Post-Production Quality of Bedding Plants

Dr. J. Raymond Kessler, Jr.

Auburn University

The post-production quality and garden performance of bedding plants purchased by consumers should ultimately be the number one concern of every segment of the Floriculture industry involved in delivering products to market. However, even casual excursions to a variety of retail outlets frequently results in disappointment with plant quality and how bedding plant products are displayed, maintained, and cared for. It has been estimated that about 20% of annual and perennial products entering the retail marked become unsaleable, damaged, or reduce in price. Losses in mass market outlets may be considerably larger. Rather than place blame however, growers and retailers should realize the importance of post-production quality to the survival of their businesses and work together to improve garden performance and marketability of bedding plant products.

The greenhouse environment is designed to provide optimum conditions for forcing bedding plants to grow and flower as rapidly as possible. However, conditions in the retail display and in the customer's garden are frequently the opposite and place plants under stress from a variety of sources. The responsibility of the grower, therefore, is to prepare crops for the rigors of the post-production environment.

Many decisions made by the grower in planning crop production and during the production process can have an impact on a product's post-production longevity. Careful crop scheduling so that plants are at peak quality at shipping time is important because overgrown, stretched plants quickly become unsaleable and are difficult to care for in a retail setting. Container size and the choice of media components can also impact keeping quality and garden establishment. A larger container volume retains more moisture for a longer period of time than small volumes which probably accounts for the popularity of jumbo packs in some markets. Water and fertility are used at luxury levels in the greenhouse to achieve the rapid growth rates necessary for production. However, overuse of these two inputs results in soft, succulent growth that does not hold up well on the retail shelf. Low light intensity for the bedding species being grown also contributes to soft growth and sends the product into the retail environment with low carbohydrate reserves. Applications of growth retardants not only improve visual appeal of the product but also increases the plants capacity to handle stress, mainly moisture stress. Lastly, any mishap or cultural error that reduces crop quality can also impact post-production longevity, e.g. nutrient deficiencies, insects or diseases, or physiological disorders.

Toning bedding plant crops in preparation for the market and home garden seems to have lost its appeal among all the high-powered techniques for forcing crops during production. However, toning requires only a short period of time at the end of the crop cycle and can significantly add to post-production keeping quality. Toning does, however, have to be included in crop schedules and crops must be arranged so that the toning environment can be applied at the proper time.

Growers manipulate plant growth during production by raising or lowering the day/night temperatures to speed-up or slow-down the progress of a crop. Reducing the night temperature prior to shipping has been shown to increase the shelf-life of many bedding plant species. Toning by reducing night temperature can be applied about the time of visible flower bud. However, reduce the night temperature by how much and for which species? It is well known that some bedding plants are more tropical in nature and do not tolerate low temperatures well while others are more adaptable. Thus, bedding plants can be divided into two groups for toning at different temperatures (Table 1).

Growers also increased or decreased fertility levels during production to provide a measure of control over plant growth rates. Some growers apply a last application of fertilizer to crops just before shipping, while others stop all fertilization a week or so before. Each of these practices may be harmful to crop longevity. Probably the best approach is to reduce fertilizer rates by about one-half near the end of the crop cycle.

Lastly, irrigation practices can be altered toward the end of the crop cycle to prolong post-production keeping quality. If crops have been grown at luxury moisture levels, increase the time between applications of water to tone growth. This does not mean allowing plants to visibly wilt, which can cause flower buds to abort and leaf drop.

Many foliage plants are exposed to light levels lower than those used in production to prepare them for the home environment. Lowering light levels to tone bedding plants in the greenhouse is probably not the right approach because it is more desirable to send the plants to the retailer with as high a carbohydrate reserve as possible.

Each of the toning strategies outlined above will make little difference applied alone, but can make a significant difference in improving post-production keeping quality when applied together. Toning at the end of the crop cycle combined with careful production planning and attention to detail during the crop could help growers produce products recognized by retailers and customers alike for superior quality.

Table 1. Tolerance of Bedding Plants to Cool Night Temperatures
Group A. Tone to 50 to 55F Group B. Tone to 58 to 62F
Ageratum Begonia
Alyssum Celosia
Calendula Coleus
Dianthus Impatiens
Marigold Pepper
Pansy Tomato
Perennials (all) Vinca
Petunia Zinnia

Adapted from A.M. Armitage. 1989. Color plants in the garden, increasing longevity of garden plants from seed to sale, p. 87-100. In: H.K. Tayama and T.J. Roll (eds.). Tips on growing bedding plants. Ohio Cooperative Extension Bulletin FP-763.