Should You Use Cypress Mulch?

Gardeners love cypress mulch for a number of reasons. It's organic and lays flat in a thick mat that keeps weeds from growing up or unwanted seeds from tunneling down into the soil underneath. It stays in place through wind and rain and typically will last several seasons before it starts to decompose. And when it finally breaks down, it adds nutrients to the soil. According to the home guides section of SFGate, it won't change the soil pH when it goes.

What's Wrong With That?

Plenty, says a national gardening group, some academics and scientists, and a host of environmentalists. Among the many items on their list of concerns, several stand out. One is that cypress trees are logged from ecologically sensitive wetland environments. Another is that many other natural options work just as well, if not better, than cypress.

Welcome to one of the hot-button issues in American gardening: the controversy about harvesting cypress trees and using the mulch in home gardens.

The Case for Cypress Mulch

This is a familiar topic to the Mulch and Soil Council (MSC), a national nonprofit trade association for producers of horticultural mulches, consumer soils, and commercial growing media. It certifies mulches, including cypress mulch and cypress mulch blends, to ensure they conform to industry standards.

In 2010, MSC executive director Robert LaGasse attended a conference in Atlanta that took place near the end of an Environmental Protection Agency (EPA) project focused on cypress wetlands. The project examined whether increasing demands for cypress products were affecting naturally occurring cypress wetlands. According to the EPA, the intent was to conduct an extremely thorough analysis in one state (Georgia) within the Southeastern Coastal Plain to better understand the extent and causes of cypress wetland losses, where things stood with the science of restoration and what were best practices for silviculture (tree farming) in cypress communities.

In addition to the EPA, other stakeholders at the conference included the Southern Environmental Law Center (SELC), several academics (including a professor and researcher from Clemson University who specializes in cypress, William H. Conner), the Georgia Forestry Commission, and representatives of trade groups such as the Mulch and Soil Council. The meeting took place about the time that the SELC, at the request of the EPA, was producing a report from the project titled "Status of Private Cypress Wetland Forests in Georgia.” It was published in 2012.

LaGasse’s takeaway from the Atlanta meeting was that, although there were some sites in Georgia that were negatively affected, those were “highly developmental sites where the investors and builders were trying to make and expand cities and towns.” But when looking at the overall health of the forest in Georgia and the Southeast and comparing logging and tree loss to the growth of the forests, the growth “far outstripped mortalities and removals.”

His conclusion from the gathering was that “the claim that the cypress forests in Georgia were being over-logged [was] simply not accurate.” He said he left the meeting thinking that cypress logging was within reasonable sustainable parameters and until those changed there was no need for further action.

Since that conference, the supply of cypress in the mulch industry has flattened out, according to LaGasse, who based that assessment on a conversation with a major retailer. “According to their numbers, it’s flattened out for several years now. We don’t see that product line growing. The number of people who are producing it has declined. The supply has declined. There’s still some consumer demand, but that market hasn’t grown as it has with other product lines, and most of the [cypress mulch] products you’ll notice are not pure products, they are blends.” The use of hardwoods and soft woods in the lawn and garden industry far exceed the use of cypress, LaGasse said.

Trends in cypress mulch sales are hard to verify. “Unfortunately, we don't break down mulch usage by type of wood,” said Paul Cohen, research director of Garden Garden Research. A check on Market Research and a few other research aggregators did not find any sites that subdivided the mulch market into the cypress category, he added.

A Forest Inventory Assessment conducted by the U.S. Forest Service Inventory & Analysis Branch in Knoxville, Tennessee, seems to support LaGasse’s contention that cypress is not overharvested. The latest data for the entire South, covering 2009-2017, show that average annual removals of cypress equal less than 1% (0.54%) of total cypress volume. The growth of cypress trees in the South is 3.8 times that of cypress tree removals.

LaGasse sees several upsides to cypress mulch. “Mulch is probably the most successful recycling program in existence today,” he said. “Without a mulch market, the alternative is to send trimmings to landfills and to leave scrub trees that must be removed to access merchantable saw timber in the forest, where they become debris creating fuel for fires and pest infestations. We look at the creation of mulch as offering a service that provides an alternative stream of revenue to the landowner, that removes materials that should not be left in the forest and that prevents those materials from over-burdening landfills and public facilities.”

