Potted Plants On CRFs

Controlled release series sponsors

After seeing how bedding plants are affected by controlled-release fertilizers, three separate studies were conducted to show how the use of these fertilizers influenced the production of potted plants.

The Poinsettia Experiments

Rooted liners of ‘Premium Red’ poinsettias were potted into 4.5-inch containers filled with a commercial soilless substrate that was amended with CRFs: Osmocote Plus 15-9-12 and Osmocote Plus 16-9-12 applied at a rate of 7.9 and 7.4 pounds per square yard (lbs./yd³), respectively, and Nutricote 20-7-10 at 5.9 lbs./yd³.

For comparison, a treatment of constant water soluble fertilizer (WSF) [15-4-15 Poinsettia FeED at 150 ppm nitrogen (N)] was also included.

The plants were watered using drip irrigation as needed throughout the experiment, and a leaching fraction between 20 to 25 percent was maintained and adjusted weekly to accommodate for plant growth. Total leachate was also collected from the treatments and analyzed for nutrients each week.

A second poinsettia experiment was conducted using larger containers and a range of CRF rates. Rooted liners of ‘Premium Red’ were planted in 6.5-inch containers filled with a commercial soilless substrate amended with Osmocote Plus 15-9-12 or Osmocote Hi-End 15-9-12 (both at rates of 3, 8, or 12 lbs./yd³), Osmocote Plus 16-9-12 at (2.8, 7.4, or 11.2 lbs./yd³) and Nutricote 20-7-10 at 2.2, 6 and 8.9 lbs./yd³. A constant WSF treatment (15-4-15 at 150 ppm N) was also included. In this study, plants were evaluated for growth and marketability.

The Growth Index of ‘Premium Red’ poinsettia was similar for all plants, regardless of fertilizer or rate used.


The Gerbera Experiment

Rooted liners of Gerbera ‘Drakensberg Daisy Apricot’ were potted in 4.5-inch containers filled with a commercial soilless substrate that was amended with different CRFs: Osmocote Plus 15-9-12 (7.8 lbs./yd³), Osmocote Hi-End 15-9-12 (7.8 lbs.yd³), Harrell’s 15-9-12 (7.8 lbs./yd³), Harrell’s 15.5-5.2-15.5 (7.6 lbs./yd³), Florikote 16-5-11 (7.4 lbs./yd³) or Florikote 11-3-12 (10.7 lbs./yd³).

A constant WSF treatment (15-4-15 Poinsettia FeED) was also included. Plants were irrigated as necessary while maintaining a leaching fraction between 20 to 25 percent. Total leachate was collected and analyzed weekly.

The Cyclamen Experiment

Rooted liners of Cyclamen ‘Laser Synchro Scarlet’ were transplanted in 4.5-inch containers filled with a commercial soilless substrate that was amended with CRF’s: Osmocote Plus 15-9-12 (3 or 6 lbs./yd³), Osmocote Hi-End 15-9-12 (3 or 6 lbs./yd³), Nutricote 20-7-10 (4.5 lbs./yd³) and Osmocote Bloom 12-7-18 (3.7 or 7.5 lbs./yd³).

Like the other studies, a constant WSF (15-4-15 Poinsettia FeED) was also included. Plants were irrigated as necessary while maintaining a leaching fraction between 20 to 25 percent. Total leachate was collected and analyzed weekly.

Similar Growth Index For Poinsettias, Gerberas and Cyclamen With CRFs

Plant height at flower and the average plant diameter of the finished plants were combined into one number that we called Growth Index (GI). The GI was obtained by adding the height to the diameter and dividing by two, which gives us a relative quality rating.

The GI of poinsettia and gerbera were all similar regardless of fertilizer or rate used. Only cyclamen fertilized with Osmocote Plus 15-9-12 at 3 lbs./yd³ had a significantly lower GI than the WSF treated plants. Poinsettias in the first experiment were of similar total height regardless of fertilizer treatment.

Poinsettia plants treated with Osmocote Plus 16-9-12 and Nutricote 20-7-10 had lower dry weights than the other treatments. Osmocote Plus 16-9-12 and Nutricote 20-7-10 are labeled to have five-to-six month and seven-to-nine month release rates, respectively.

Gerbera ‘Drakenberg Daisy Apricot’ also had a similar Growth Index for all plants, regardless of fertilizer or rate used.


In both cases, it is probable that the plants were not receiving adequate nutrition early in the crop cycle, during the period when most growth occurs due to the release rate of these two products. During the second poinsettia experiment, all CRF-treated plants began to show mild symptoms of nitrogen deficiency during the last three weeks of production. The plants were treated with several applications of WSF and symptoms disappeared.

