Fertilizing Containers

Fertilizing Containers

After water management, fertilization is the next most common problem with keeping large containerized plants alive through the summer. Most consumers do not fertilize their plants, or if they do, they don’t apply a sufficient amount to maintain the plants at good quality. In this article, we give specific recommendations about fertilizing of 10-inch baskets. For larger size pots and baskets, use these recommendations as a starting point for suggesting fertilizer rates.

How much fertilizer does a 10-inch basket need? Assuming you start with a growing medium that contains preplant fertilizers, an additional 1.5 to 2 grams of nitrogen from a balanced fertilizer is sufficient to produce a 10-inch basket in 12 weeks with no leaching. That is equivalent to the application of 7 to 10 quarts of fertilizer with a concentration of about 200 ppm N.

If you leach, you will need to use more fertilizer. Researchers at Michigan State University found that leaching fractions as low as 25 percent can remove as much as 50 percent of the fertilizer applied to the crop. In other words, if your leaching fraction is 25 percent, you will have to either increase the concentration or the frequency of fertilizer applications in order to maintain similar nutrient levels in the media compared with growing the crop with no leaching.

After production, a minimum of 5 to 6 grams of nitrogen from a balanced fertilizer is required to maintain growth and flowering of plants in hanging baskets for about 20 weeks outside. This amount of fertilizer corresponds to 2 quarts of fertilizer applied at 300 ppm N every two weeks with some leaching. Assuming that 1 level teaspoon of 20-20-20 fertilizer (a common consumer fertilizer) weighs about 6 grams, 1 teaspoon dissolved in 1 gallon of water will supply about 300 ppm N. Since most media in a 10-inch basket will absorb about 64 fl.oz. of water at each irrigation, it is sufficient to apply the fertilizer as a normal irrigation once every two weeks.

We were able to grow and maintain commercially acceptable plants using the above mentioned fertilizer program with several different species used in hanging basket production, including geraniums, ivy geraniums, fuchsia, impatiens, New Guinea impatiens and Non-Stop begonia.

It is often stated that some plants (like geranium) have a high nutrient requirement, while other plants (like New Guinea impatiens) have a low nutrient requirement. We concluded that none of the plant species tested required higher levels of fertilizer. Instead, plants that are listed as having a high nutrient requirement can tolerate higher levels of fertilizer salts in the root media without a reduction in growth. 

Understanding Slow-Release Fertilizer

Another way to supply nutrients to plants is with slow-release fertilizer. As its name implies, slow-release fertilizer is not available to the plant all at once, but rather the nutrients are released slowly to the plant over time. While there are a number of technologies for making fertilizer slow release, the most precise materials use plastic or resin to coat prills of fertilizer salts.

Unlike water-soluble fertilizers where you can measure the exact concentration for each application, the amount of nutrients released by the plastic- or resin-coated fertilizer depends on soil conditions. Once the medium has been moistened and the prill has absorbed water, soil temperature is the only factor that affects the long-term release of nutrients.

Depending on the product, the ideal release temperature can vary from 68ËšF to 80ËšF. For example, one type of resin-coated fertilizer has an ideal release temperature of 70ËšF. For a fertilizer with a 90-day release rate, 90 percent of the nitrogen fertilizer contained in the prills will be released over 90 days if the temperature of the medium is maintained at an average of 70ËšF. The higher the average soil temperature above the ideal release temperature, the faster the salts are released and the shorter the release duration. In contrast, lowering the average soil temperature below the ideal release temperature will slow the salt release and increase the release duration. 

Figure 1. Regular applications of water-soluble fertilizer (left) can maintain the quality of impatiens hanging baskets.

The liquid fertilizer treatment (left picture) received 2 liters of a fertilizer solution (20-10-20 at 300 ppm N) once every two weeks for the 57 days the baskets were outside, whereas the no fertilizer treatment (right) received only clear water.

Consumer Use

It may be unrealistic to educate all our customers to become expert in fertilization and watering. Assuming that you want to supply all the nutrients to the plant for the consumer with the slow-release fertilizer, then the rates should be equal to the amount calculated for water-soluble fertilizer, i.e. 1.5 to 2 grams of nitrogen applied during production (about three months) and 5 to 6 grams of nitrogen applied after production (three to four months).

There are two methods for applying slow-release fertilizer to a crop. The first is to incorporate the fertilizer into the root medium prior to planting. If you base your incorporation rate on the values given above for water-soluble fertilizer, then you need to add enough slow-release fertilizer to supply 6 to 8 grams of nitrogen fertilizer to each 10-inch basket over seven to eight months.

