Field-grown Cut Flowers Research Articles

Gibberellic Acid Shows Promise for Promoting Flower Stem Length in Four Field-grown Cut Flowers

Increasing cut stem length and reducing crop production time are producers’ goals for numerous cut flower species. One or both of these aims was met in several field-grown cultivars through foliar application of gibberellic acid (GA3), but effectiveness varied by cultivar, application rate, and timing. Of the 13 cultivars tested, stem length was increased in nine cultivars [Toreador Red celosia (Celosia argentea), Camelot White foxglove (Digitalis purpurea), Imperial Giants Pink Perfection larkspur (Larkspur hybrids), Compliment mix lobelia (Lobelia hybrids), Nippon Taka ornamental pepper (Capsicum annuum), Amazon Neon Duo and Bouquet Purple sweet william (Dianthus hybrids), Summer Pastels yarrow (Achillea millefolium), and Benary’s Giant Scarlet zinnia (Zinnia elegans)], and time to harvest was decreased in four cultivars [High Tide White ageratum (Ageratum houstonianum), lobelia, ornamental pepper, and zinnia], when GA3 was applied as a foliar spray. Concentrations of 400, 800, and 1600 mg·L−1 GA3 were most effective. Application of GA3 resulted in malformed or smaller flowers or lighter green foliage in foxglove, lobelia, sweet william, and zinnia. In most cases, only one application was tested, and greatest response to GA3 was observed during 3–6 weeks post application. Gibberellic acid did not influence stem length in three cultivars [High Tide White ageratum, Aurora Deep Purple delphinium (Delphinium hybrids), and Column Lilac Lavender stock (Matthiola incana)], and decreased flower stem length in one cultivar (High Tide Blue ageratum). Four cultivars were identified as good candidates for further research given their promising responses to GA3 treatments.

Evaluation of Variation in Time of Harvest Maturity of Flowering Shoots in Three Cultivars of Gentian

The time to harvest maturity of flowering shoots and the extent and source of variability in maturity dates differed among cultivars of gentian (Gentiana sp.), with a wider spread in time to harvest maturity in Showtime Starlet (41 days) than Showtime Diva (35 days) and Showtime Spotlight (29 days). Cultivars also differed by more than twice in their plant-to-plant variability in time to harvest. Although later-emerging shoots reached harvest maturity more quickly than earlier-emerging shoots, the use of growing degree-days (GDD) for this field-grown cut flower did not account for differences. For ‘Showtime Diva’, 77% of outliers reached harvest maturity at the beginning of the season (i.e., before the 10th percentile). For ‘Showtime Spotlight’, only 20% of shoots classified as outliers flowered early with the remaining 80% emerging late (i.e., after the 90th percentile). Strategies to control the spread in time to harvest maturity in late-maturing cultivars such as Showtime Starlet should focus on uniform shoot emergence and controlling temperature during growth. Although strategies to achieve uniform shoot emergence should also be targeted for ‘Showtime Diva’, controlling temperature during the growing season would not appear to offer significant control of the spread in time of harvesting floral shoots. However, in earlier-maturing cultivars such as Showtime Spotlight, strategies will primarily require a greater understanding of the factors influencing the variability in maturation of shoots within individual plants before, and after, emergence.

PRODUCING LATE-SEASON CUT LILY FLOWERS

There is growing interest in the production of field-grown cut flowers in the United States; this increased interest has raised new challenges for the floriculture industry. One of these challenges is to produce fresh cut lily flowers during the late summer and early fall months when demand remains high but availability has dropped. Procedures were developed to produce cut lily flowers from Oriental, Asiatic, and LA hybrid lilies during the late summer and early fall months. A mix of fresh Oriental, Asiatic, and LA hybrid lily bulbs were obtained from The Netherlands and frozen at -1°C upon arrival. Bloom time of the bulbs was staggered by thawing and planting the cold-stored bulbs at two-week intervals beginning at week 26 in June and continuing until week 30 in July. In addition to using frozen bulbs, fresh bulbs from the southern hemisphere were evaluated. In July, fresh lily bulbs of ‘Stargazer’ and ‘Helvetia’ were obtained from Chile. These bulbs had received eight weeks of refrigeration in Chile following harvest in May. The Chilean bulbs were planted every two weeks beginning the last week in July and continuing until late September to determine how late in the season a cut lily flower could be produced. The number of days to flower, the length of the flowering stem, and bud counts were recorded on all flowering stems. Genotypic and environmental differences were noted with all cultivars and several produced excellent cut flowers for late season harvest.