When the amount of nitrogen leached between the WSF and CRF treatments is compared, the environmental benefits of using CRFs is clear. The amount of nitrogen in the leachate continued to increase dramatically through the production period for WSF, while for CRF the amount of nitrogen in the leachate was much less, declining over time auntil it was barely detectable after six weeks.

Consider More Than Just The Per Bag Cost

Cost is always an important aspect to consider when evaluating a new product or production procedure. Many growers have indicated that the price of CRFs is too expensive to even consider using them in the greenhouse. That is a reasonable reaction when you consider that a 50-pound bag of CRF can cost around $100 and a 25-pound bag of water soluble fertilizer costs around $30 to $40.

In terms of dollars per pound of nitrogen, CRF is more expensive; however, it is important to factor in the overall cost of fertilizing the crop, not just how much the material costs. For our poinsettia crop, over the course of the experiment, we used 6.8 liters (1.8 gallons) of water.

When the cost of WSF is calculated (considering fertilizer is applied at every irrigation), it costs about $3.26 to fertilize 100 containers when the fertilizer costs $40.35 for a 25-lb. bag. At the application rates used, the CRF treatments cost between $0.70 to 1.03 for 100 containers when the CRFs cost $100 for a 50-pound bag.

Trial CRF Products For Best Results

CRF fertilizers show great promise for potted flowering crop production. Cost per container is drastically reduced and the amount of runoff is also reduced. Although in most cases growth was similar to constant WSF, there were some symptoms of nutrient deficiencies —mainly nitrogen.

As suggested in the first article in this special report, it is recommended that growers gradually transition to CRFs and use a combination of WSF and CRF. An alternative is to apply WSF to green up plants before they are sold or as soon as nutrient deficiencies are observed. Not all CRFs are coated in similar ways, and this will affect the release rate of nutrients. Therefore, it is important for growers to conduct their own trials to determine how their crops respond to different rates and different CRF products.

Leave a Reply

More From Fertilization...

July 31, 2015

All-America Selections Promotes Garden-Fresh Cooking

All-America Selections (AAS) has stepped forward with another first when promoting AAS Winners, this time in the form of cooking videos using vegetables/edibles that have performed extremely well in the AAS Trials. These days, a love of gardening is directly related to a passion for cooking. Tying the two together is a natural when marketing joys of cooking with fresh vegetables from the garden and farm market. After 82 years of conducting trials where only the best performers are declared AAS Winners, the organization now has more than 325 individual varieties that have been “Tested Nationally & Proven Locally.” It is some of these many varieties that culinary storyteller, entertainer and horticulture industry veteran Jonathan Bardzik will use in a series of five videos demonstrating cooking techniques with AAS Winning herbs and vegetables. “I am excited to partner with All-America Selections to show people across the country that AAS Winners perform […]

Read More
Burpee Home Gardens Brand Adds Flowers

July 31, 2015

4 Reasons Retailers Snub National Brands

Greenhouse Grower’s lead editor, Laura Drotleff, and I got into a debate about why garden retailers, especially independent garden centers, snub marketing efforts from breeders and growers. She was very much on the breeders’ and growers’ side, expressing frustration about how limited retailers’ vision can be on the topic. I’ve reported on the garden retail side of the industry since 1998, about the same length of time Laura has reported on growers. I’ve heard a lot of retailer views on this, so allow me to share the most common reasons why retailers decline free marketing: Costs. While the marketing materials are free, and sometimes advertising, participating in these projects usually requires minimum orders. From a grower’s perspective, the minimum orders are reasonable. If garden stores promote a plant line, they need to have enough supplies to satisfy demand. From a retail perspective, if inventory reports show a plant line can […]

Read More
llan Armitage Syngenta Starcluster

July 30, 2015

Let’s Talk About Starflowers. Why Is Pentas Not More Popular?

It is good to talk about production techniques, performance results and then to see how our friends garden. Diversity of plant material has always been a strength in American garden centers, and we should never run out of plants to get people excited. However, perhaps people are tired of Petunias or Callas or Geraniums, but we will never run out of options to put in front of them. One plant that is often overlooked is Pentas, a fabulous summer crop for late spring sales. These are heat-tolerant plants, and growing them below 65°F in the greenhouse results in significant delay. Fertility should be at least 150ppm nitrogen, but avoid ammonia in the fertilizer. Plants are best grown at a somewhat higher pH than usual, between 6.4 to 6.8. For best presentation, pinch out the center bud. Side flowers will bloom together, and plants will walk off the shelf. Garden centers […]

