Dept. of Horticulture, 245 Horticulture, Iowa State University, Ames, IA 50011



Dr. Diana Cochran
Dept. of Horticulture
Ph. 515-294-0035

ISU Research


Northern Grapes Project

The development of cold hardy northern grape hybrids based on Vitis riparia has allowed the expansion of the wine industry in the upper Midwest and Northeast U.S., and eastern Canada. In addition to improved cold hardiness, many of these V. riparia-based hybrids can exhibit very vigorous vegetative growth when grown on fertile soils, and have different fruit composition characteristics than V. vinifera and the more traditional interspecific French-American hybrids that present some challenges when making wine. These characteristics include a rapid rise in juice pHduring maturation coupled with the retaining of high levels of acids, high juice potassium, a different profile of malic to tartaric acid, and “herbaceous” characters in the wine.

In collaboration with 11 other institutions, Iowa State University is part of a 12 state USDA- SCRI Northern Grapes Project “Integrating Viticulture, Winemaking, and Marketing of New Cold Hardy Cultivars Supporting New and Growing Rural Wineries”. The ISU Department of Horticulture is part of the viticulture team whose goal is to improve the quality of wine produced from cold climate grape cultivars grown in sustainable vineyards located across the Upper Midwest and Northeast. The Department participates under the following objectives:

Objective1a: Evaluate cold climate cultivar performance under a wide range of climates throughout the Upper Midwest and Northeast to match cultivar with site.
Studies being conducted are using cultivars in the 2008 NE-1020 Multi-state Evaluation of Cold Hardy Wine Grape Cultivars.
Objective 2a: Evaluate crop and canopy management strategies to minimize fruit acid content and improve fruit composition in high-acid, cold climate grape cultivars.
A rapid rise in juice pH during maturation, retention of high acid levels, high juice potassium, a different profile of malic to tartaric acid and “herbaceous” characters in the wine that have been reported for cold hardy northern grape cultivars  have also been associated with grapes from overly shaded canopies.  The Northern Grapes viticulture team has undertaken studies to determine if cultural practices can improve fruit quality and winemaking potential of Frontenac, La Crescent and Marquette grapes.These studies include the evaluationsingle and divide canopy training systems, canopy management practices to improve light distribution, and crop load management.  Iowa studies include:

  • Training Systems: Frontenac and Marquette grapevines at Snus Hill Winery, Madrid, IA, and La Crescent grapevines at Hickory Creek Vineyard, Adel, IA were converted from a high wire cordon (HWC) to a Geneva double curtain (GDC), mid-wire cordon with vertical shoot positioning (VSP), and a Scott-Henry (SH) training systems.
    Training systems treatments (ppt slides)
    2013 Report
    2012 Report: 2012 was the conversion year and no data was collected.
  • Canopy Management Practices: Studies are being conducted on high wire cordon trained Frontenac and Marquette grapevines at Penoach Vineyard and Winery, Adel, IA and on La Crescent grapevines at Snus Hill Winery, Madrid, IA.  Treatments being evaluated includeall combinations of early season shoot thinning (thinning to a single shoot per node and removal of non-count adventitious shoots emerging along the cordon), lateral shoot removal (adventitious shoots emerging from the leaf axils) in the fruiting zone, and shoot positioning. Treatments were monitored for time required to conduct the various cultural practices, light distribution in the grapevine canopy, and fruit quality indices at harvest.  The study is be conducted by Dylan Rolfes, graduate student in horticulture.
    Canopy management treatments (ppt slides)
    2013 Report
    2012 Report
  • Crop Load Management: Studies to evaluate the influence of crop load on juice quality are being conducted on grapevines in commercial vineyards that are trained to a high wire cordon. Cultivars being evaluated include Frontenac at Snus Hill Winery, La Crescent at Hickory Creek Vineyard and Marquette at Penoach Vineyard and Winery.
    2012 Report: Grapevines at the sites were exposed to temperatures (F)in the low 20’s on April 11 when shoot development ranged from full swell to third leaf for Marquette; second leaf for La Crescent; and first leaf for Frontenac.  Some young Marquette vines were killed to the ground. With a limited crop, studies were delayed until 2013.
    2012 Spring frost injury (ppt slide)
    2013 Report

Objective 2b: Determine optimal mineral nutrition and soil management practices for cold climate grape cultivars. 
Unbalanced mineral nutrition due to a lack of or excessive nutrient inputs, particularly nitrogen or potassium, can lead to undesirable juice properties such as high or low acidity and sugars or low yeast assimilable N (YAN). Current mineral nutrient sufficiency ranges are based on other grape species (V. vinifera and V. labrusca) and they may not be appropriate for the new cold-hardy cultivars. There has been recent debate on whether or not petiole sampling is the best method to assess the nutritional status of grapevines.  To address these issues, the viticulture team is assessing the nutrition status of Frontenac, La Crescent and Marquette grapevines grower vineyards on different soils through soil sampling and petiole and leaf blade analysis, with the tissue sampling occurring three times during the growing season (bloom, four weeks after bloom and veraison). Correlations between mineral nutrient status, pruning weights, yield, and fruit quality parameters will be assessed.The study is being conducted in vineyards in MN, IA, SD, ND, and NY.  In Iowa, vineyards represent loess soils of western Iowa, heavier soils of southern Iowa, limestone soils of northeastern Iowa and glacial soils of central Iowa.

