Jason Grabosky and Nina Bassuk
In the development of a street tree planting medium for use as a sidewalk base, we have been testing a series of limestone gravel and soil media with varied amounts of clay loam suspended within the matrix voids. Tilia cordata and Quercus alba seedling roots quickly penetrated and grew in these systems when compacted to densities in excess of 2000 kg·m–3, while they were severely impeded in clay loam soil compacted to 1300 kg·m–3. Limestone mixes of the same design had variable, but consistently acceptable, California Bearing Ratios (>40) when compacted to similar densities; demonstrating their strength as a pavement base. Tilia root growth, based on the volume collected from total root excavations after two growing seasons, increased a minimum of 300% in the limestone mixes over the compacted clay loam control when the treatments were compacted to ≈80% Standard Proctor Optimum Density. Root penetration of Quercus increased >400% in the limestone mixes over compacted loam in a 6-month trial compacted to 95% Standard Proctor Optimum Density.
Anna Perkins Nina Bassuk
Budbreak inhibition and poor overwinter survival (OS) limit successful cutting propagation of Acer rubrum October Glory, A. rubrum Red Sunset, Hamamelis vernalis, H. virginiana and Stewartia pseudocamellia. Localized blanching (banding) of the cutting on the stock plant; a range of 3 IBA concentrations, and foliar spray application of: 1% silver thiosulfate(STS), STS followed ten days later by Gibberellin, GA4/7:250ppm(STS GA),50ppm thidiazuron (TDZ) and TDZ followed by GA4/7 (TDZ GA)were tested for increasing growth and overwinter survival.. Carbohydrates were analyzed in cuttings which did and didn't grow. A. rubrum October Glory*, and Hamamelis spp all had increased OS for cuttings which grew. A. rubrum Red Sunset demonstrated a similar trend. Hamamelis spp. had significant increase in carbohydrates for cuttings which grew. A. rubrum October Glory' exhibited the same trend. S. pseudocamellia did not have increased OS with growth. and showed no increases in carbohydrates with growth, but the cuttings that didn't grow had at least 93 % more carbohydrates than the other species analyzed. All species had higher OS when stored in the 3° C cooler, than in the fluctuating cold frame. Banding increased growth of A. rubrum October Glory, and H. virginiana. IBA concentration affected growth of all species. STS increased growth of H. virginiana and S. pseudocamellia. GA4/7 increased growth of all cuttings except A. rubrum October Glory.
Jason Grabosky and Nina Bassuk
CU soil is a material primarily composed of clay loam soil and crushed stone designed for use under pavement to promote street tree root growth in a durable pavement section, such as sidewalks or parking lots. One concern is the low total soil fraction from which tree roots can meet nutritive demands. At issue is the long-term nutrient management of street trees once the root zone has been rendered inaccessible due to the pavement wearing surface, although in 3-year field tests, there were no differences found between a CU soil material and an agricultural field control. CU soil treatments were produced in a fractional factorial design with a patent applied for, processed humate additive, a nursery production fertilization treatment, and a mycorrhizae inoculation package of Pt and various VAM species. The mycorrhizae/fertilizer treatment was eliminated for plant availability restrictions. Bare-root seedlings of Salix nigra Marsh. were grown in treatment containers for 5 months. A Minolta SPAD-502 was used to evaluate relative chlorophyll content as an indication of leaf tissue nutrient levels. Plant growth as a function of root dry weight, shoot dry weight, and shoot: root ratio was analyzed. Soil analyses were conducted on media samples collected at the end of the study to evaluate the impact of humate admixes in nutrient availability. The fertilization treatments positively influenced leaf color, shoot weight, root weight, and shoot: root ratio. There was no impact from the mycorrhizae inoculation on leaf color or growth. There was no impact from the humate additive on leaf color or growth. There were no additive effects found in the treatment levels.
Nina Bassuk and Peter Trowbridge
Creating the Urban Eden, a course taught jointly by faculty in Landscape Architecture and Horticulture at Cornell University, is a unique two-semester class spanning the academic year from August to May. Students face the task of creating viable, sustainable landscapes both in theory and practice. The success and sustainability of any planting design is ultimately dependent upon knowledgeable site assessment and analysis, appropriate plant selection, and clear communication of design intentions. This class teaches all aspects of landscape establishment, including detailed site assessment, woody plant identification, choice of appropriate plants, planting design, soil remediation, transplanting, and early maintenance in human-impacted landscapes. In addition to designing for a specific site, students learn about written specifications for technical planting and graphic details to communicate and implement design proposals. Every year on the Cornell University campus, the students in this class implement, in a hands-on manner, all aspects of landscape establishment that they have learned by creating new landscapes that serve to integrate theory, principles, practice, and provide a demonstration of fundamentals taught in the class.
Jason Grabosky and Nina Bassuk
CU soil is a material primarily composed of clay loam soil and crushed stone designed for use under pavement to promote street tree root growth in a durable pavement section, such as sidewalks or parking lots. One concern is the low total soil fraction from which tree roots can meet nutritive demands. At issue is the long-term nutrient management of street trees once the root zone has been rendered inaccessible due to the pavement wearing surface, although in 3-year field tests, there were no differences found between a CU soil material and an agricultural field control. CU soil treatments were produced in a factorial design with a patent applied for processed humate additive, and a nursery production fertilization treatment. Bare-root seedlings of Salix nigra Marsh, Platanus × acerifolia Willd., Ginkgo biloba L., and cell plugs of Ficus benjamina L. were grown in treatment containers for 5 months. A Minolta SPAD-502 was used to evaluate relative chlorophyll content as an indication of leaf tissue nutrient levels. Plant growth as a function of new growth dry weight was calculated. Soil samples were collected at the end of the study and were analyzed to evaluate the impact of humate admixes in nutrient availability. The fertilization treatments positively influenced leaf color and growth for all species. The CU soil control plants displayed significantly lower chlorophyll levels, but overall growth differences were less dramatic—insignificant in some cases. The humate additive did not consistently affect leaf color. The humate additive alone did not affect plant growth, but a significant positive interaction with the fertilizer treatment was evident for Platanus and Ficus. The positive interaction was insignificant in Salix and non-existent in Ginkgo.