Read More
Latest Stories

June 13, 2015

UMASS Fertilizer Trials Recommend Nature’s Source Organ…

In a recent online fact-sheet at its Extension website, the UMass Amherst Center for Agriculture, Food and the Environment lists Nature’s Source Organic Plant Food 3-1-1 as “the best liquid organic fertilizer,” according to Dr. Douglas Cox, Stockbridge School of Agriculture. It is called-out by the Extension after a number of years of studying the use of organic fertilizers for growing commercial greenhouse crops. The trials evaluated traditional water soluble and granular slow-release chemical fertilizers. Dr. Cox recommends Nature’s Source Organic Plant Food 3-1-1 as a liquid fertilizer that is readily available, cost effective, OMRI-listed and with good label directions for greenhouses. He also mentions the ease-of-use in how it mixes well with water and can pass fertilizer injectors. “Nature’s Source is currently the best liquid organic fertilizer,” Cox wrote in his article “Organic Fertilizers – Thoughts on Using Liquid Organic Fertilizers for Greenhouse Plants,” “I have seen no foliar chlorosis yet with this fertilizer. Nature’s source is widely available and a great […]

Read More

January 9, 2015

6 New Fertilizer Products For Healthy Plants

These five products add even more options for delivering nutrients to the root zone.

Read More

January 7, 2015

Fertilizers And The Future

As growers look for new ways to cut costs and conserve resources, fertilizer and equipment companies are offering products that strive to save water, reduce toxic runoff and keep chemicals out of the equation.

Read More

December 31, 2014

Gain Greater Control Of Fertilizer With Automated Ferti…

University researchers look at integrating irrigation and fertilization with the help of water sensors to reduce fertilizer treatments and improve application timing.

Read More

October 30, 2014

Basics & Beyond: Comparing Substrate Fertilizer Ame…

Cornell University researcher determines if substrate-incorporated slow-release fertilizers can be used to replace or reduce the need for liquid fertilizer for four spring crops.

Read More

July 24, 2014

Using Controlled Release Fertilizers To Produce Garden …

Researchers determined whether or not garden mums can be grown with controlled-release fertilizer, and if it reduces fertilizer leaching, as compared with water-soluble fertilizers.

Read More

March 14, 2014

New Foliage Pro Fertilizer Offers Complete Nutrition Pl…

Dyna-Gro Nutrition Solutions has developed a process it says is capable of keeping all 16 essential plant nutrients in solution form.

Read More

January 30, 2014

OASIS Grower Solutions Introduces New One-Bag Hydroponi…

The new 16-4-17 Hydroponic Fertilizer from OASIS Grower Solutions (OGS) is a one-bag solution that replaces two-part systems traditionally used by commercial hydroponic growers. It is specifically formulated for commercial hydroponic production of lettuce, herbs and vegetables.

Read More

December 30, 2013

Fertilizer Changes Growing Mix pH

When considering a fertilizer's influence on media pH, you need to know its acid or basic reaction.

Read More

December 30, 2013

Basics & Beyond: Fundamentals Of Phosphorus Nutriti…

Phosphorus is an essential element, after all.

Read More
Everris Liquid S.T.E.M.

December 30, 2013

New Fertilizers For 2014

New fertilizer products not only deliver optimum nutrition, they also provide for easier application and increased efficiency. Check out these new products to help your operation produce a healthy crop in 2014. Click through on the pages below.

Read More

December 18, 2013

Focus On Fertilizer: Micronutrients And Organics

New fertilizer products are focusing on micronutrients and providing efficient options for organic production.

Read More

August 27, 2013

BioWorks Adds EcoVita To The Verdanta Family Of Biofert…

EcoVita, a homogeneous granular organic fertilizer, has been added to Bioworks Inc.’s Verdanta biofertilizers product family. This fertilizer will be manufactured and supplied to BioWorks by DCM Corporation of Belgium, a producer of natural and organic-based fertilizers in Western Europe. EcoVita is suitable for a wide variety of crops with its gentle release curve including:• Organic fertilization as a base nutrition in potting mixes• Leafy vegetables• Fruiting vegetables (s a top dressing) • Roses and other ornamentals The new fertilizer offers long-lasting and continuous action for 75 to 100 days and contains organic phosphorus (5 percent P2O5) for fast rooting. Nutrients in EcoVita are gradually released by the soil microbes, in addition to producing humus for better rooting and less leaching. EcoVita is OMRI Listed, making it suitable for use in organic production. “We’re pleased to introduce EcoVita 7-5-10 as our organic NPK product to complement our organic products: K-Vita 2-0-20 […]