First Report of the Root-Knot Nematode Meloidogyne arenaria on Cheeseweed Mallow (Malva parviflora) in the United States

During a 2010 field trial for examining alternatives to methyl bromide soil fumigation for the production of field-grown cut flowers, weeds were collected for identification and evaluated for their potential as hosts for plant pathogenic nematodes. In one cut flower field located in Martin County, FL, six cheeseweed mallow (Malva parviflora L.) plants were collected that had root-galling typical of infection by a root-knot nematode (Meloidogyne spp.). Field collected plants were used for species identification of the weed and maintained in the greenhouse for seed production. Several gravid female nematodes were extracted from field collected mallow roots and individually identified as Meloidogyne arenaria based on their esterase phenotype (PhastSystem, GE Healthcare) (1). A single egg mass was then extracted from the field collected mallow roots and inoculated onto a tomato plant (Solanum lycopersicum, 'Rutgers') grown in steamed builders sand in the greenhouse. The single egg mass culture was increased for 8 weeks, until galling was sufficient to produce adequate nematode inoculum to complete Koch's postulates on the original mallow host. Ten mallow plants were inoculated with single egg masses originally isolated from mallow and increased on tomato. Ten additional plants were maintained in the greenhouse as uninoculated controls. Inoculated and control mallow plants were grown in the greenhouse for 8 weeks, after which the roots were evaluated for galling, and root-knot nematode J2 were extracted from roots and soil and counted. All inoculated plants produced galled roots and control plants did not. Gravid females were extracted from mallow roots and identified as M. arenaria based on esterase phenotype as previously described. Ten gravid females for each DNA extraction were collected from mallow roots and DNA was isolated with the PowerSoil DNA Isolation Kit (MO BIO Laboratories, Inc., Carlsbad, CA). Identification of M. arenaria was confirmed by using species-specific primers F5'-TCGAGGGCATCTAATAAAGG-3' and R5'-GGGCTGAATAATCAAAGGAA-3' (2) and F5'-TCGGCGATAGAGGTAAATGAC-3' and R5'-TCGGCGATAGACACTACAACT-3' (4), which produced single amplicon bands of the expected size of 420 and 950 bp, respectively. This weed species has been reported as a host for M. javanica in Algeria and as an experimental host in Egypt (3), but this report, to our knowledge, constitutes the first documentation of Malva parviflora as a natural host of M. arenaria. The importance of weeds as hosts for plant parasitic nematodes cannot be over emphasized. As growers, particularly in Florida and California, continue to lose tools for broad-spectrum pest control, the ability of nematodes to reproduce on uncontrolled weeds will become increasingly important.

First Report of Association Between Delphinium and Peziza repanda

Delphinium is a popular field-grown cut flower. In February 2004, a grower expressed concern about an abundant fungal growth. The fungus was identified as Peziza repanda. This fungus is common in nurseries that raise plugs on container media amended with wood material. Nursery growers should be aware of the potential for contamination of these media with spores of fungi commonly associated with wood. This report documents the first observation of an association between delphinium and an ascomycetous cup fungus. Accepted for publication 7 December 2004. Published 14 February 2005.

014 Weed Control and Productivity of Field-grown Cut Flowers

A set of studies was established in Summer 1998 to determine the tolerance of field-grown cut flower species to specific preemergence herbicides, the effectiveness of weed control by those materials, and to determine if productivity of cut flowers is affected either by the herbicides or by colored mulches. Pendimethalin provided excellent early season weed control, but poor late-season control. It consistently caused injury at 4 lb a.i./A and sometimes at the 2 lb a.i./A rate. Oryzalin provided good to excellent weed control, but slightly injured celosia and zinnia when applied at 4 lb a.i./A. Napropamide provided excellent early season weed control, but marginally acceptable weed control later in the season. Though napropamide caused some injury to celosia early in the season when applied at the high rate, no injury to any of the plants was observed later in the season. Prodiamine and trifluralin were the overall safest of the herbicides, but they provided the weakest weed control. OH-2 was very effective when placed on the soil surface, but was less effective when placed on an organic mulch. The organic mulch was designed to keep the OH-2 particles from splashing on to the crop plant and injuring the plants. OH-2 tended to be safer placed on a mulch than on the soil surface, but statice was slightly injured even when a mulch was used.

