No abstract

The effectiveness of shade intensity and time of day in which irrigation was applied were tested for control of anthracnose symptoms caused by Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. on container-grown Euonymus fortunei (Turcz.) Hand.-Mazz. `Canadale Gold', `Emerald 'n Gold', and `Emerald Gaiety' during the 2002 and 2003 growing seasons. Rooted cuttings in 3.8 L containers were placed in 0% (full sun), 63%, 73%, or 80% shade at Park Hill, Okla., in 2002 and 2003 and at Stillwater, Okla., in 2002. Overhead irrigation was used to irrigate one-half of the plants in each cultivar and shade treatment in the morning and the other one-half during the afternoon. At both sites, disease damage ratings were inversely related to shade intensity throughout each growing season. Disease incidence was usually lower on afternoon irrigated plants than on morning irrigated plants. `Canadale Gold' typically had the most anthracnose symptoms followed by `Emerald 'n Gold'. `Emerald Gaiety' had the least symptoms regardless of shade intensity or irrigation time.

The objective of this study was to determine the most advantageous time to collect cuttings of Chinese pistache, a commonly recommended ornamental shade tree that is difficult to propagate by cuttings. In 1993, calendar date and degree days (daily mean temperature -7.2C) were used to estimate an appropriate cutting time. The greatest percentage of rooted cuttings occurred in male cuttings harvested on 13 May 1993 (397 degree days) and treated with 17,500 mg·liter-1 IBA or in male cuttings harvested on 20 May 1993 (482 degree days) and treated with either 8750 or 17,500 mg·liter-1 IBA. In 1994, cutting time was associated with calendar days, degree days, and morphology. The most rooted cuttings (44%) were from green softwood cuttings taken on 9 May 1994, which was 380 degree days from orange budbreak using a threshold temperature of 7.2C. Orange budbreak was characterized by separation of the outer bud scales such that the orange, pubescent inner bud scales were visible. Cuttings taken on 9 May 1994 and treated with 8750 mg·liter-1 IBA produced the most primary and secondary roots and the longest primary roots per cutting. Male Chinese pistache cuttings should be collected from green softwood or red semi-softwood stems when about 380 to 573 degree days have accumulated after orange budbreak. Chemical names used: indolebutyric acid (IBA).

Stem cuttings of rose-of-sharon (Hibiscus syriacus L. ‘Jeanne d'Arc’), barberry (Berberis thunbergii DC. ‘Crimson Pygmy’), juniper (Juniperus horizontalis Moench. ‘Plumosa Compacta’), and arborvitae (Thuja occidentalis L. ‘Woodwardii’) were rooted in substrates consisting of 0%, 25%, 50%, 75%, or 100% (by vol) perlite or expanded polystyrene beads with peat. Percentage of rose-of-sharon cuttings rooted and root ratings were lower with polystyrene than with perlite. Statistically, more barberry cuttings rooted with polystyrene (78.8%) than with perlite (78.3%), but the difference in rooting between polystyrene and perlite was not horticulturally significant. More juniper and arborvitae cuttings rooted with 50% perlite than with other perlite concentrations. Percentage of rooted juniper cuttings decreased but percentage of rooted arborvitae cuttings increased as polystyrene concentration in the substrate increased. More roots and longer roots formed on juniper cuttings with perlite than with the same concentration of polystyrene in the substrate. In contrast, arborvitae cuttings had more roots with 25% perlite than with 25% polystyrene, but arborvitae cuttings in 50%, 75%, or 100% polystyrene had more roots than cuttings in the same concentration of perlite. Results indicate expanded polystyrene is a reasonable substitute for perlite in rooting substrate for barberry, juniper, and arborvitae if appropriate ratios of polystyrene to peat are used.

Chinese pistache (Pistacia chinensis, Bunge.) is a commonly recommended landscape shade tree in the nursery and landscape industry. Currently, Chinese pistache trees are propagated commercially from seed, which results in highly variable branch habit and fall color. Mature Chinese pistache, like other Pistacia have proven difficult to root, graft, or bud successfully. This study was initiated to investigate the potential of mound layering as an alternative vegetative propagation method for producing genetically identical clones of superior mature Chinese pistache trees. Results from a greenhouse pre-trial in which trees were cut at two different heights and at three different morphological stages showed that significantly more shoots were produced when stock plants were cut 5 cm (2 in) above the soil line compared to 1 cm (0.4 in), and when trees completely broke dormancy before cutting. Field trials during two consecutive years evaluated four treatments consisting of 1) wound; 2) 17,500 ppm IBA; 3) wound and 17,500 ppm IBA 4) no wound, no IBA. In 1993, 77% and in 1994, 75%of wounded shoots treated with IBA produced roots.