During the winters of 1993–94 and 1994–95, 54 clones of Vaccinium angustifolium were evaluated for low-temperature tolerance of inflorescence buds. During both seasons, clones were tested periodically, starting right after leaf drop, continuing through mid-winter, and finally through spring loss of low-temperature tolerance. Plants showed greatest variation in lowest survival temperature (LST) during fall and spring sampling dates, and the least variation on the mid-winter dates. In the 1993–94 study, clonal LSTs for November buds ranged from –5 to –27C; January buds showed LST variation of 6C. April buds showed a similar trend to that observed in late November. LST variation is discussed relative to clonal selection for ornamental and commercial use.
Paul E. Cappiello
Lowbush blueberry (Vaccinium angustifolium) is a major fruit crop in costal, Northern New England and Atlantic Canada. One of the factors affecting production is low temperature damage of flower primordia. In addition to mid-winter damage, much of the damage occurs in spring due to late frosts. A study was designed to examine the seasonal variation in the LT50 of fruit buds and to determine the location of the tissue damage.
Field-collected stems were exposed to controlled temperature drops and examined for damage. Three types of damage were identified; destruction of flower primordia, browning of vascular tissue within the fruit-bud, and browning of stem tissue at the base of the bud. The seasonal variation of the occurrence of this damage will be discussed.
Paul E. Cappiello
The effect of a fish hydrolyzate fertilizer product on growth of Acer rubrum and Pseudotsuga menzeisii was studied. Bare root plants were fertilized at a rate of 90, 180, and 270 kilograms of N/hectare. Soil samples were collected every two weeks throughout the summer and were analyzed for nutrient content. In addition, August leaf samples were collected and analyzed for N, P, and K content. Growth measurements on Acer rubrum indicate that stem caliper was significantly increased by all fertilizer treatments over the control trees. The granular fertilizer produced a significant linear increase in caliper growth with respect to fertilizer rate. Shoot growth was also significantly increased by all fertilizer treatments; however, as with caliper growth, the granular fertilizer treatments resulted in the greatest and most consistent response. The response of Pseudotsuga menzeisii showed significant increases in shoot growth and stem caliper but results were not as consistent as in the case of the maple.
Paul E. Cappiello
For nearly 30 years, the Univ. of Maine has been conducting woody ornamental plant performance evaluations. While there are a number of focus collections under evaluation, the Rhododendron collection is one of the central features of the program. This report offers performance data for more than 100 specimens grown at the Lyle E. Littletield Ornamentals Trial Garden on the campus of the Univ. of Maine. Winter survival, folk disease rating, fall foliage color and effectiveness, and flowering dates are included.
John Wachter and Paul E. Cappiello
Terminal stem cuttings of Kalmia latifolia were collected from wild plants (Milford, N.H.) on 12 Nov. and transported on ice to Orono, Maine, for analysis. Samples were processed as follows: 1) stems wrapped in dry cheesecloth; 2) stems wrapped in moist cheesecloth; and 3) stems seeded with crushed ice and wrapped in moist cheesecloth. Prepared samples were subjected to freezing tests to a low temperature of –36C. Following two weeks of incubation at 21C, samples were evaluated for leaf, petiole, stem, and vegetative bud damage. Evaluation of frozen samples revealed: 1) stem tissue remained undamaged to –36C; 2) leaf damage was inconsistent across all handling methods, with no clear LST estimate, and ice seedinggenerally resulted in increased tissue damage; 3) LSTs for vegetative buds and petiole bases were –18C and –15C, respectively, and both yielded definitive and consistent results across all treatments. The results indicate bud and petiole tissue to be the best to use for future studies on LST estimates in Kalmia latifolia.
Paul E. Cappiello and Scott Dunham
Commercial lowbush blueberry production involves management of what have long been considered highly diverse populations of naturally occurring clones. Wide phenotypic variation evident in fields has often been anecdotally equated with variation in yield, cultural requirements, etc., however this has not been tested rigorously. Interest in selection of clones with superior low-temperature tolerance prompted this study to estimate population-wide variation within the species. Thirty six clones of Vacciniun angustifolium exhibiting most of the typical phenotypic classes were selected from two commercial production fields in Maine. Plants were evaluated for low-temperature tolerance of reproductive and vascular tissues on a monthly basis from November through April. In addition, variation in relative time of anthesis, flower structure, and floral low-temperature tolerance were determined. Results are discussed with respect to potential for selection of superior clones for both fruit production and ornamental use.
Paul E. Cappiello and John E. Preece
A single clone of Acer saccharinum was selected and propagated from each of 15 provenances across the plant native range. The clones were field grown in Carbondale, Ill., during the study period. Plants were sampled during Winter 1992-93 and 1993-94 and assayed for low-temperature tolerance. During both winters, plants exhibited greatest variation in tolerance around the November and April sampling dates. In midwinter, there was little variation observed and 13 of 15 clones were tolerant to at least -40C. The relationship among Acer saccharinum provenance and cold tolerance curves will be discussed.
John F. Wachter and Paul E. Cappiello
Stems of 33 varieties of Viburnum were screened for low temperature tolerance on five dates. Terminal stem cuttings were shipped overnight to Orono, Maine, from Oregon, Michigan, and Minnesota. Following a controlled freezing regime, stems were incubated for 7–14 days and evaluated for injury by visual observation. Lowest survival temperatures (LST) were estimated as the lowest temperature at which 100% of stems were uninjured. Varieties of V. dentatum, V. lantana, V. opulus, and V. trilobum were rated as consistently very cold tolerant. Viburnum ×pragense, V. dilatatum, and V. rufidulum were rated as consistently moderately cold tolerant. All V. tomentosum varieties showed inconsistent LST estimates. Varieties from the Oregon source were rated as cold intolerant. Direct comparisons by variety and source will be discussed with emphasis on consistent LST estimates. Rates of deacclimation as they occurred over the five testing dates will also be discussed.
Paul E. Cappiello and Scott W. Dunham
Seven Vaccinium angustifolium clones were tested for low-temperature tolerance over two dormant seasons. Flower primordia in the pseudoapical bud were damaged at higher temperatures than were stem tissue and primordia of the fourth floral bud. The flower primordia located at the stem tip also reacclimated earlier and seemed to show a stronger response to abrupt spring warming than did other tissues tested. Given the lowest survival temperatures determined and the ambient temperatures recorded, we recommend that the physiological and economic aspects of cryoprotectants and flower-delaying treatments be studied further.
John F. Wachter and Paul E. Cappiello
Lowest survival temperature (LST) estimations for 45 varieties of Magnolia from Delaware were obtained over 4 testing dates with some varieties tested on fewer dates due to a shortage of material. Terminal stem cuttings were subjected to a controlled freezing regime, incubated at 100% humidity for 10–14 days and evaluated for injury by visual observation. LSTs were estimated as the lowest temperature at which 100% survival was observed. LSTs were difficult to estimate due to a lack of consistency caused by fungal pathogens. Incubation in moist towels and aluminum foil, post-freeze addition of moist towels following prefreeze sodium hypochloride dip, and dry incubation were employed to eliminate fungal pathogenicity as a source of post-freeze damage. Results show varieties with M. ×loebneri heritage to be the most consistently cold tolerant. Varieties such as M. `Raspberry Ice' and M. `Merril' rated as inconsistent with no definite LST estimated. Direct comparisons of incubation method, date of test, fungal pathogenicity and varietal consistencies will be discussed.