Improving Rewetting

Improving Rewetting

 

Once mixed containers or baskets are sold to a customer, their subsequent watering greatly affects the “use by” date of the plant product and overall consumer satisfaction. How easily the medium rewets is a key to your consumer’s success. It may be unrealistic to educate all our customers to become expert irrigators. If water runs out through channels or flows off the media surface because of poor rewetting, customers are unlikely to water thoroughly. The choice of media components or the use of a wetting agent can improve rewetting. 

Understanding Rewetting Characteristics

Rewetting ability refers to how rapidly a root medium absorbs water, and thus reaches its potential for maximum available water-holding capacity, with minimal leaching. Unfortunately, many of the components used to make container media do not absorb water easily. For example, organic materials such as peat or bark tend to be hydrophobic and may be difficult to rewet if allowed to become too dry.

Researchers have shown that when the water content (by volume) of pine bark was allowed to decrease below 35 percent, little of the water applied in a single irrigation was retained. As moisture levels increased to 50 percent, the bark became progressively more efficient at retaining the applied water.

The state of decomposition of the peat or bark may also affect the ability to rewet after drying. Older, more degraded peats contain relatively high amounts of humic acid. Humic acid plays an important role in the lime requirement and the cation exchange capacity of peat. However, if degraded peats are allowed to become excessively dry, the humic acid may form hard granules that have lost their initial capacity to absorb water, making them more difficult to rewet.

Amendments such as vermiculite, rockwool, sand or calcined clay can be added to a root medium to increase rewetting. These materials improve rewetting ability because they absorb or distribute water independent of their moisture content prior to water being applied. Water can therefore be absorbed and distributed by the root medium even when the peat or bark is dry. When using amendments like vermiculite or calcined clay to help with rewetting, it is important to add them into the medium at a high enough percentage to influence water absorption (often 30 percent or more by volume). 

Wetting Agents

Improving Water Relations In Large Containerized Plants

In the last three articles, we have outlined various methods for extending the time between watering. Here we give our opinion on benefits and costs (Table 1).

Maximize rewetting. The reapplication of a wetting agent before you ship baskets improves their potential to rapidly and easily absorb water without having to change your media. At about $0.015 to $0.03/10-inch basket (see assumptions in Table 1), this is also low cost.

Increase available water-holding capacity. This requires that you change your medium. In general, you want to switch from components that are solid (polystyrene or perlite) to ones that absorb water (vermiculite or rockwool). Another way is to increase the percentage of peat and decrease the percentage of other components, which may decrease or increase cost. Media with high available water-holding capacity are unfortunately easier to overwater, especially just after planting. Changing the components or peat percentages can also change lime rates.

Change water release. Changing the water release characteristics of your media is a lower priority because you will get a greater benefit at a similar or lower price by increasing available water-holding capacity than by changing water release. Having said that, adding a gel or calcined clay to a medium will reduce the maintenance required to keep plants alive through the summer, and therefore should be considered.

Much of the research to improve rewetting ability of peat has evaluated wetting agents (also termed surfactants). Many surfactants exist but many are phytotoxic to plants. Wetting agents used in horticulture are nonionic materials that bind to the surface of the root media particle and decrease the surface tension of the water, thus increasing the penetration of water into the root media. Because of the hydrophobic nature of peat and bark, wetting agents are commonly added to root media at mixing to aid in rewetting. 

The useful life of a wetting agent depends on factors such as media storage duration and temperature before planting, media components, watering practices and wetting agent rate and type. For example, impatiens were grown in 10-inch baskets using 18 commercial media, each containing a wetting agent added at mixing. After six months, AquaGro wetting agent was reapplied as a drench to half the baskets from each media.

The reapplication of the wetting agent had no effect on available water-holding capacity in the media containing long-fibered grower-grade peat. However, in media containing more degraded peats, the reapplication of a wetting agent increased available water-holding capacity by as much as 50 percent compared to the same media without the wetting agent drench.