The Case Against Cypress Mulch

Bill Sapp, a senior attorney for the SELC, also attended the 2010 meeting in Atlanta and co-authored the report about cypress forests in Georgia. His recollection of the gathering was that it didn’t produce any agreements.

To understand SELC’s conclusions, it’s important to know how the organization produced the report, Sapp stressed. “We spent over a year looking at all the data we could find,” he said. “The other thing to know ... is that the scientist we hired to work on the report, Will Conner, is one of the leading scientists studying cypress in the country.” Conner is a professor in the Forestry and Environmental Conservation Department at the Baruch Institute of Coastal Ecology & Forest Science (near Georgetown, South Carolina), which is affiliated with both Clemson University and the University of South Carolina. He has studied cypress for 43 years.

“The real heart of the report, and the reason the EPA wanted us to prepare the report, was to make sure that activities such as lumbering allowed the cypress resource to be sustainable,” said Sapp. “We found that there are certain threats to cypress ecosystems.”

The report, which points out that Georgia ranks third nationally in cypress forest acreage but fifth in the loss of various species to extinction, lists those threats as:

• Regeneration: Cypress forests are rarely replanted after they are harvested.
• Hydrology modifications: Reservoirs, canals, channels, and other structures have changed how water flows across Georgia’s coastal plain.
• Development and insufficient legal protection: More people are moving to the coast, and some developers are abusing the Clean Water Act’s silviculture exemption. That exemption is for “normal” tree farming operations, which does not include draining wetlands, said Sapp. It also means that tree farmers cannot build roads over a certain width, he added.
• Conversion to pine plantations: Small depression cypress ecosystems are being converted to pine plantations. This is the habitat for pond cypress (Taxodium ascendens), one of three types or cypress that grows in the United States. It is also the type of cypress that Sapp said was the focus of the report. The other types of cypress growing in the United States are bald cypress (Taxodium distichum), which grows in river floodplains, and Montezuma cypress (Taxodium mucronatum), which grows in the Rio Grande Valley in Texas south to the highlands of southern Mexico.
• Increased harvesting and mortality: There has been an overall increase in cypress harvesting and cypress mulch production.

“We think, based on the research we’ve done, there are concrete threats to the sustainability of cypress,” Sapp said. However, he also acknowledged needing more data to gauge the extent of those threats, which he said is one of the over-arching themes of the report. To emphasize that the SELC stands by the data in the report, he noted that it includes a confidence range for the statistics used. “That’s something you don’t always see in scientific reports.”

Better Alternatives

Sapp said it’s important for home gardeners to know that the report challenges the assumption that cypress mulch is more durable and longer-lasting than other mulches. The report cites University of Florida Cooperative Extension Service research that evaluated 15 different kinds of mulches during a six-month period to compare their effectiveness. Three mulches—wood chips, pine bark, and pine straw—rated just as high as cypress. Gardeners should also be aware that when cypress mulch is used in full sunlight it can form a crust that reduces the amount of water getting to plant roots, according to the report.

One reason cypress mulch didn’t outlast other mulches has to do with the age of the trees. The report says that while the heartwood of very large, older trees contain chemicals that help preserve the wood and make it more resistant to rot, those trees are used in saw timber, not mulch. Mulch is made from younger trees that lack that heartwood. Apparently that also affects its ability to repel termites; older trees were able to do this, whereas younger-harvested one attract the pests.

The National Gardening Association (NGA) thinks the potential environmental downsides are big enough to discourage using cypress mulch. “Cypress is definitely a huge part of the ecosystem,” said Dave Whitinger, executive director of the NGA. Whitinger lives in Jacksonville Texas, a small town in the eastern part of the state near cypress wetlands.

He listed several reasons why gardeners don’t need to use cypress. One is that there are other and better kinds of mulch that can be produced in a more sustainable way from hardwoods and softwoods; free mulch is available in many communities from municipal public works departments; and sometimes factories will grind up pallets or other materials and give them away as mulch.

