Impatiens wallerana Plants Grown With Controlled Release Fertilizer Perform Better When Planted in the Garden

  • Gladys A. Andiru and Claudio Pasian - Department of horticulture and Crop Science, The Ohio StateUniversity, Columbus, OH
  • Jonathan Frantz  - USDA-ARS, Toledo, OH
  • Michelle Jones - Dept. of Horticulture and Crop Science, The Ohio State University/OARDC, Wooster, OH

The use of controlled-release fertilizers (CRF) in greenhouse production can reduce environmental contamination and promote sustainability by supplying localized nutrients to the roots over a period of time. CRF use is a good step towards sustainability and improved nutrient-use efficiency in greenhouse crops.

CRF are not commonly used by floriculture greenhouse growers in the production of container crops. There are a few exceptions (e.g. poinsettias) where CRF are applied as a supplement to water-soluble fertilizers. More research is necessary to answers many of the questions growers may have before they expand their use of CRF to other floriculture crops like bedding plants.

One area that has been neglected in the scientific literature is the effect of CRF on the post-production quality of crops once they have been planted in the garden by consumers. Our experiments were thus carried out to evaluate the carry over effect of CRF on the performance of Impatiens wallerana.

Materials and methods

Greenhouse Phase

Impatiens wallerana plants were grown in 5-inch pots in the greenhouse with either Osmocote Plus 16-9-12 or 150 ppm N of a 20-10-20 Peter’s professional water soluble fertilizer (WSF). Plants were watered as needed using the same volume per plant of water or WSF solution. This volume was increased over time as plant size increased. One WSF treatment was hose irrigated without measuring the volume of solution applied.

The treatments consisted of:

  • CRF 5-6 month longevity (5-6 Month)
  • CRF 8-9 month longevity (8-9 Month)
  • A blend of both CRF longevities: 50% 5-6M and 50% 8-9M (Blend)
  • Hand-applied WSF with the same volume of water applied for CRF treated plants (WSF1).
  • WSF applied with a hand-held hose  (Control)

CRF was incorporated in the growing substrate at a rate of 6.8 kg·m-3 (5g/pot). At 54 days after planting, half of the plants were harvested for dry weight (DW) determination while the remaining plants were transplanted to the field.

Field Phase

Plants were transplanted to the field under shade (black shade cloth of 52% actual shade) and left to grow for 73 days during which irrigation was supplied as required. No additional fertilizer was supplied. The intensity of the green color was measured using a chlorophyll content meter Minolta SPAD meter. Consumers (38 people) evaluated the plant quality on a scale of 1 to 5 where 1 = disliked and 5 = liked most. At the end of the experiment, plants were harvested and DW was determined.


Greenhouse Phase

Visual inspection did not reveal any obvious differences between plants size/quality and fertilizer treatments. This observation has some value because that is what most growers will see when comparing plants grown with CRF and WSF. However, when dry weights were determined, plants grown with WSF were smaller than plants grown with CRF (Figure 1). The blend and 5-6M treatments produced the largest plants. All plants were of salable quality.

Figure 1.

Field phase

Plants grown with WSF and then transplanted to the field appeared smaller and slightly chlorotic (Figure 2).

Figure 2Figure 2Plants grown with the 5-6M CRF treatment had the darkest green color (Figure 3).

Figure 3Figure 3CRF-grown plants were much larger than WSF-grown plants, as indicated by their dry weight (Fig 4), and produced more flowers (Figure5).

Figure 4Figure 4 Figure 5Figure 5When consumers were asked to evaluate the plants in the field, they clearly preferred CRF-grown plants (Figure 6).

Figure 6


Growing plants with CRF not only produced larger impatiens plants in the greenhouse but it also resulted in better plants in the field. Studies to determine if other common greenhouse crops respond in a similar manner are underway. Furthermore, it has been shown in additional studies that CRF, when used in containers, can leach out less nutrients resulting in potentially a more sustainable way of growing crops because fewer nutrients are leached out of the containers. The carryover effect of CRF plus its reduced nutrient leaching can be used by growers as a marketing tool: better field performance and a more sustainable cultural practice.