Reapplication of a wetting agent is necessary if you notice that considerable leaching is needed before the medium is moist through the entire profile. About 10 minutes after an irrigation, pull off the pot and check whether the entire root zone is moist. Patchy drying of media can sometimes indicate poor rewetting. You can also measure rewetting directly.

Rewetting ability, available water-holding capacity and water release characteristics determine whether your customer is able to keep a plant alive during the summer, and whether you will have a repeat sale next year. Next month, we will turn our focus to fertilization for success with baskets.

Leave a Reply

One comment on “Improving Rewetting

More From ...
Gaillardia x grandiflora 'Arizona Apricot'

February 25, 2015

National Garden Bureau Designates 2015 As Year Of The Gaillardia

Gaillardia, also known as the blanket flower, is a member of the sunflower family (Asteraceae) and a long-blooming pollinator plant. It is fitting that the National Garden Bureau has specified 2015 as The Year of the Gaillardia.

Read More
IPPS Sharing Plant Production Knowledge Globally Logo

February 25, 2015

International Plant Propagators Western Region Sets Annual Meeting Date

The annual meet for the International Plant Propagators' Society (IPPS) Western Region has been set for this September. It will take place September 23 to 26 in Modesto, Calif., and will include learning sessions, tours to local nurseries, a research poster display and poster presentations, various networking opportunities and an awards banquet to close the event.

Read More
Evolvulus Blue My Mind

February 24, 2015

Blue Ribbon Bloomers For Greenhouse Production

Grow what consumers want! Surveys show that blue is one of the top preferred colors of today’s consumers. Here are twelve top recommended blue-flowering Proven Winners annuals and perennials to suit your spring production cycle.

Read More
Latest Stories
Gaillardia x grandiflora 'Arizona Apricot'

February 25, 2015

National Garden Bureau Designates 2015 As Year Of The G…

Gaillardia, also known as the blanket flower, is a member of the sunflower family (Asteraceae) and a long-blooming pollinator plant. It is fitting that the National Garden Bureau has specified 2015 as The Year of the Gaillardia.

Read More
IPPS Sharing Plant Production Knowledge Globally Logo

February 25, 2015

International Plant Propagators Western Region Sets Ann…

The annual meet for the International Plant Propagators' Society (IPPS) Western Region has been set for this September. It will take place September 23 to 26 in Modesto, Calif., and will include learning sessions, tours to local nurseries, a research poster display and poster presentations, various networking opportunities and an awards banquet to close the event.

Read More
Evolvulus Blue My Mind

February 24, 2015

Blue Ribbon Bloomers For Greenhouse Production

Grow what consumers want! Surveys show that blue is one of the top preferred colors of today’s consumers. Here are twelve top recommended blue-flowering Proven Winners annuals and perennials to suit your spring production cycle.

Read More
myers industries Lawn and Garden Logo

February 24, 2015

Myers Industries, Inc. Lawn And Garden Business Sold, N…

The management of Myers Lawn and Garden Group, along with Wingate Partners V, L.P. have recently acquired the Myers Industries, Inc. Lawn and Garden business. The new company is named The HC Companies, and will continue as a North American leading provider of horticulture containers supplying the greenhouse, nursery and retail markets.

Read More
Outfitting Your Greenhouse

February 24, 2015

Save Energy With The Right Greenhouse Glazing

The glazing you choose can make a big difference in your energy bill and the uniformity of your crops.

Read More
Rough Brothers aeroponic greenhouse project

February 24, 2015

Rough Brothers Takes A Hands-On Approach To Several Pro…

Two projects Rough Brothers worked on for Altman plants in Giddings, Texas, and Scissortail Farms in Tulsa County, Okla., show that pre-planning on the grower's part opens the way for a smooth-running expansion project.

Read More
Michigan State University Extension

February 24, 2015

Ethylene From Defective Greenhouse Heaters Damages Crop…

Malfunctioning greenhouse heaters can lead to crop damage from ethylene and carbon monoxide induced illness for workers. Michigan State University's Extension educators Tom Dudek and Randy Beaudry teach you how to recognize the symptoms and check greenhouse heaters to avoid the concern.