For example, cedar mulch has natural insect-repelling properties, as it produces an aroma that's distasteful to bugs. It's also an effective weed inhibitor when placed around shrubs, flower beds, and trees. Made from hardwood, it tends to last longer than cypress, which is made from all parts of a cypress tree. Some gardeners prefer cedar because it's less acidic than cypress.

Whitinger acknowledges that using cypress mulch isn’t going to wipe out the trees forever. “But it’s kind of like this: You can make an omelet with cardinal and bluebird eggs, but why do that when you’ve got chickens that lay perfectly good eggs? It’s not that cardinals and bluebirds are in danger of going extinct. It’s that the cypress are the cardinals and the bluebirds of the tree world. It’s worth protecting them because they are special, whereas pine trees are not special.”

How Cypress Grows

Fortunately, despite various environmental pressures, we have quite a bit of cypress left today, said Conner, the Clemson researcher. With the exception of a few small, isolated stands, cypress found in the Southeast today is the result of growth since the mid-1920s. From 1890-1925, according to Connor, “pretty much all of the cypress in the Southeast was harvested. About the same time the logging ended, there was a big drought about 1924-26, so a lot of the trees that we have now got started in that two-year time period.”

The seeds of bald cypress, the majestic tree that grows on the edges of rivers and streams and the type most people probably think about when they think of cypress, need periods of drought to take root.

“Usually it takes a two-year dry-down period,” said Conner. During that time, the seedlings must grow tall enough to keep their top leaves above the water when the floods return. “It’s got to grow a foot to two feet tall in most cases to get above that water,” Conner said. Other good times for seedlings to get started happened in the ‘60s and between 2008-2012, Conner said.

What Is the State of Cypress Today?

It’s not clear which states produce the most cypress mulch and how much comes from trees harvested specifically for mulch versus what’s produced as a lumber product. The data just isn’t readily available.

”In the early 2000s,” Conner said, “there was a big push about cypress mulch that was coming from Louisiana and parts of Georgia.” For example, the Winter 2008-2009 newsletter of the Louisiana Forest Products Development Center said that Lowe’s, Home Depot, and Walmart decided in the fall of 2007 to no longer sell cypress mulch that came from Louisiana, citing environmental concerns.

Today, Lowe’s has a sourcing moratorium that prohibits cypress mulch harvested from an area south of I-10 and I-12 in Louisiana, a place where scientists say cypress forests may be particularly vulnerable. Lowe’s sells cypress mulch products but also offers multiple alternatives, including pine nuggets, hardwood, eucalyptus, cedar, stones, pine needles, and recycled rubber, according to a spokesperson.

Home Depot has a similar policy. While it sells cypress mulch products, any cypress mulch from Louisiana eastward through the Florida panhandle must be harvested north of I-10. The company’s policy also stipulates that vendors cannot supply stores with mulch harvested from coastal cypress, said a company spokesman. That policy includes cypress growing on both the Atlantic and Gulf coasts. Home Depot gets written confirmation from each supplier stating they are compliant with the company’s cypress mulch requirements.

Each coastal state sets its own coastal boundaries, said Conner, and both bald and pond cypress can grow outside those boundaries.

Walmart did not respond to a request for their cypress mulch policy.

“Since 2012, it’s been sort of quiet,” Conner said of the cypress mulch controversy. “No one’s really mentioning it now.” Still, there are other danger signs that raise additional concerns about the health of cypress ecosystems. In some areas along the Southeastern coast, Conner said, salt water intrusion from rising sea level has killed many trees. Their standing skeletons are called ghost forests.

“In those wetland areas where cypress grows with other trees such as water tupelos, maples and ashes, those trees are even less tolerant [of salt water] than cypress. So, you end up in these coastal areas where cypress is the last thing there. And once it’s gone, it converts to marsh or open water areas such as a lake or a pond,” Conner said.

In Louisiana, the issues with cypress logging are small compared to problems caused by salinity, said David Creech, Regents Professor Emeritus at Stephen F. Austin State University in Nacogdoches, Texas. Creech is also director of the university’s gardens, which he said include the best collection of cypress genotypes anywhere in the world. “Basically, we are destroying South Louisiana with canals that have allowed salt water from the Gulf of Mexico to penetrate inward,” Creech said.