Naalamle Amissah and Nina Bassuk
Two experiments were conducted to determine the effect of severe stock plant cutback on rooting in two oak species Quercus bicolor and Quercus macrocarpa using two propagation systems, layering and cuttings. In experiment 1, field grown plants were either cutback leaving a 0.04 m (1.6 in.) stump above soil level or left intact (not cutback) ≈1.7 m (66.9 inches) tall. Shoots arising from cutback treatments and intact plants were layered using a field layering technique and air layering respectively. Results showed significantly higher (p < 0.01) rooting percentages in layered propagules arising from severely cutback plants in both species [≈77% in Quercus bicolor and ≈70% inQuercus macrocarpa] compared with air layered shoots arising from intact plants [1% in Quercus bicolor and 0% in Quercus macrocarpa]. In experiment 2, shoots arising from three stock plant heights (severely cutback 0.04 m, cutback 1 m and intact ≈1.7 m plants) were either etiolated or grown in full light and cuttings rooted in a perlite medium under mist. Of the two species studied, propagule position was found to have no significant effect on rooting in Quercus macrocarpa cuttings, but significantly (p < 0.0001) influenced rooting in Quercus bicolor. Rooting was highest 59.3% in cuttings taken from cutback-etiolated stock plants. Comparing just the three cutback levels, rooting was highest (45.2%) in cuttings arising from 0.04 m stumps followed by those from 1 m stumps 7.5% and lastly intact plants 3.8%. The best rooting results were observed in shoots arising from severely cutback stock plants (0.04 m) using the field layering technique.
Nina Bassuk and Brian Maynard
The discovery and use of auxins in rooting and the development of mist propagation are unequivocal milestones in the history of propagation due to their broad applicability and effectiveness. Stock plant etiolation may prove to be in a similar class with these techniques. The practical use of stock plant etiolation to improve rooting in cuttings has largely been spurred on in the past 10 years by the successes achieved by Howard and others at the East Mailing Research Station, United Kingdom (9). For all the renewed interest, however, the practice of withholding light to improve propagation is probably an ancient one, having been employed every time a stool bed or layer was made or even a cutting inserted into opaque media.
Brandon Miller and Nina Bassuk
Impressive ornamental features including exfoliating bark and golden fall color are among the reasons why hickories [Carya (Nutt.)] are sought after by horticulturists. Their potential for application in the green industry continues to grow as producers and consumers in the United States become more interested in adopting native plants; however, an absence of knowledge that defines which species are tolerant of abiotic stresses in the landscape limits their use. If production of stress-tolerant hickories increases, they could be used to diversify urban forests and may bolster the resiliency of managed landscapes. We examined the predicted leaf water potential at the turgor loss point to estimate drought tolerance among several species of hickories and pecans adapted to growing in northern climates in the United States. Our hypotheses were that because some bottomland habitats experience seasonal drought in addition to flooding, taxa adapted to these sites may be more drought tolerant than previously assumed, and that the degree of drought tolerance would be variable within species and populations. Predicted mean leaf turgor loss measured in summer across species was −3.38 MPa. Kingnut hickory [Carya laciniosa (F. Michx.) Loud.] exhibited the lowest mean summer leaf turgor loss point −3.64 MPa), whereas pignut hickory [Carya glabra (Mill.) Sweet.] exhibited the highest (−3.20 MPa). Provenance of trees studied influenced estimated drought tolerance of C. laciniosa. Variability between individual trees within each species was observed, suggesting clonal selections of each taxon can be made for drought-prone landscapes. The results of this work imply that all the species studied are at least moderately drought tolerant and should be considered for planting in managed landscapes. Further, species often associated with riparian habitats may exhibit substantial tolerance to drought and should not be excluded from use on drought-prone sites.
Brian K Maynard and Nina L. Bassuk
New shoot growth of Carpinus betulus `fastigiata' was treated with stockplant etiolation and stem banding treatments and sampled for anatomical study at intervals over a 16-week period of greening following etiolation. Shading effects on the anatomy of the stem were also investigated. Numerous anatomical changes were noted with stem age and stockplant treatment. Among these were etiolation effects on the lignification of the secondary xylem, thickness of the periderm, and an increase in the percentage of sclereid-free gaps in the perivascular sclerenchyma, Stem banding increased the widths of the cortex and pith. Concomitant propagation studies revealed significant etiolation, shading, and banding effects on rooting percentages and root numbers. Using multiple linear regression methods rooting capacity was modelled best by linear combinations of the widths of the pith, non-lignified secondary xylem, cortical parenchyma and periderm, as well as the percentage of gaps in the sclerenchymatic sheath remaining non-sclerified. It is proposed that the development of sclereids in potential rooting sites reduces rooting potential. The exclusion of light during initial shoot development retards sclereid development by up to 3 months following treatment, which correlates well with observed increases in the rooting potential of etiolated and/or banded stems.