Field Production of Cut Flowers

There has been a recent resurgence of interest in the production of specialty, field-grown cut flowers. While field production of cut flowers is considered to be the development of a new cropping system by some, in reality it is a long-established practice. White (1915) stated in his floriculture textbook: “Previous to 1870 the flower growing business consisted principally of plants for outdoor bedding and for other ornamental purposes. The cut flowers of that period were mostly small-flowered and short-stemmed, such as heliotrope, camellia, tuberose and bouvardia.” Much of the current interest is in production and harvesting of plants previously grown as garden annuals and perennials; however, similar interest also occurred early in this century. White (1915) noted: “There is increasing interest among flower growers in annuals and herbaceous perennials which may be forced for cut flowers.” A list of recommended annuals and herbaceous perennials for cut flowers was published by Taylor (1916). There are several factors that limited field production of cut flowers in the United States. White (1915) states: “Greenhouses for the production of flowers are becoming more and more in demand in the south and west, while in many sections climatic conditions are such that cut flowers may be grown out-of-doors; still, the perfection of blooms, due to the better cultural conditions made possible under glass, and the consequent increased financial returns have encouraged growers to erect glass structures.” In 1930, more than four times the hectarage was devoted to field culture of cut crops than to greenhouse culture (U.S. Census Bureau, 1931). However, the average receipts per hectare for greenhouse-grown cut flowers were 40 times higher than those for field-grown material, although the cost of greenhouse production probably also was higher. Laurie and Ries (1950) published additional comprehensive lists of suggested herbaceous perennials for cut flower production, as well as lists of berry-bearing shrubs for cutting, flowering stems for cutting and forcing, and stems with colored bark for cutting. More recently, several extensive lists have been published on recommended plants for commercial field production of cut flowers (Seals, 1988), cut ornamental grasses (Meyer, 1988), cut grains (Godwin, 1988), cut wildflowers and weeds (Weiler, 1988), bulb crops (DeHertogh, 1989; Armitage, 1989) and woody plants (Dirr, 1989). In recent years, imports have seriously affected U.S. greenhouse production of cut flowers, the reduction changing from >50% of the total floriculture market in 1970 to < 20% in 1987. Two specific markets have been exploited by foreign producers: Dutch growers have captured significant U.S. market share by producing a wide selection of nontraditional cut crops, while the South Americans have captured substantial market share of the traditional florist’s crops (carnations, roses, and chyrsanthemums). The Dutch have gained market share by using cooperatives and extensive marketing programs. Several South American countries have a year-round climate well suited for production of several crops and much lower labor and overhead costs than U.S. producers. Mass marketers have gained a significant share of the U.S. retail cut flower sales, with Kroger now being the largest retail florist in the United States. The Kiplinger Agriculture Letter (1988) stated that “cut flowers and potted plants generated $28 per square foot per year ($301/m) in a supermarket, about twice that generated by fresh produce.” The market size and profit potential have led numerous entrepreneurs to attempt to find a profitable cut flower production and marketing system. In addition, many farmers are seeking ways to diversify their operations and improve profit margins. The predominant idea is that specialty annual and herbaceous perennial crops could be profitably grown in the field, avoiding the high overhead cost of operating a greenhouse. There are many species currently being field-grown with success across the United States for harvest as cut flowers. Some of the more popular and successful crops being produced are Dendranthema, Liatris, Gypsophila, Limonium, and Gladiolus. California and Florida have traditionally been the largest suppliers of fieldgrown cut flowers. Tjia (1985) stated that, in Florida, “new fieldgrown cut flowers such as gerberas, snapdragons, tuberoses, Asiatic hybrid lilies, Dutch iris, and calla lily are replacing more traditional field cut flowers such as spray carnations and chrysanthemums.” There are several critical factors that producers must address to determine their suitability to enter this market.

Postharvest Handling of Physostegia purpurea Cut Flowers

Physostegia purpurea Blake is a native, herbaceous perennial that has potential as a field-grown cut flower. Physostegia stems were harvested with one third of the florets open and were recut underwater in the laboratory. Fresh cut flowers treated with silver thiosulfate (STS) and held in a 2% preservative solution lasted 14 days, while control stems in deionized water (DI) lasted 6 days. Cut stems placed in darkness at 0C for 1 week had 8 days of vase life after removal from storage and treatment with STS and preservative, while stems held in DI after storage lasted only 4 days. Stems held dry at 22.5C and 43% RH for 8 hours before being placed in preservative had similar vase life as flowers placed in preservative immediately after harvest.