Cucumber (C. sativus L.) is a popular vegetable originating in India (Harlan, 1975), but grown throughout the world for centuries. The main types of cucumbers grown are American pickling, American slicing, Middle Eastern (Beit Alpha), European greenhouse (parthenocarpic), Asian slicer, and Oriental trellis. Cucumber types differ in fruit length, diameter, skin color, color uniformity, skin thickness, and skin surface texture based on their primary use (Wehner, 1989). Most cucumber cultivars have long vines and are grown flat on the ground or on trellis supports (oriental and greenhouse types). Pickling and slicing cucumbers are the two main types grown for commercial markets and home gardens in the United States; annual per capita consumption of fresh and processed cucumber was 2.9 and 2.2 kg, respectively in 2005 (USDA, 2005). In 2014, per capita consumption of fresh cucumbers was 3.1 kg (Statista GmbH, 2017).
Although cucumbers require a large growing area, vines can be trained vertically on a trellis to minimize space. Alternatively, gardeners may choose to grow dwarf, determinate, or compact cucumber cultivars that have shorter vines for patio containers or small garden spaces. These cultivars are sometimes categorized as compact or bush types based on their short internodes. Plant breeders make use of the determinate (de) gene for the dwarf habit because the bush (bu) and compact (cp) genes are associated with poor growth or abnormal seeds. Cucumber cultivars with dwarf growth habit include ‘Bush Whopper II’, ‘Picklebush’, and ‘Bush Champion’.
Cucumber plants can produce a combination of three types of flowers: staminate (male), pistillate (female), and perfect (male and female). Based on the type of flowers present, cucumbers are monoecious (staminate and pistillate flowers), androecious (staminate flowers only), gynoecious (pistillate flowers only), hermaphroditic (perfect flowers only), or andromonoecious (staminate and perfect flowers). Cucumber plants are normally monoecious, but most current commercial cultivars are gynoecious hybrid blends (88% gynoecious plus 12% monoecious pollenizer) or parthenocarpic (pistillate flowers only, and fruit set without pollination). Gynoecious and parthenocarpic cultivars usually have earlier and more concentrated yield, whereas monoecious cultivars will produce fruit over a longer period of time. An earlier and concentrated production period is preferred by commercial growers and processors, but may not be ideal for home gardeners. In a study conducted by Wehner and Miller (1985), three versions of the hybrid ‘Meridian 76’ (gynoecious × gynoecious, gynoecious × monoecious, and monoecious × monoecious) were similar in overall yield among the hybrids. The gynoecious hybrids provided an advantage in early yield (higher yield at first harvest), but had more grade No. 2 and cull fruit than the monoecious hybrid, possibly because of the high number of pistillate flowers pollinated and grown in a tight sequence.
Urban and container gardening are two of the fastest growing gardening trends in the United States (Crandall and Crandall, 1996; Mason et al., 2008). Urban gardening can occur at the individual or community level, stimulating economic development, creating green space, and providing a source of fresh vegetables, fruits, and flowers for local communities. Urban gardens have a beneficial effect on communities, and cities are starting to include these spaces in city planning (Colasanti et al., 2012; Freeman et al., 2012; Hunter and Brown, 2012). In addition to community gardens, container gardens provide a convenient alternative for the home-production of vegetables, fruits, and flowers. As the number of people living in apartments, condominiums, and townhouses increases, so does the number of potential container gardeners.
Despite the popularity of container gardening, information is limited on cultivars and optimal production methods for container-grown vegetable production. Internet resources are plentiful, but might not be based on scientific research. Universities continuously update their extension bulletins and services, but without home gardening studies they have been unable to make research-based recommendations. One such bulletin recommended the use of cultivar H-19 littleleaf, a tall, multibranched inbred with late maturity (Hopkins et al., 2008). This pure-line cultivar does have multiple branching and high yield, but its concentrated set makes it less appealing for many home gardeners. ‘Bush Champion’ is another popular cultivar recommended by extension specialists. In older (pre 2005) resources, many of the recommended cultivars have growth habits unsuited to container production or are no longer available. Also, the cultural practices in the literature are often vague and recommend various cultivars, container sizes, media types, fertilizer, and water regimes. One would hope that they were based on local production requirements.
In addition to limited information on production practices, plant diseases can be a hindrance for urban gardeners. Because of space constraints, home gardeners often use higher plant densities than university or commercial recommendations. Increased plant densities promote disease development. With the available chemical control options, there is a need for high yielding, dwarf, and resistant cultivars for urban gardens. Heirloom cultivars often lack disease resistance, and commercial cultivars with resistance may be unavailable. Two common diseases of cucumber are powdery mildew (PM) and downy mildew (DM) (Adams and Quesada-Ocampo, 2015; Ojiambo et al., 2015). These diseases often appear in mid- to late summer and affect the leaves of the plant. Powdery mildew, caused by Podosphaera xanthii, produces chlorotic spots on the upper leaf surface with an eventual white “powdery” appearance as the disease progresses. Downy mildew, caused by Pseudoperonospora cubensis, causes angular chlorotic lesions on the upper leaf surface (Ojiambo et al., 2015). Both pathogens can significantly reduce yield and fruit quality in field- or container-grown plants.
In urban gardening, container size is also an important factor. Cucumber roots grow 30–60 cm deep in field soil (Sanders, 1997). Inadequately sized containers result in small plants and may reduce fruit quality and yield. In addition, small containers can dry out rapidly, resulting in poor nutrient uptake, stressed plants, and reduced yield. Large containers are often preferred, but can be difficult to move and require a large amount of potting media. Various container sizes are recommended in extension publications from U.S. universities, including a 20–40 L container with one to two plants each (Crandall and Crandall, 1996), an 8–20 L container or hanging basket (Harrison, 1996), a container with one plant per 4 L of soil volume (Bass, 1999), a larger container for vining crops (including tall-indeterminate cucumber) than crops with bush habit with 16–20 L of potting medium per plant (Demboski et al., 2001) and 12–20 L per plant (Hopkins et al., 2008; Whiting et al., 2014).
The objectives of this study were to 1) determine the optimal cucumber cultivars of several types (dwarf vs. tall, gynoecious vs. monoecious, pickling vs. slicing) and planting density for use in containers and 2) evaluate field trials as a predictor of cultivar performance in containers.
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