Author(s): James H. Brown
Where Published: Ohio State University, Ohio Agricultural Research & Development Center Special Circular 175
Date of Publication: 2000
Research Dates: 1989-2000
Subject Area: Investigation of the influence of soil/site factors and plantation management practices on the survival, growth and foliage characteristics of trees of a Canaan Valley West Virginia seed source of balsam fir (Abies balsamea var. phanerolepis planted in grower-owned plantations.

Summary: Seven-year-old trees (from planting) of a Canaan Valley seed source of West Virginia balsam fir planted at 34 locations throughout Ohio were evaluated to study the effects of soil and topographic site factors and plantation management practices on survival, grwoth and foliage characteristics of trees. Because of the size of plantings and/or variability in site factors within individual plantings, more than one evaluationw as made in some plantings, and a total of 102 individual plots were included in the study. Analyses showed that the type and effectiveness of weed control was the single most dominant factor affecting survival and tree characteristics. In those plantings without "effective" weed control (identified as annual applications of "residual" herbicides for at lest the first four years after planting), average survival of trees was approximately 13% lower, tree heights 45% lower, needle lengths and foliage weights 10% lowe, and foliar elements 10 to 16% lower. For plots that had received "effective" weed control, there was a complex combination of topographic and soil factors and, although there were general relationships between those factors and survival, growth and tree characteristics, statistical analyses to develop a mathematical soil-site equation for estimating growth and tree characteristics were not successful. However, a "subjective" planting guide (based on results of this study and data developed in other research by the author) was developed using different combinations of slope percent, slope shape, total soil depth, depth to soil mottling, and soil texture for evaluating the sustainability of sites for planting Canaan fir for Christmas Trees.

To obtain copies of this report, contact:
OSU/OARDC
Dr. James H. Brown
129 Williams Hall
1680 Maidson Avenue
Wooster, OH 44691
Phone: 330/263-3916
E-mail: brown.14@osu.edu

Author(s): Bert Cregg, MSU Department of Horticulture and MSU Department of Forestry; Jill O'Donnell, District Extension Forestry Agent and Christmas Tree ICM Agent; and Mel Koelling, MSU Department of Forestry
Where Published: Nursery, Landscape and Christmas Tree Research Projects and Educational Programs Date of Publication: December 2003
Research Dates: 2000-2003
Subject Area: Cone production in Abies fraseri

Summary: Heavy cone production is a frequent problem in Fraser fir (Abies fraseri) Christmas Tree plantations in Michigan. Unlike other members of the Pinaceae, cones of true firs (genus Abies) shed their scales in the fall and only the cone stalks remain. The cone stalks are unsightly and can reduce the value of Christmas Trees or render them unsalable. The number of cones on a given tree varies from none or a few to several hundred.

Besides reducing the aesthetic value of a tree, rapidly growing cone buds demand large amounts of the tree's energy reserves. In Christmas Tree plantations, growers typically remove cone buds within a few weeks of cone bud-break. When cone buds are less than 3 cm (1.25 inches) long they can be easily pinched off. However, cone picking must be done by hand and can require significant amounts of labor.

As part of an ongoing program to optimize production of Fraser fir for Christmas Trees in Michigan, we are investigating methods to eliminate precocious cone production. In this paper, the biology of cone production in firs, factors influencing cone production, and how these factors may be modified to reduce coning in Fraser fir are reviewed.

Biology of Cone Production
The development of cones in firs occurs in a two-year cycle. In year one, buds develop on the current-year's growing shoots. Initially, the buds are undifferentiated and may develop into vegetative (shoot) buds or reproductive (cone or pollen) buds. At about the time the shoots cease elongation, hormonal signals in the tree cause some of the developing buds to differentiate into reproductive buds.

These buds continue to develop over the first year but cannot be readily distinguished from vegetative buds. In the second year, cone buds grow and develop rapidly before the vegetative flush. Cones continue to mature and are pollinated in the summer, and the seeds are shed in the fall.

Factors Affecting Cone Production
Flowering in Abies appears to be even more inconsistent than in other conifers. While environmental and within plant control of conifer flowering is not completely understood, several factors are known to influence flowering. Our knowledge of these factors comes primarily from studies directed at improving flowering of conifers in seed orchard production.

Study results indicate hormonal relations, growth patterns within the plant, temperature, water availability, nutrition and tree size or age may influence cone production.

Hormones- Gibberellins are the hormones most consistently associated with flower production in conifers. Application of gibberellins increases flower cone production in a number of conifer species.

Cone crop cycles- Intervals between heavy cone crops vary from two to seven years for temperate members of the Pinaceae. In a study of forest trees in California, Abies concolor produced the most infrequent cone crops compared with Douglas-fir, ponderosa pine and sugar pine.

