Garden centers are borrowing a marketing strategy from the restaurant industry: super-sized plants.
Many growers have offered large-size containers of geraniums, bigger hanging baskets and an assortment of patio container plants, in particular, hibiscus. In the 1980s, plants originally grown only in flats started to appear in 6-inch and 1-gallon pots for summer sales. Instant color was the purpose of these large container-grown marigolds, petunias and impatiens. These plants were sold primarily in summer when consumers wanted large, finished plants. Of course, it was difficult for growers to keep flats of plants alive during summer, much less looking good, so the move to bigger containers was good for growers, too.
Since the late ’90s, the super-sizing trend has matured. Flats have become less common and large-size containers are produced year-round, even during the profit-critical spring season.
Unfortunately, growing plants in large containers takes more than extending production. Many annuals were bred to be compact. They look good in packs and small containers, but take a considerable amount of time to fill out 1-gallon or larger containers.
To identify plants for large containers, check out national field trials. Look for plants with a tall, mounding habit. Or, visit cut flower trials and look for well-branched plants with sturdy, stem growth.
Spring pots
Early spring starts with cool-season crops such as osteospermum, argyranthemum and snapdragons. One difficulty with cool-season cultivars is finding ones that grow well at low temperatures but do not collapse quickly as temperatures rise.
Delphinium
Delphiniums make great potted plants, especially the newer hybrids with a fast-growing, uniform and more dwarf habit. Three series have the classic delphinium colors of white, pink, lavender, purple and blue:
One plant can be grown in a 1-gallon container. However, since these cultivars tend not to branch much until after the first flower spike starts to open, three or more plants are best for larger containers.
Plants will be ready for sale in 17 to 20 weeks, with six to eight weeks of that production time as plugs. The flower spikes will probably still need support.
One potential problem is premature flowering, which results in small plants with short spikes. This can be caused by: holding plants for too long in the plug flat, water stress or temperatures above 77°F especially shortly after transplanting and high light levels.
Dianthus
PanAmerican’s Amazon series (Cherry, Purple, Neon Duo and Rose Magic) is a new type of dianthus similar to Dianthus barbatus, but it flowers the first year from seed without a cold treatment. It’s more vigorous and heat-tolerant than traditional D. barbatus. Plants will flower somewhat continuously, allowing for a long marketing period. The main stem will flower first in the shortest amount of time. If you want to market the plants at this stage, plant three or more per pot. One plant per pot can be used with containers larger than 1 gallon, but it will take longer to allow for the side shoots to develop flowers. Crop time will be 16 to 22 weeks, with five to seven weeks of the production in the plug.
Summer pots
Summer is the main season for large containers. Many species are suitable for summer sales and have been grown for years, including impatiens, marigolds, petunias, geraniums and dahlias.
Ageratum
The original ageratums were tall, gangly plants, which breeders tamed into short, mounding bedding plants. Cut flower cultivars are available, but they have too much of an open habit to be used as potted plants.
‘High Tide Blue’ and ‘High Tide White,’ from PanAmerican Seed, have solved the habit problem. They are taller and more vigorous than the bedding cultivars and are more floriferous and compact than the older cut flower types.
The vegetatively propagated ‘Cloud Nine White’ and ‘Cloud Nine Blue’ from Ball FloraPlant are also options. They are much shorter and more compact than the High Tide series but also very floriferous and durable. They may be useful for smaller containers. For very large pots, try ‘Blue Bouquet,’ ‘Red Top’ and ‘Blue Horizon.’
Banana
Bananas typify the tropical look that many homeowners are seeking. The large leaves are a striking addition to the landscape.
Many dwarf or semi-dwarf cultivars are best for pots. Cultivars with bronze foliage variegation, such as ‘Rowe Red’ and ‘High Color Mini,’ are especially attractive in containers. It is highly unlikely that consumers will be able to grow plants that produce bananas unless they’re grown in the
As with many tropicals, bananas are a bit slow to start in spring. They are best grown during the heat of early summer. From a plug, plants are ready to market in six to 10 weeks.
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Bob Lyons, director of graduate program at of
Plants produce purple, thistlelike flowers in the second year. In most cases, plants will be sold before they flower. They can be a bit slow to start filling out and grow best when night temperatures are above 60°F.
