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

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

Latest Stories
cannabis-planted-in-a-greenhouse

September 29, 2016

The 10 Most Common Misconceptions About Greenhouse Cann…

In an emerging market such as cannabis, there can be a lot of bad information out there. One greenhouse supplier points out some common myths.

Read More

September 28, 2016

Pennsylvania Greenhouse Grower Applying For Cannabis Li…

Allen Wagner of Wagner’s Greenhouse in Grandview, PA, hopes to become one of 25 applicants — among as many as 150 — chosen for a grower-processor license.

Read More
finneran bee on snakeroot

September 28, 2016

Which Annuals And Perennials Are Good For Pollinators?

If you are a grower looking for information on producing plants that are safe for pollinators, or which plant types can be marketed as good food sources for bees, the new publication “Protecting and Enhancing Pollinators in Urban Landscapes” provides a good resource.

Read More
The-Capitol

September 28, 2016

How The November Election Might Affect The Legalization…

National polls indicate Americans are largely divided on the topic, while this year’s presidential candidates generally feel it’s a state issue.

Read More
tomato spotted wilt virus angular-necrosis-of-leaves-and-plant-stunting

September 28, 2016

Tips For Managing Tomato Spotted Wilt Virus In Mums

According to a report from Michigan State University, symptoms of tomato spotted wilt virus on chrysanthemum include yellow blotching and rings, necrotic lesions, and stem collapse.

Read More
cannabis-crop-protection

September 27, 2016

Washington State Outlines Pesticide Criteria For Cannab…

The state has also compiled a searchable list of pesticides that fit the criteria for use on marijuana.

Read More
Vogel Alcove NGB Therapeutic Grant Winner

September 27, 2016

National Garden Bureau Announces Horticulture Therapy G…

The NGB’s annual grant program, Growing for Futures, recently selected three therapeutic gardens that will receive grants totaling $5,000.

Read More
phlox-fashionably-early-flamingo-walters-gardens

September 27, 2016

Walters Gardens Partnering With Darwin Colombia On Unro…

Beginning in spring 2017, Darwin Colombia will offer unrooted cuttings of more than 40 varieties of Walters Gardens’ new genetics, including many popular genera such as Agastache, Monarda, Nepeta, and Phlox.

Read More
totalgrow-night-and-day-management-boom-lighting-venntis-feature

September 27, 2016

Check Out The Latest In Lighting Technology For Greenho…

Manufacturers are developing several innovative lighting systems that can help growers save on energy efficiency, while improving plant quality. Here’s a look at some of their newest offerings.

Read More
cuttings-facility

September 27, 2016

How Global Suppliers Of Unrooted Cuttings Are Working T…

The world’s top vegetative producers discuss how they continue to evolve to overcome challenges and embrace opportunities to help growers and the varieties supply chain.

Read More
Streptocarpus Ladyslippers Grape Ice (Green Fuse Botanicals)

September 27, 2016

9 New Blooming Potted Plants To Jazz Up The Home And Ga…

Blooming potted plants are the ideal gift for anyone, from a homesick college student to a spouse in need of some cheering up. Check out nine these new introductions hitting the retail market in 2017.

Read More

September 27, 2016

Kitchen Counter Gardening Leads Garden Media Group̵…

This year's list includes several items around healthy living and eating, from gardening indoors year-round, to "forest bathing."

Read More
bruce-butterfield-and-ngs-image

September 27, 2016

Bruce Butterfield, National Garden Survey Researcher, D…

The man who headed up the National Gardening Survey for the past 35 years, Bruce Butterfield, has died. He was 67 years old. Butterfield’s work with the National Gardening Survey gave the green industry a reliable tool to understand consumer gardening practices and spending. Bruce Butterfield started his career as the Market Research Director at the National Gardening Association in 1978 and continued that same work until his death on September 5 as the Research Director at GardenResearch.com. “These many years of experience doing market research about gardeners and gardening trends gives him a unique understanding of who gardeners are, what they need and want, why they buy the products they do, where they shop, how gardening trends have changed in the past, and where they are headed in the future,” his bio on GardenResearch.com reads.       Butterfield was also behind What Gardeners’ Think and the Environmental Lawn […]

Read More

September 26, 2016

How Even An Overworked Plant Retailer Can Predict Consu…

Years ago, I read an article about Pottery Barn and the women who were making it a success. It was eye-opening to realize that a glossy, national chain like Pottery Barn used to buy products in a similar way garden retailers do. There was one section of that article that really caught my imagination. It was the profile of Celia Tejada, the woman who moved Pottery Barn from buying products from outside vendors to designing their own products. When Tejada joined Pottery Barn, she instructed her entire staff to begin keeping an eye out for things they liked, no matter how minor. So if they were at a restaurant with friends, or walking along a street and something caught their eye, they were to either buy it or photograph it and place it in a room set aside for these kinds of inspiration. When it came time to select themes for the […]

Read More
urban-outfitters-logo-feature

September 26, 2016

Terrain’s Parent Company Breaks Impass For Waterl…

There’s been a development in the stalled plans for a new Terrain garden store from Urban Outfitters on the former Waterloo Gardens location. In a letter to Easton Township, PA, officials, Urban Outfitters’ Chief Development Officer J. David Ziel says the company is removing a key element that had met strong resistance from the community around Devon Yards, its term for the development plan on the former Waterloo Gardens site. Devon Yards will no longer include a four-story apartment building in its “lifestyle center” project, Ziel wrote. But it will still include its third Terrain store, a large format Anthropologie, and several eateries. The planned apartment building had created friction with local residents, Mainline Media News reported back in April. While residents welcomed the retail aspects of the plan, they felt a large apartment building would change the character of the community. The developer who will work on the project, […]

Read More
Orius_June 2015

September 25, 2016

Peace Tree Farm Hosting Biocontrols Event In October

“Advanced Greenhouse Biocontrols for Ornamental and Vegetable Producers” will feature advice from biocontrol authorities Lloyd Traven and Suzanne Wainwright-Evans.

Read More
sbi-software-triumph

September 25, 2016

Greenhouse Software Suppliers Offering A Range Of New S…

Want to know what some of the leading software suppliers are doing to address the ever-evolving needs of their greenhouse customers? Here’s a brief update.

Read More
cannabis-lighting

September 24, 2016

4 Tips On Picking The Best Lighting System For Cannabis…

From energy use to maintenance, here are some suggestions from one expert on how to ID the best lighting system for your greenhouse.

Read More
[gravityform id="35" title="false" description="false"]