Temperature and water stress- Both temperature and water stress affect cone development. In the Pacific Northwest, researchers increased flower production in an Abies amabilis seed orchard by erecting small clear plastic tents over the trees during the late spring and summer.

Air temperatures inside the tents increased up to 14 degrees Fahrenheit above ambient. Placing tents over the trees increased the average number of cones per tree from 3 to 8 to 22 to 24 compared to related treatments without tents. Water stress and root pruning are also used in seed orchards to enhance flowering.

Nutrition- Flower production generally increases with improved nutrition, especially nitrogen and phosphorus. The form of nitrogen fertilizer is also important. Nitrate fertilizers may increase flower production up to ten-fold compared to ammonium sources.

Tree Age/Size- Most conifers do not produce significant cone crops until age 15 to 45 years. Among North American firs, fraser fir and balsam fir are considered the earliest to flower. In a test plantation near East Lansing, Mich., we observed cones on trees three years after planting as 2-3 seedlings (i.e. eight years from seed). We also observed extremely early (less than 8 years) flowering in Korean fir and Korean x Balsam hybrids in our exotic fir test plots.

Research Approaches to Reducing Flowering
Based on the developmental patterns of cones, we are investigating two approaches to eliminating cone production. First, we are evaluating the use of flower thinning agents commonly used in the tree fruit industry. These caustic chemicals cause fruit tree flowers to abort. Wilthin and ammonium thiosulfate are two products presently on the market for flower thinning of fruit trees.

In the spring of 2001, we initiated trials to evaluate the effectiveness of Wilthin to thin Fraser fir cones. Results from an on-farm trial in Ingham County, Mich., indicated that Wilthin at a high rate (8%) stopped the development of over 60% of the cones on treated trees. A second on-farm trial in Oceana County, Mich., yielded similar results in 2001.

In 2002 and 2003, the experiments were repeated at the on-farm site in Ingham County. In subsequent trials, Wilthin and ammonium thiosulfate did not stop cone development and we observed significant needle phytoxicity.

A second approach to eliminating cone production is to disrupt internal chemical signals that cause some undifferentiated buds on the current year's shoot to become next year's cone buds. From research on promoting flowering in seed orchards, we know that a hormone, gibberellic acid (GA), increases cone production in many conifers, including true firs. Several plant growth retardants used int he floriculture trade are GA inhibitors. These compounds retard growth of greenhouse crops by inhibiting GA synthesis or GA translocation.

In the spring of 2003, we treated 50 trees each with one of five PGRs. The trees were treated three times on a bi-weekly basis beginning when current year's short growth was nearly complete. The trees will be scored in the spring of 2004 for cone production.

Suggestions for Growers
Cone flowering in Abies is a complex process controlled by a variety of potentially interacting factors. Some standard practices in Christmas Tree culture may contribute to increased flowering. The typically high level of fertility maintained by growers may promote flowering. It seems unlikely that a single approach will completely eliminate flowering. However, growers may consider modifying cultural practices to reduce flowering.
1. Use ammonium sources of nitrogen rather than nitrate.
2. Irrigate trees to reduce moisture stress when buds are differentiating (current year's shoots are 50% to 100% elongated.)
3. Overhead irrigation, if available, may be used for cooling on warm days when buds are differentiating.
4. Flower thinning agents tested to date are not consistently effective and caused phytoxicity to needles.
5. Pruning reduces the number of cones per tree by reducing shoot length but does not affect ones per length of shoot.

To obtain copies of this report, contact:
Jill O'Donnell
Michigan State University Extension Service
401 N. Lake Street, Suite 400
Cadillac, MI 49601
Phone: 231/779-9480
E-mail: odonne10@msu.edu

Author(s): Melvin R. Koelling, MSU Department of Forestry
Where Published: Nursery, Landscape and Christmas Tree Research Projects and Educational Programs Date of Publication: December 2003
Research Dates: 2000-2003
Subject Area: Seedling growth in Pinus sylvestris

Summary: In recent years, Scotch pine popularity has declined. However, a sizeable market continues to exist. Management practices used by most growers require seven to eight years to produce the typical 6 to 8-foot tree preferred by most consumers. If growers could increase the height growth obtained in years one and two, the time period necessary to produce a marketable size and quality tree could be reduced by one to two years.

Aside from the obvious economic benefits (one year less of cultural and management costs) associated with producing a marketable size tree in a shorter time period, it is quite likely that a greater number of salable trees could be harvested per acre. Many growers experience significant losses in the number of harvestable trees as the age of the plantation increases due to degrading insect and/or disease problems. Shortening the rotation by one year would reduce exposure to and damage from these pests and an increase in harvest numbers would result from fewer trees being infested.