Presentations on the progress of the project team are reported at Northern Grapes Symposiums


2008 NE-1020 Multi-state Evaluation of Cold Hardy Wine Grape Cultivars
In conjunction with the Northeast Regional Research project NE 1020 “Multi-state Evaluation of Wine Grape Cultivars and Clones,” Iowa State University established a cold hardy wine grape cultivar trial in 2008 at the ISU Horticulture Research Station, near Ames, IA and at Tabor Home Vineyards and Winery near Baldwin, IA. The Iowa trialsare evaluating the performance of Corot noir, La Crescent, Marquette, Petit Amie, NY 95.0301-01, MN-1189, MN-1200, MN-1220, MN-1235, MN-1258, with Frontenac and St. Croix serving as controls. Similar plantings were established in South Dakota, Nebraska, and Missouri, with some selections being evaluated  Connecticut, Indiana, Kentucky and Michigan.The vines were spaced 8 x 10 ft apart (545 vines per acre) with three vines per replication, replicated six time in a randomized block design. Vines were trained to a high wire bi-lateral cordon system with the cordon wire at 6.0 feet.


Protein Expression in Cold Acclimating and Freezing Tolerant Grape Cane Tissues
Lee Goldsmith, graduate student, Gail Nonnecke, professor, Paul Domoto, professor, and Rajeev Arora, professor, Department of Horticulture
The continental climate in Iowa is important when selecting grape cultivars that are tolerant of low-temperature stresses. Many cold-regulated (COR) proteins respond to freezing stress, and are able to protect cellular membranes from cold-induced dehydration damage. It is unknown which proteins are important for cultivars to withstand extreme temperature fluctuations and low temperatures that can injure over-wintering canes. The objective of this investigation is to observe the ability of two grape cultivars to survive extreme temperature fluctuations during cold-acclimation, mid winter, and deacclimation. Experiments will be conducted to determine and compare changes in proteins during cold acclimation and deacclimation in canes for Frontenac and Seyval blanc grape cultivars.


Alternative Weed Management Strategies Influence Weed Control and Grapevine Yield in an Established Vineyard
Lisa Wasko, graduate student, Departments of Horticulture and Agronomy, and Gail Nonnecke, university professor, Department of Horticulture
Weeds compromise vineyard productivity by competing with grapevines for water and nutrients. Herbicides and/or cultivation are commonly used to manage weeds by viticulturists. However, these techniques may jeopardize soil sustainability and ultimately affect soil productivity. The need for economically viable alternative weed management strategies that are effective at managing weeds, maintain grapevine performance and quality, and conserve soil resources are of increasing concern. The first objective of this study was to evaluate the effects of four weed management strategies on weed control, grapevine physiological responses, and assayed soil parameters in an established vineyard. Secondly, this study will investigate the influence of irrigation on grapevine growth and development grown with or without a living mulch.

Influence of Cover Crop Rotation and Conventional Practices on Grapevine Plant Growth and Weed Growth
Dennis Portz, graduate student & Gail Nonnecke, professor, Department of Horticulture
Cover crops are used in rotation with cropping systems to improve soil quality and to suppress pests. Use of cover crops prior to replanting on sites with grape may provide a sustainable alternative to chemical pesticides and may maintain or improve soil quality. The objectives of this study were to investigate how cover crops affect weed and nematode populations and soil physical and chemical properties when used on replant sites with Vitis spp. (grape).

Weed Management and Soil Quality in Vineyard Agroecosystems
Craig Dilley (PhD candidate) and Dr. Gail Nonnecke, Department of Horticulture, ISU. Cooperators: Dr. Bruce Bordelon, Purdue University, Dr.Harlene Hatterman-Valenti, North Dakota State University
A project to examine the effects of conventional and alternative weed management systems on soil quality in vineyards in three states was initiated in 2004. Weed management treatments include: 1) conventional herbicide, 2) cultivation/tillage, 3) straw mulch, and 4) a living mulch of creeping red fescue ( Festuca rubra ). The goal of the project is to identify optimal weed management practices for soil quality and grapevine growth and development. A sub-objective of the project is to determine biological parameters that can be measured and used in combination with standard chemical and physical soil measurements to indicate an improving or declining condition of a vineyard soil. Data from the measurements will be normalized and incorporated into a mathematical index, called a soil quality index, to be used to gauge the level of an improving or declining soil condition.