Always read fertilizer labels and do not apply more than the recommended rate. To calculate grams of nitrogen, you need to know the percentage of nitrogen contained in the slow-release fertilizer and the number of baskets that are filled per cubic yard of media. For example, to get an incorporation rate of 7 grams of nitrogen per 10-inch basket using a 17 percent nitrogen fertilizer and assuming a filling rate of 160 baskets per cubic yard of media, then you need to add about 14.5 pounds of fertilizer per cubic yard. If you used a fertilizer containing 13 percent nitrogen, then the incorporation rate would be higher, about 19 pounds per cubic yard (See Calculating Incorporation Rates). If you are using a fertilizer with a release duration of less than seven months, then the incorporation rate needs to be reduced accordingly. If the release duration is less than four months, then there is little benefit to the consumer.

The biggest problem with high incorporation rates is the potential for salt buildup in the root medium during production, especially in salt-sensitive crops, when you apply the high rate on the fertilizer label. Many greenhouses grow multiple levels of crops in the same greenhouse, so leaching a basket crop to remove high fertilizer salts may not be an option. If you choose to use these high rates of fertilizer, make sure the crop can be heavily leached if salt levels in the media reach damaging levels. Decreasing the amount of fertilizer incorporated into the medium at planting will reduce the risk of salt buildup during production, but there may not be enough fertilizer to keep the plant at its highest quality through the summer.

As with any fertility program, when using slow-release fertilizer, you need to soil test on a regular basis so an informed decision can be made whether to leach, apply additional amounts of fertilizer or apply irrigation water during production of the basket crop.

The second method of applying slow-release fertilizer is for the wholesale grower or retailer to apply the material to the root media surface (top-dress) just prior to sale. The advantage of this method is that it does not affect the nutrition management of the crop during production and a shorter-term release material can be used. The disadvantage is that it can be difficult to find the time or the people required to top dress baskets or pots during a busy shipping season and fertilizer prills sitting against the stem can damage the plant.

With top dressing, 5 to 6 grams of nitrogen should be applied if you want the plant to look similar to using water-soluble fertilizers through the summer. One tablespoon of a slow-release fertilizer weighs about 18 grams. If the fertilizer contains nitrogen at 17 percent, then 18 grams will supply about 3 grams of nitrogen (2 tablespoons would supply 6 grams). If the material contained 13 percent nitrogen, then 1 tablespoon will supply about 2.3 grams of nitrogen and 2 tablespoons will supply about 4.6 grams of nitrogen.

Better consumer education about fertilization and the use of lower rates of slow-release fertilizer by the grower may give customers their best success. Next month, we will turn our focus to nutrient tolerances of different plant species in baskets. 

Leave a Reply

More From Fertilization...

March 26, 2015

10 Greenhouse Products For First-Rate Growing Environments

From coverings to fork-lifts, greenhouse suppliers offer a variety of products to make growing easier. Check out the slideshow to learn more about these, plus several other products that can offer you value, versatility and durability.

Read More
Rose rosette on Knockout rose, April 2012. Photo credit: Alan Windham, University of Tennessee

March 25, 2015

$58 Million In APHIS Farm Bill Funding Will Support Horticulture Priorities

Nearly $58 million as been allocated by the USDA's Animal and Plant Health Inspection Service (APHIS) to support the industry's Plant Pest and Disease Management and Disaster Prevention Program, under Farm Bill Section 10007. The program will support mitigation efforts for specialty crops, including providing research and other funding to address plant pest and disease priorities for the specialty crop industry, including floriculture and nursery crops.

Read More
AFE scholarship_Ryan Dickson

March 25, 2015

AFE Educational Grant And Scholarship Application Deadlines Approaching

Apply now for American Floral Endowment (AFE) scholarships or educational grants. Applications can be found online. For educational grants for 2015-2016, applications must be submitted no later than June 1. Scholarship applications are due May 1. AFE will award $40,000 in scholarships for 2015.

Read More
Latest Stories

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

February 4, 2013

BioSafe Systems And Daniels Plant Food Company Will Par…

BioSafe Systems has entered into a strategic partnership with Daniels Plant Food Company, a wholly owned subsidiary of Ball Horticulture Inc. BioSafe and Daniels have worked closely together for the past two years and will now look to further develop liquid plant food serving both the conventional and organic markets. In conjunction, BioSafe Systems will be introducing its own branded line of plant food products focusing on turf, landscape and agricultural markets. “Liquid plant food is a natural progression for our company” says Rob Larose, CEO of BioSafe Systems. “It fits perfectly into our current line of green and sustainable products, and we are excited about partnering with Daniels.” Daniels manufactures and markets both conventional and organic liquid fertilizers, using botanical extracts to provide high-value nutrition to plants. BioSafe Systems develops and markets effective and sustainable products to a wide variety of industries, including fruit and vegetable production, turf and […]

Read More