Materials and Methods
The purpose of this study was to determine the first, second and third year annual growth increments of six different size classes of Scotch pine seedlings and to determine annual height growth as a percentage of seedling size at the beginning of each growing season.

All stock was of the same seed source (French Blue) and produced under similar cultural and environmental conditions. The seedling stock size classes were: 18 mm Jiffy pellet; 28 mm Jiffy pellet; 42 mm Jiffy pellet; 160 styroplug; 1-0 seedling; and 2-0 seedling.

In late April and early May of 2000, three replications containing 15 seedlings each were established for each seedling size class at three separate locations. In late April 2001, four additional classes of seedlings (transplants) were out-planted at both the Manton and Sheridan sites. This material was also Scotch pine of the "French Blue" seed source. The classes of planting stock were: 160 styroblock plus 1 transplant; 36 mm plus 1 transplant; 42 mm plus 1 transplant; and 2-1 transplant.

Results
In early September of 2000, 2001 and 2002, measurements of total height were taken for all seedlings in each category. The objective of this study was to evaluate the amount of height growth in the first few years following planting for seedlings of different types and sizes.

Specifically, is the amount of annual height growth in the first couple of years following planting related to type and size of planting stock? While some of the results appear inconclusive, it is obvious that annual height growth percentages are larger for all Jiffy-type stock (18 mm. 28 mm and 42 mm) as opposed to other classes of seedlings. The one exception was the 1-0 seedling that grew an unexpected amount in the year of planting but declined in the following two growing seasons.

The average percentage height increase for the three different sizes of pellet stock was approximately 123%. The decline in annual height growth percentages for years two and three is most likely related to amounts and distribution of rainfall. In contrast to the 2000 growing season, both 2001 and 2002 were characterized by periods of drought. Drought conditions were present during the first part of the 2001 growing season but were particularly severe at both field locations throughout the entire spring and summer in 2002.

Additional height growth can be expected from a pellet-produced seedling as opposed to the conventionally used 2-0 material. This additional increase is particularly significant in the year of planting. While it is not suggested that smaller sized material (18 mm or 28 mm) be used for field plantings, the 42 mm materials can be expected to grow at a rate equal to or superior to 2-0 stock. Over the three-year period of this study, this stock (42 mm) increased by 960% from its original beginning height (2.63 to 25.26 inches). For the 2-0 seedling, the increase was 480% (6.49 to 31.16 inches).

The potential for greater height growth in the year of planting is clearly demonstrated. Demonstration of the increased first-year growth potential of pellet-produced seedling stock leads to some interesting possibilities regarding future seedling production. If a larger diameter pellet were used, e.g. 50 mm, and production conditions could be manipulated to produce a seedling with a greater height, i.e. 10 to 12 inches, it is highly probably that the rotation length necessary to produce a 7 to 8-foot Scotch pine could be reduced by one year.

The economic implications of this reduction in rotation length are obvious as total production costs would be lower. Additionally, exposure to some of the serious insect and disease pests (Zimmerman pine moth, pine gall rust, Diplodia tip blight, etc.) that are common in the latter years of the rotation would be lessened as well. This should result in a significant reduction in pesticide applications as well as an increase in the number of trees harvested per acre.

To obtain copies of this report, contact:
Jill O'Donnell
Michigan State University Extension Service
401 N. Lake Street, Suite 400
Cadillac, MI 49601
Phone: 231/779-9480
E-mail: odonne10@msu.edu

Author(s): John Hart, Rick Fletcher, Chal Landgren, Linda Brewer, Mike Bondi & Steve Webster
Where Published: Christmas Tree Lookout Date of Publication: Winter 2004
Research Dates: 2001-2002
Subject Area: Concern about declining tree productivity in fields with multiple rotations. Checked impact of young vs. old rotations for nutrient levels in sample trees.

Summary:

Methods
44 fields were sampled in the spring of 2001. They were segregated into old vs. new rotations based on soil chemical data, soil physical data, mycorrhizal evaluation and triazine residues. During late summer and early fall of 2002, needle samples were collected from 33 of the fields selected.

Results
No significant differences were found in mychorrizal and triazine levels. No single nutrient problem was evident in the study fields between young vs. old rotations. The increase in tissue manganese with rotation age is no likely responsible for decline in tree productivity. Some early and late rotation fields did produce trees with nutrient concentrations low enough to limit tree growth.

To obtain copies of this report, contact:
John Hart
Oregon State University
3017 Ag and Life Science Building
Corvallis, OR 97331-7306
Phone: 541/737-5714
E-mail: john.hart@oregonstate.edu