Growers desire more techniques to control weeds in horticultural crops that are grown organically and consumed directly, such as red raspberry. Abrasive grit emited via high air pressure is a new method for controlling weeds. Grit derived from corn cobs was examined for its efficacy during the year of raspberry establishment for 2 to 3 years at three sites (seven site-years) and compared with efficacy of hand-weeding as well as no weed control. Grit was applied once or twice weekly after raspberry transplantation in spring until weed emergence ceased in mid to late July. Weeds and raspberry growth were assessed in August. Grit was effective in controlling broadleaf weeds, averaging 94% control across site-years, but control of grass weeds was less than 10%. Total weed (broadleaf plus grass) control across site-years ranged from 51% to 96% and averaged 78%. Raspberry cane growth was affected by weeds, and grit-weeding at least partially alleviated these effects. Thus, abrasive grit allows growers to manage broadleaf weeds effectively without herbicides or soil tillage. However, additional research is needed to determine the correct amounts and timing of grit applications, as well as more efficacious types of grit, to control grass weeds.

A new garden chrysanthemum with a shrub plant habit is released as a descendent of a cross involving two hexaploid species: Chrysanthemum weyrichii (Maxim.) Tzvelv. (female) × C. × grandiflorum Tzvelv. (male). Chrysanthemum × hybridum Anderson MN 98-89-7 [U.S. Plant Patent (PP) 14,495] is a vigorously growing shrub chrysanthemum for garden culture, exhibiting extreme hybrid vigor. Single daisy reddish-purple flowers cover the foliage in the fall, numbering >3000 on second-year plants. This selection displays excellent winterhardiness in U.S. Department of Agriculture (USDA) Z3b+ (–34.4 to –37.2 °C) as well as frost-tolerant flowers. In its second and subsequent years of growth after planting, MN 98-89-7 grows into a fall flowering (August–October), herbaceous shrub ranging in plant height from 61.0 to 91.4 cm with a diameter of 76.2 to 152.4 cm. Its spherical plant shape is achieved naturally with self-pinching, creating a highly manicured appearance; it also attracts honey bees and butterflies as pollinators. MN 98-89-7 is a vegetative product and this unnamed selection is being released for germplasm purposes as well as for potential licensing and naming.

Another new garden chrysanthemum phenotype, the groundcover or prostrate plant habit, has been developed by the public sector University of Minnesota, Flower Breeding & Genetics Program. Winterhardiness and flowering before a killing frost were the first traits introduced by the breeding program with ‘Duluth’ in 1939 (Clark, 1962; University of Minnesota, Minnesota Agricultural Experiment Station, 2014); introduction of winter-hardy cultivars and genotypes has continued unabated ever since. Fall flowering remains a popular trait of all garden chrysanthemum types (Anderson, 2006; Dole and Wilkins, 2005). ‘Duluth’ has an upright plant habit (cut flower); such cultivars have limited market share due to potential lodging and decreased flower coverage (Anderson, 2006). Later, the cushion plant habit was first developed in the 1950s– 1970s at the University of Minnesota with plant growth in a spherical shape and complete flower coverage during fall flowering (Langevin, 1992; Widmer, 1980). ‘Minn’ was the first cushion series on the market with ‘Minngopher’ (PP 4327) the first patented cushion cultivar (Widmer, 1978). Cushion plant habits now retain dominant market share of garden chrysanthemums across the United States and the globe, whereas upright (cut types) are second (Anderson, 2004, 2006; Anderson and Gesick, 2003, 2004; Kim and Anderson, 2006). More recently, the large, expansive ‘‘shrub’’ and cushion plant habit, characteristic of the Chrysanthemum ·hybridum Anderson ‘Mammoth ’ series (nine cultivars) reignited interest in garden mums, helping to move garden chrysanthemum market share from the no. 2 or 3 herbaceous perennial (behind Hosta and Hemerocallis) to the no. 1 ranking (Anderson, et al., 2015). Currently, garden chrysanthemums, Chrysanthemum ·grandiflorum Tzvelv. (syn. Dendranthema ·grandiflora Tzvelv.; syn. Chrysanthemum ·morifolium Ramatuelle) and Chrysanthemum ·hybridum Anderson, are the no. 1 herbaceous perennial in the top 15 U.S. producing states with a wholesale farm gate value of $117.54M in 2014 (USDA NASS, 2015). For the past several decades in the United States, garden chrysanthemum sales have exceeded the sum of both florist’s potted [$21.767 million (w)] and pompon cut flower chrysanthemums [$11.497 million (w)] (USDA NASS, 2015). The groundcover habit, exemplified by MN Sel’n. 90-275-27, is a genetically controlled, stable trait without the need for plant growth regulator or other chemical applications or hand manipulation to achieve the plant habit. The groundcover phenotype is characterized as horizontal growth of the lateral branches, creating a groundcover, wave, or prostrate growth form. In typical garden chrysanthemums, plant height:width follow a 1:1 ratio for cushion (hemispherical) types. In standard or upright garden chrysanthemums used as cut flowers (flowering only at the terminal branches), the height:width ratios = 1.5–2:1. Groundcover types exhibit height:width ratios of 1:3, 1:4, or 1:6. Groundcover MN Sel’n. 90-275-27 has a mean height:width ratio of 1:3.7, although it typically ranges from 1:1.7 to 1:3.2 or, in rare cases, 1:15.4 (Table 1). Groundcover chrysanthemums have lateral branches that grow horizontally along the soil surface in field and container trials (Anderson and Gesick, 2004; Gesick, 1997) and offer a genetic, rather than cultural, alternative to labor reduction. The effect of this growth creates a plant wider than it is tall. Thus, they differ from the cascade chrysanthemums used in botanic gardens for fall flowering shows, whose cascading effect results from downward vertical growth (negative geotropism) by training and pinching (Alfors, 1977; Bruckhaus, 1975; Miller, 1976). Cascade chrysanthemums are grown as hanging plants in large containers, achieving lengths of 1.8–2.1 m at flowering. Groundcover chrysanthemums may be useful in hanging baskets, rock gardens, large container plantings, and/or as edgings (Anderson and Gesick, 2004; Gesick, 1997). Given the increase in sales of petunias after the release of prostrate ‘Wave ’ petunias, e.g., $58.692 million (w) sales in petunia (flats only) for 1994 vs. $137.056 million (w; flats, potted, hanging baskets) for 2001 (USDA Statistics Board, 1995, 2002), a similar revolution could occur in the garden mum market with groundcover, prostrate, or wave-type cultivars. We have conducted container and field trials of groundcover chrysanthemums since 1990; creation of hybrid and inbred selections with this plant habit has been a major breeding objective since that time (Anderson and Gesick, 2004). In excess of 30 genotypes with the groundcover habit, covering all flower color classes (yellow, white, purple/ lavender, and bronze/red) and many flower types (daisy, duplex, semidouble, double, etc.) are contained within the breeding program.