Read More
Stuppy Greenhouse Manufacturing's Rainbow Super Structure

February 23, 2015

Stuppy Greenhouse Manufacturing Says Every Customer’s G…

Well-suited greenhouses that function efficiently for customers arise from involving them in the design process from start to finish. Stuppy Greenhouse Manufacturing put this philosophy on a greenhouse design for a wholesale grower looking to expand his annuals operation. The grower's needs were simple, yet daunting: design a greenhouse that delivers the perfect growing environment, but keep maintenance and operating costs low.

Read More
Havest Automation Robot

February 18, 2015

Robots Grab Hold Of Growers’ Material Handling Needs

Harvest Automation’s HV-100 robots automate one of the hardest, most labor-intensive jobs at growing operations – plant spacing. With more technology coming, investing in robots could become even more realistic for growers of all sizes.

Read More

February 18, 2015

Range Of Nursery Inspections To Protect Patented Plants…

Plant patents are under protection, and breeders are fighting for their rights to keep growers from illegally propagating protected varieties. It's something you don't want to take a chance on, because the risk is far higher than the reward. More than 300 inspections were carried out last year from New York to British Columbia and from Ontario to Florida to protect plant patents, Plant Breeders’ Rights (PBR) and branded programs.

Read More

February 18, 2015

California Spring Trials Sneak Peek: New Annuals For 20…

If you're like us and you can't wait until the 2015 California Spring Trials to see some of the new genetics that will be hitting the market in 2016, never fear. We contacted the breeders who will be displaying their new varieties in California in April, and they gave us a sneak peek. Check out our slideshow to see some of the new annuals making their debut to the trade this spring.

Read More
Athena Brazil Salvia 'Brazilian Purple'

February 18, 2015

ForemostCo And Athena Brazil Unite To Supply Unrooted P…

ForemostCo, Inc. and Athena Brazil have forged a working relationship to support each other in the unrooted perennial cuttings market for North America. The partnership, geared toward accommodating increasing demand for unrooted perennial cuttings in North America, adds diversity to a recently consolidated market.

Read More

February 17, 2015

Poinsettias Had Their Best Year In Many In 2014

Poinsettia growers report a strong year in 2014, thanks to a few conditions. Growers were encouraged by high plant quality, enthusiastic shoppers and a stronger, less saturated market for poinsettias throughout the selling season. Seasonal cold at just the right time put consumers in a festive mood to buy early and often, and with no big snowstorms to hold up shipments and a reduction of supply available in the market, the season was strong from start to finish.

Read More

February 17, 2015

A New Look At Biological Control: Can Plants Affect The…

The success of a biological control program depends on a number of factors including quality of natural enemies, timing of release, release rates and environmental conditions. However, what is typically not taken into consideration is how plants can affect the performance of natural enemies, including attack rate and searching ability. Biological control agents work hard to protect plants, but plants have ways to help themselves, too.

Read More
american-hort-logo

February 17, 2015

AmericanHort Announces New Board Members

AmericanHort recently announced the election of new officers and members to the board of directors. Each will assume their positions on the board during Cultivate’15, July 11 to 14 in Columbus, Ohio.

Read More
All American Selections

February 17, 2015

All-America Selections Elects New Officers, Names New J…

While meeting during the Flower and Vegetable Seed Conference in Tampa, Fla., hosted by the American Seed Trade Association, All-America Selections elected new officers for a two-year term. Read on to learn about the new officers, as well as all of the new judges that were added in 2014.

Read More
Geranium x cantabrigiense 'Biokovo'

February 17, 2015

Geranium Hybrid ‘Biokovo’ Dubbed 2015 Peren…

Geranium xcantabrigiense ‘Biokovo,' a naturally occurring hybrid of G. dalmaticum and G. macrorrhizum, is the Perennial Plant Association's top pick for 2015 Perennial of the Year. Learn why this tough, landscape geranium took home the prize.

Read More

February 12, 2015

GROW Perspective: What Is It You Do Again?

The industry is very good at talking about what we do and how we do it, but has almost completely lost touch with talking about why this work is important. As an industry, we need to promote our professions as vital to healthier living.

Read More