2002 Leopold Center Grape Cultivar by Management System Trial

Through a grant from the Leopold Center of Sustainable Agriculture, a grape cultivar by management system trial was established in 2002 at the ISU Horticulture Research Station (Hort Station), and at the ISU Armstrong Research and Demonstration Farm (Armstrong Farm). The trial was designed to evaluate 15 cultivars under three management systems. In 2002, 10 wine cultivars [Maréchal Foch (Foch), Frontenac, Cynthiana (Norton), St.Croix, Chambourcin, Seyval Blanc (Seyval), La Crosse, Vignole, Traminette, Edelweiss], and four seedless table cultivars (Marquis, Vanessa, Reliance, Mars) were planted at the two locations, with the seedless cultivar Jupiter to be added in 2003. The three management systems being evaluated are a conventional system that relies on herbicides for weed control, and the application of insecticides and fungicides on a regular basis; an IPM/best management system that uses herbicides as needed, and relies on monitoring to determine the need for insecticides and fungicides; and an organic-approved system, that relies on alternative methods of weed control and the use of organic-approve insect and disease control strategies.

The vines were planted in mid-May. At each site, the vines were spaced 8 x 10 ft apart (545 vines per acre) with three vines per replication. Treatments were replicated five times at the Hort Station, and three times at the Armstrong Farm. Vines training will be to the bi-lateral cordon system on a 2-wire trellis with wires at 3.5 and 6.0 feet, and post spaced 24 feet apart. Vines with a procumbent (trailing) growth habit will be trained to the top wire, while those with a semi-upright to upright growth habit (Chambourcin, La Crosse, Seyval, Traminettee, Vignole) will be trained to the mid-level wire with catch wires added above.

2003 Wine Grape Cultivar Trial

Through an Iowa Department of Agriculture and Land Stewardship (IDALS) specialty crops grant awarded to the Iowa Grape Growers Association (IGGA), a wine grape cultivar trial was established in 2003 to evaluate the adaptability, productivity, and wine making quality 20 new cultivars and advanced selections at four locations in Iowa: ISU Horticulture Research Station, Ames; ISU Armstrong R & D Farm, Lewis; ISU Southeast R & D Farm, Crawfordsville; and ISU Northeast R & D Farm, Nashua. These sites represent three different climatic and four different soil conditions.
The vines were spaced 8 x 10 ft apart (545 vines per acre) with three vines per replication. The Crawfordsville and Nashua plantings included the cultivars being evaluated in the 2002 Leopold Center grape cultivar by management system trial. Treatments are replicated four times at each site (12 vines per cultivar). Vines training will be to the bi-lateral cordon system on a 2-wire trellis with wires at 3.5 and 6.0 feet, and post spaced 24 feet apart. Vines with a procumbent (trailing) growth habit will be trained to the top wire, while those with a semi-upright to upright growth habit will be trained to the mid-level wire with catch wires added above.

Cynthiana Grape Cultivar Propagation Study

‘Cynthiana’ (Norton) has shown promise as a wine grape for adapted regions of Southern Iowa, but unlike most grape cultivars, it is difficult to propagate from cuttings. Studies have found that rooting can be improved by treating the cuttings with rooting hormone such as indole-3 butyric acid (IBA). The use of bottom heat to simulate root development before bud breaks has also been shown to be beneficial. A student special studies project was established to evaluate the effect of bottom heat in combination with rooting hormone treatments on the rooting of ‘Cynthiana’ grape cuttings.

Horticultural and Chemical Practices Influencing Fruit Quality with ‘Reliance’ and ‘Swenson Red’ Grape Cultivars

Fresh table grapes can be grown successfully in the Midwest, and can add a new opportunity for agricultural diversification and local food systems. However, to be competitive, local growers will need to product high quality grapes to compete with out of state supplies. Practices that improved berry size, cluster appearance, or advance fruit maturation would increase the marketability of locally grown grapes. Gibberellic acid (GA3) has been shown to improve berry size in seedless cultivars and loosen clusters of seeded cultivars when applied at specific times. Practices that regulate crop load, such as cluster thinning and removing a portion of the cluster (tail thinning) have been shown to advance maturity of both seeded and seedless grapes. Tail thinning has also been shown to improve cluster appearance in some cultivars. This study was undertaken to evaluate these various practice to improve quality and advance maturity of seeded and seedless table grapes under Iowa growing conditions.


Grape cluster

Grape cluster.