hybridum Anderson garden chrysanthemum, 'Lavender Daisy' (U.S. Plant Patent No. 19,831), adds a new flower color to the Mammothä series, which are advanced interspecific hybrids from an open-pollinated cross between hexaploid C. weyrichii (Maxim.)Tzvelv.• C. •grandiflora Tzvelv.This cultivar is early-blooming (Week 32) and exhibits single to duplex daisy-type inflorescences with dark purple ray florets and gold disk florets with massive floral displays.'Lavender Daisy' is a USDA Z3b (-34.4 to -37.2 °C) winter-hardy herbaceous perennial with a tight cushion shrub phenotype.In their second and successive years, 'Lavender Daisy' plants form mammoth spheres 0.91 m tall and up to 1.16 m wide.Additional 'Lavender Daisy' traits are butterfly attraction, frost-tolerant flowers, and genetic ''selfpinching.''Mammothä 'Lavender Daisy' is clonally propagated, virus-indexed, protected by U.S. Plant Patent law, and available from Ball Seed Company, the exclusive North American licensee.

Mammoth™ ‘Twilight Pink Daisy’ (U.S. Plant Patent 14,455; Canadian Plant Breeders’ Rights Certificate No. 4192) is an interspecific garden chrysanthemum cultivar, Chrysanthemum × hybridum Anderson (= Dendranthema × hybrida Anderson) with common names of hardy mum, chrysanthemum, and garden mum. It is a new and distinct form of shrub-type garden mums in the Mammoth™ series with rosy-pink ray florets, a dark “eye” color in the center of the disc florets, frost-tolerant flower petals, and self-pinching growth. This cultivar is a butterfly attractant in the garden. Mammoth™ ‘Twilight Pink Daisy’ is a winter-hardy herbaceous perennial in USDA Z3b–Z9 (Southeast)/Zone 10 (West) with its cushion growth form displaying extreme hybrid vigor, increasing in plant height from 0.46 m in its first year to a shrub of 0.76 to 1.22 m in the second year and thereafter with greater than 3000 leaves/plant. Flowering is prolific, covering the entire plant at full flowering with as many as greater than 3500 flowers in the second year. Chemical abbreviations: ethanol (EtOH), indole-3-butyric acid (IBA).

Common groundsel is an important weed of strawberry and other horticultural crops. Few herbicides are registered for common groundsel control in such crops, and understanding and predicting the timing and extent of common groundsel emergence might facilitate its management. We developed simple emergence models on the basis of soil thermal time and soil hydrothermal time and validate them with the use of field-derived data from Minnesota and Ohio. Soil thermal time did not predict the timing and extent of seedling emergence as well as hydrothermal time. Soil hydrothermal time, adjusted for shading effects caused by straw mulch in strawberry, greatly improved the accuracy of seedling emergence predictions. Although common groundsel generally emerges from sites at or near the soil surface, the hydrothermal model better predicts emergence when using hydrothermal time at 5 cm rather than 0.005 cm, probably because of the volatility of soil temperature and water potential near the soil surface.