Kaempferia
This tropical plant, commonly called peacock ginger, is relatively unknown, but it definitely has its devotees because of its richly variegated foliage. Many species and cultivars are available, including large and compact types.
Three of the larger cultivars are ‘Raven,’ ‘Silver Diamonds’ and ‘Grande.’ ‘Raven’ has long, narrow, silver and green leaves with reddish-purple undersides. ‘Silver Diamonds’ and ‘Grande’ have large, wide, silver and green leaves.
Kaempferia grows best at night temperatures above 65°F. Don’t start the plants too soon as they won’t grow very fast until it gets hot. Outdoors, kaempferias require shade.
From a plug, plants in 8-inch pots will be ready to market in 13 weeks.
Rudbeckia
This native has now been bred for a short production period, prolonged flowering and a wide range of colors and flower styles. For large containers, ‘Indian Summer’ continues to be one of the best.
A more recent introduction, ‘Prairie Sun’ from Benary Seed, has two-toned dark- and pale-yellow petals with green centers and the same large flowers as ‘Indian Summer.’ In the greenhouse, plants can get a bit lanky, so growth retardants may be helpful. Crop time will be 14-20 weeks, with three to six weeks of that in the plug.
Sweet potato
With many plants, there is the concern that they won’t fill out the pot fast enough. This is usually not a problem with ornamental sweet potatoes. They are fast growing, fill out a pot well and love the heat, making them the perfect summer annual for large pots. Many very vigorous cultivars are available.
Bodger Botanicals released the Sweet Caroline series (Red, Bronze, Green, Purple and Light Green) bred at
The newest cultivars are in the Sweet Caroline Sweet Heart series. Plants produce heart-shaped leaves and have a more controlled habit. For a particularly unusual plant check out ‘Sweet Caroline Bewitched’ with its dark bronzy-purple, pointed leaves.
Plants finish in seven to 10 weeks for 8- to 10-inch containers starting with a rooted cutting. Ornamental sweet potatoes love the heat so don’t start them too early in the spring.
Zinnia
Magellan and Dreamland are two series that do well in big pots. They fill out fast with large, colorful flowers. Consider ‘Zowie! Yellow Flame’ and the large-flowered ‘Uproar Rose’ from Goldsmith Seeds. Both should only be grown in the largest containers.
‘Zowie! Yellow Flame’ is the most striking of the cultivars with medium-sized orange and red bicolor flowers. Around the center of each flower is a narrow band of rosy purple.
‘Uproar Rose’ has some of the largest, most heavily double flowers on the market and the color is a bright, uniform rose color.
Both Zowie! and Uproar cultivars can get tall and spindly in the greenhouse. Plan on using growth regulators or producing them outdoors on a container pad. Both cultivars are fairly mildew resistant but watch for the disease. Also, zinnias grown under short-day conditions produce more single flowers. Plants should be ready for marketing in eight to nine weeks from direct sowing.
Fall pots
Many fall crops have been grown in large containers: ornamental cabbage and kale, asters, and, of course, chrysanthemums. In recent years, companies have marketed large perennials with decorative fall foliage with some success. You may also want to consider ornamental vegetables.
Mustard
Red mustard ‘Red Giant’ is a foliage plant along the lines of ornamental cabbage. The bronze-colored leaves darken as the plants mature outdoors. The plants are edible.
Plants in 8-inch pots should be ready for marketing in six to eight weeks after sowing. Look for seed in the Asian vegetable section of plant catalogs and gardening Web sites rather than in the flowers section.
Swiss chard
This cool-season green has been grown for years. ‘Bright Lights,’ an All-America Selections Winner in 1998, raised its profile and many growers produce it as a fall ornamental. This cultivar has large, dark-green leaves with stems and leaf veins that range in color from yellow to orange to red. In large pots, multiple plants provide a lot of color.
This article is based on a presentation given by the author at the 2006 Southeast Greenhouse Conference in Greenville, S.C.
- John Dole
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John Dole is professor, North Carolina State University, Department of Horticultural Science, 158 Kilgore Hall, Campus Box 7609, Raleigh, NC 27695-7609; (919) 515-3537; john_dole@ncsu.edu.