Read More

April 29, 2013

Rockwell Farms Introduces Ready-To-Pour Container Ferti…

Rockwell Farms has introduced Rockwell Farms Plant Food, a bottled liquid fertilizer that does not need to be diluted before use. Always looking for ways to help the consumer succeeed, Jason Roseman of Rockwell Farms says the operation is also always looking for ways to get consumers to come back and buy more plants and flowers. “We feel like fertilization is one of those things that can be very confusing,” Roseman says. “Not everyone does it, and not everyone knows what they’re supposed to do.” The solution: Rockwell Farms Plant Food. The formulation is 150 ppm of a 20-10-20 fertilizer and is sold in 24-ounce bottles. Rockwell recommends that one bottle be used to fertilize 1.5- to 3-gallon outdoor plant and flower containers every 21 days. The product’s signage shows a young patio gardener pouring the bottled fertilizer on a windowbox with the tagline, “Just pour on your way out […]

Read More

April 29, 2013

Plant Products To Be Purchased By MGS Horticultural And…

MGS Horticultural Inc., a full-service supplier of fertilizers, pest control products, seeds and substrates in North America, together with Haifa Chemicals, a global supplier of potassium nitrate for agriculture and industry, specialty plant nutrients and food phosphates, today announced a plan to purchase Canadian fertilizer and pesticides supplier Plant Products Co. Ltd. The deal is anticipated to close by the end of June 2013. MGS will acquire Plant Products’ Canadian distribution business, sales force and name. MGS plans to use both names (MGS Horticultural and Plant Products) in all communications going forward. MGS will maintain locations in Leamington, ON; Brampton, ON; Laval, QC; St. Hyacinthe, QC; and Detroit, Mich. As part of the deal, MGS has signed multi-year agreements with Haifa to maintain exclusive distribution of Plant-Prod Soluble Fertilizers, Acer Controlled Release Fertilizer, Stim-Root and potting soil premix fertilizers for distribution in Saskatchewan, Manitoba and Eastern Canada. “MGS is excited […]

Read More

March 19, 2013

Irrigation And Fertilizer Tips For New Vegetable Grower…

Compared to other variable costs, fertilizers are not the largest part of the budget in conventional greenhouse production. Nevertheless, over the course of the season, mistakes in fertilizer use can lead to significant damages or crop losses. That makes this an important topic for ornamental growers who are experimenting with growing vegetable crops. This article will emphasize major differences between fertilizers used in vegetable production and in ornamentals production. The different nutrition strategies, monitoring and water volume per plant will also be explained. Fertilizer In ornamental production, nutrients are delivered using various water-soluble fertilizers through a fertilizer injector, through the use of controlled-release fertilizers, or a combination of the two. There are numerous fertilizer mixes available with all the needed nutrients already included. The fertilization rate is often given in parts per million (ppm) of nitrogen (N), which is a way of expressing the fertilizer concentration. At younger stages, plants will […]

Read More

March 11, 2013

Daniels Plant Food Rebranded As Nature’s Source

Ball DPF has announced the launch of Nature’s Source, a rebranding in name and packaging for its seed extract-based plant fertilizer product Daniels Plant Food. The new brand will make its industry debut at California Spring Trials. “While we are proud of our heritage, we made this bold decision because we’re expanding sales to our existing market segments and entering new ones. It was a good opportunity to start with a fresh name and a modern look for all our products and packaging,” says Chance Finch, general manager for Ball DPF. “We wanted to make it obvious, beginning with our Nature’s Source brand name, to know our products are sourced from nature. Growers, contractors and gardeners can be confident that our effective and unique formulations remain unchanged. We’re excited about launching updated packaging for all our products, and especially the new ready-to-spray plant food for home gardeners.” The Nature’s Source brand […]

Read More

March 6, 2013

Everris Introduces E-Max Release Technology Coating Che…

Everris has introduced its new E-Max Release Technology, a proprietary coating chemistry for use on a wide variety of nutrient components that are incorporated into controlled-release fertilizer products. According to Chris Buchheit, marketing manager for Everris’ ornamental horticulture products, E-Max will help Osmocote and the company’s other existing brands deliver even better performance and value. “This coating will aid in the development of products that both complement and enhance our Osmocote portfolio and other fertilizer lines. It will increase Everris’ flexibility to create customized nutrition programs designed for horticulture growers,” Buchheit says. E-Max Release Technology is a durable, cutting-edge, reacted polymer coating for use on a variety of essential macro- and micronutrients. Nutrients coated with E-Max Technology are produced to the same performance standards as Osmocote. It will allow for continued expansion of the Everris portfolio, the ability to further enhance nutritional values and an efficient use of a grower’s […]

Read More