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Abstract
Root development of softwood cuttings from American elm, Ulmus americana L., seedlings was improved by aeration, misting, modified Hoagland’s solution, and the addition of KNO3, KH2PO4, and indole-3-acetic acid to the rooting medium. Cuttings from younger seedlings rooted more readily than those from older plants, and the basal portions rooted more readily than the terminals.
Abstract
Rooting of secondary softwood cuttings from 12-year-old American elm (Ulmus americana L.) was 38% from tops, 64% from stumps 2.0-2.5 m high, and 83% from stumps 0.3 m high.
Abstract
When Dutch elm disease (DED) was discovered in the U. S. in the early 1930's, programs were initiated to protect susceptible elms and to develop resistant elms for future use. Since the American elm, Ulmus americana L., was the most extensively planted species, seed collections were made throughout North America to find disease-resistant individuals. This search had only limited success and subsequent emphasis was placed on chemical control.
Abstract
Benomyl and thiabendazole (TBZ) fungicides incorporated into soil greatly depressed the growth of seedlings of American elm (Ulmus americana L.), marigold (Tagetes sp.), buckthorn (Rhamnus frangula L.), sycamore (Platanus occidentalis L.), and, to a lesser degree, silver maple (Acer saccharinum L.). Both chemicals were phytotoxic to sycamore. Pepper (Capsicum sp.), tomato (Lycopersicon esculentum Mill.), and bean (Phaseolus vulgaris L.), were less sensitive than the other species when grown in benomyl-treated soil. The growth of corn (Zea mays L.) and that of pea (Pisum sativum L.) were not affected. The growth of turfgrass was stimulated by benomyl. Neither benomyl nor TBZ affected the time of seed germination of American elm and marigold. Seedlings of these species, when transplanted to unamended soil, resumed normal growth. The activity of benomyl that had been incorporated into air-dried soil for 10 months was still high, but less than its activity in a fresh mix.
Abstract
Several desirable Ulmus species cannot be propagated by budding because their fine branching habit precludes obtaining buds with large enough bark shields. A twig grafting technique was used substituting 1-year-old dormant twigs 5-13 cm long, as scions in place of buds. In a greenhouse test in March-May, twig grafting was usually more successful than bud grafting. The success with twig grafts made in liner beds in June varied between 0-82.6% depending on the species and clone.