Fig. 1. Plume-flowered (var. plumosa) celosia are a popular bedding plant, but their summer production is increasing with the popularity of fall sales.
Photo: Christopher J. Currey

Celosia or cockscomb is a popular ornamental floriculture crop. While it is commonly grown as a cut flower, celosia is also a popular spring annual bedding plant. Recently, celosia has been increasing in popularity as a fall crop, sold alongside garden mums, flowering cabbage and kale, and ornamental peppers. This article aims to provide you with the tools to successfully produce celosia in the summer to expand your suite of flowering fall crops.

Cultivars and genetics

Popular celosia cultivars are all classified as Celosia argentea. However, there are three distinct varieties or "classes" of celosia — cristata, plumosa, and spicata. The cristata varieties have a large crest-shaped inflorescence, plumosa varieties have feathery plumes of flowers (Fig. 1), and spicata varieties have slender inflorescence spikes with a papery texture (Fig. 2). Plumed (var. plumosa) and spiked (var. spicata) celosia cultivars are the most popular classes grown as fall crops. There is a range of flower colors, from yellow and orange to red and purple. Additionally, new dark or purple-leaved cultivars are available. Popular seed-propagated varieties include ‘Dragon’s Breath,’ ‘Fresh Look,’ ‘Kimono,’ and ‘New Look,’ whereas ‘Intenz,’ ‘Kelos,’ and ‘Kelos Fire’ series are popular vegetatively propagated cultivars.

Propagation

Cuttings of celosia are easy to root, and can be direct-stuck into final containers. Rooting occurs between three and four weeks. Plug crops are usually between four and five weeks. It is not uncommon for celosia to flower prematurely in the plug tray or shortly after transplanting from the environment or culture during plug production. Premature flowering is caused by plugs being grown under inductive short days (more on this below), though this can be more problematic for plugs grown in the spring than in the summer. Moisture stress or allowing plugs to dry down severely in flats can also induce premature flowering. Aside from premature flowering, finished plant quality can be diminished if plugs are held in trays too long.

Fig. 2. New vegetatively propagated spike-flowered (var. spicata) celosia are a unique crop to include in fall mixes or other containerized color programs.
Photo: Christopher J. Currey

Flower induction

One of the keys to marketing celosia for fall sales is to have plants in full color. The majority of celosia are short day plants, but specific requirements vary across cultivars. Some cultivars such as ‘Dragon’s Breath’ have an obligate short day requirement and absolutely must be grown under short days to flower. Other cultivars have a facultative short day requirement and flowering happens more quickly when exposed to short days, though flowering will occur under long days. Some cultivars such as the ‘Kelos Fire’ series are day-neutral and flowering is unaffected by photoperiod.

For obligate or facultative short day cultivars, critical photoperiods range from 11 to 13 hours of light, and days longer than this can delay flowering. To inhibit flowering, day-extension or night-interruption lighting may be used. Alternatively, blackcloth can be used to shorten days. Plants started from seed or cutting after mid-May are not propagated under short days. After transplanting in late June or early July, flowering will begin in early- to mid-August, depending on the cultivar, in response to natural photoperiods. In order to not disrupt celosia flowering under natural short days, be sure there are no lights turning on in the greenhouse or outside that may interrupt nights.

Culture

The need to pinch is influenced by factors such as the number of plants per container or the type of propagative material. First, pinching will enhance vegetative growth and help bulk up containers. For larger containers, such as 6-or 8-inch or 1-gallon containers, multiple cuttings are used. For free-branching cultivars, such as the seed-propagated plumosa varieties, pinching may not be needed. However, pinching improves the vegetatively propagated spicata and plumosa varieties.

Celosia grows best with a general substrate pH, so target a pH of 5.8 (between 5.6 and 6.0). The nutritional requirements for celosia vary with propagative material. As seen when comparing seed and cutting varieties of other species, seed-propagated cultivars are lighter-feeding compared to vegetative propagated cultivars. Maintain a substrate electrical conductivity (EC) of 0.5 to 1.0 mS·cm–1 for seed-propagated varieties (100–150 ppm N) and 1.5 to 2.0 mS·cm–1 (250-300 ppm N) for vegetatively propagated varieties. The need for growth regulation depends on container size, cultivar, and seasonal weather. Chlormequat chloride, daminozide, and paclobutrazol are all effective, but specific concentrations depend on the degree of regulation required.

Take-home messages

Celosia are a familiar spring crop, but their colorful flowers and foliage can add variety and interest to your fall color programs. Selecting the right cultivars, minimizing stress during propagation, and managing daylength, summer production can lead to a high-quality crop. Try it — you just might fall for it!

Christopher is an assistant professor of horticulture in the Department of Horticulture at Iowa State University. ccurrey@iastate.edu