood cuttings were collected at specific growth Juglans cinerea L. (butternut) is a hard- is seldom found in pure stands (Rink, 1990). stages: dormant (30 Mar. 1999 and 29 Mar. wood species native to the northeastern United Butternut canker disease, caused by the fun- 2000); budbreak (27 Apr. 1999 and 2 May States and adjacent Canada, ranging from New gus Sirococcus clavigignenti-juglandacearum 2000); and branches flushed out (13 May 1999 Brunswick to Georgia and west to Minnesota N.B. Nair, Kostichka and Kuntz (Nair et al., and 19 May 2000). Six to 12 cuttings (25 cm in and Arkansas (Rink, 1990). It is valued for its 1979), was first observed in 1967 and is caus- length) were taken from each tree at each wood and edible nuts (Ostry and Pijut, 2000). ing widespread mortality, and is threatening collection date. Two years of growth were Quality butternut wood commands a high native butternut tree survival (Cummings pruned from the remaining branches (after last market price for many uses, including furni- Carlson, 1993; Nair, 1999; Orchard et al., 1982; hardwood collection date) to encourage sprout- ture, cabinets, veneer, paneling, specialty prod- Ostry, 1997, 1998; Tisserat and Kuntz, 1984). ing. Cuttings were placed in polyethylene bags, ucts, and carving. In addition, the wood can be The fungus, believed to be introduced (Furnier held on ice, and transported to the St. Paul stained to resemble black walnut. The edible et al., 1999), causes perennial cankers on all greenhouse, where the cuttings were processed nuts are oily and sweet, consumed by humans, aboveground parts of the tree. All age and size the same day. Stems were recut to between 20 and are an important food source for wildlife. classes of trees are susceptible. The cankers and 23 cm in length. The basal 3 cm of cuttings Juglans cinerea is considered to be one of the cause the wood to turn dark brown to black in were treated by dipping for 10 to 15 s in either most winter hardy (USDA Hardiness Zone an elliptical pattern, which reduces the quality 0, 29, or 62 mM K-IBA dissolved in deionized range of 3 to 7) of the Juglans species (Dirr, of the wood and renders many stands unmar- water or 0, 34, or 74 mM IBA dissolved in 70% 1990). Butternut is not a common species, and ketable. Eventually, the girdling effect of ethanol. Cuttings were inserted vertically to a multiple coalescing cankers kills the tree. depth of 5 to 7 cm in Deepots™ (D40) (Stuewe Received for publication 18 May 2001. Accepted Butternut is propagated easily from seed and Sons, Corvallis, Ore.) containing a moist for publication 17 Nov. 2001. We gratefully ac- (Brinkman, 1974), but the canker fungus is medium of 1 perlite : 1 peat (v/v). Cuttings in knowledge R. Daniel Lineberger and Margaret Pooler for their constructive review and suggestions for also seed-borne (Orchard, 1984; Orchard et Deepots™ were placed under intermittent mist improvement of this manuscript, and David J. Rugg al., 1981). Vegetative propagation will be re- (15 s every 18 min) on a greenhouse bench for statistical analyses. Mention of a trademark, quired to produce clones of genotypes selected with bottom heat maintained at 27 °C. Twelve proprietary product, or vendor does not constitute a for resistance to butternut canker disease. Graft- hours of supplementary irradiance (from 0600 guarantee or warranty of the product by the U.S. ing to black walnut rootstock (Ostry and Pijut, to 1800 HR) were provided by high-pressure Dept. of Agriculture and does not imply its approval 2000) and in vitro culture (Pijut, 1997) of sodium lamps (60 µmol·m–2·s–1 at bench top), to the exclusion of other products or vendors that butternut are successful, but both are time- and greenhouse temperature was maintained also may be suitable. ± ° 1 consuming processes with variable success. at 22 2 C. After 6 to 8 weeks, cuttings were To whom reprint requests may be addressed. Cur- There are few reports of vegetative propaga- harvested and number of cuttings rooted, num- rent address: USDA Forest Service, North Central Research Station, Hardwood Tree Improvement and tion of butternut through cuttings (Pijut and ber of roots per cutting, and individual root Regeneration Center, Purdue Univ., Dept. of For- Barker, 1999). Rooting is reported for other lengths were recorded. Data were analyzed estry and Natural Resources, 1159 Forestry Build- Juglans species: J. hindsii (Lee et al., 1977), J. using statistical programs for categorical data ing, West Lafayette, IN 47907. E-mail address: microcarpa (Shreve, 1990), J. nigra (Carpen- (Rugg, unpublished), log linear modeling [email protected] ter, 1975; Farmer, 1971; Farmer and Hall, (SPSS, 1998), and logistic regression (Mehta HORTSCIENCE, VOL. 37(4), JULY 2002 697 6903, p. 697-700 697 6/25/02, 1:08 PM PROPAGATION & TISSUE CULTURE and Patel, 1996). The number of roots per Table 1. Effects of time of collection and rooting treatment concentration on rooting percentage, root count, cutting were square root transformed and the and root length of Juglans cinerea hardwood cuttingsz. data analyzed using linear regression. The Rooting Date of collectiony data for root lengths were log transformed and treatment 1999 2000 the data analyzed using linear regression. Rooted cuttings were transplanted in (mM) 30 Mar. 27 Apr. 13 May 29 Mar. 2 May 19 May Treepots (Tall One) (Stuewe and Sons) con- Rooting (%) taining a moist medium of Sunshine SB-40 0 K-IBA 0 ax 0 a 0 a 0 a 0 a 11.1 a bark mix (Sun Gro Horticulture, Bellevue, 29 K-IBA 0 a 7.7 ab 10.5 ab 9.1 a 6.3 ab 16.7 ab Wash.), with 14N–14P–14K Nutricote 62 K-IBA 0 a 0 b 10.5 b 0 a 12.5 b 22.2 b 0 IBA 0 a 0 a 0 a 0 a 0 a 11.1 a timed-release fertilizer, and returned to inter- 34 IBA 0 a 0 ab 0 ab 0 a 6.3 ab 11.1 ab mittent mist for 1 week. Rooted cuttings were 74 IBA 0 a 0 a 18.8 b 0 a 6.3 b 27.8 b then acclimatized to greenhouse benches and Mean number of rootsw allowed to initiate new shoot growth.