The Mississippi River naturally flowed into the Gulf “in a thousand different fingers,” Creech said. Now it’s been channeled—“shotgun[ned] into the Gulf,” said Creech—and the land where it used to flow is eroding and soaked with salt. “Some of the cypress that have died from the salt water are 20-30 years old and they still stand. They’re just dead crag heads,” Creech said.

“There’s no doubt the channelization of rivers suddenly transformed the economy. Commerce by water proved immensely profitable. However, managing rivers for commerce almost invariably leads to nearby ecosystem disturbances that are difficult to mitigate. Add in climate change predictions of rising seas, more violent storms and it's no wonder coastal lands are in trouble," Creech said.

Another cause for the decline of the majestic Southern cypress forests is one most people have never heard about: the extinction of the Carolina parakeet. It was the only parakeet native to the eastern United States and once numbered in the hundreds of thousands.

Among other things, the birds ate cypress seed. “We only know this from examination of crops by some of the early naturalists and painters like Audubon,” Creech said. “As to which species of cypress, we don’t know. But, because of its habitat in old forests along rivers, I would guess mainly bald cypress. The Carolina parakeet was found from southern New York and Wisconsin to the Gulf of Mexico. Therefore, it could have spread seed over much of the range of cypress."

Conner continued: “There were so many of them that they were considered a pest. They were hunted mainly for their pretty feathers, which were bright greens and yellows.” Their populations dropped dramatically in the 1850s and 1860s, just a few decades before the intense cypress logging that began around 1890. The last bird died in the Cincinnati Zoo in 1918. Without the parakeet to distribute seeds, bald cypress depends on the little round seed cones, which contain about 10-12 seeds each, floating on water and finding a habitable spot along the edges rivers or streams.

What Is the Future of Cypress?

Because the original stands were logged long ago, Creech says we live in what he calls “a cut-over bald cypress world. It’s all about resource management now.”

Donald Rockwood, professor emeritus in the School of Forest Resources and Conservation at the University of Florida, has co-authored a paper he expects to be published in 2018 that offers a management solution. The paper suggests transitioning from what Rockwood calls a hunter-gatherer approach to an agricultural one. That would mean growing and harvesting cypress on plantations, like pine is grown now. The paper predicts that cypress trees grown on commercial non-wetland plantations in Florida could be harvested for mulch in initial rotations as short as 10 years. It would take longer—maybe 25 years—to grow trees big enough to be harvested for timber.

Rockwood also has another management solution: eucalyptus mulch. He calls eucalyptus plantations a pet project and noted that Scott’s Landscape mulch, for example, uses eucalyptus trees from South Florida. “So, there are other equally if not better kinds of wood that can be used for landscape mulch compared to cypress,” Rockwood said.

Ingredients in Scotts’ mulch products include: pine, ash, maple, eucalyptus and even some citrus in its southern products. Scotts has not sourced cypress in its mulch products since about 2012, a spokeswoman for The Scotts Miracle Gro Company said. The decision was made in part because of the role native cypress plays in wetlands, and also because the company wanted to source raw materials as close to its facilities as possible—typically within a 100-mile radius. The company’s potting mixes, soils and mulches are mostly composed of organic waste from forestry, farming and food processing; bark, manure, rice hulls, compost, and landscaping green waste.

The future of cypress is one of the important ecological questions of our time, said Conner. “In some ways, the status of cypress looks very healthy. In other ways, when you start to look at all the impacts, you begin to wonder just how long we will have these cypress trees.”

Three things concern him: development, logging, and rising sea levels. Of these, he sees rising sea levels as probably the greatest threat. “Logging isn’t like the logging that was going on back in the early 1900s,” he said. “It’s a nice wood to work with, and so there’s always going to be some logging. But if it’s managed properly, logging can be done without much of a threat. With development, hopefully we can have some control over it. So, I think sea level rise is probably the biggest threat to cypress right now.”

How much time is left for researchers like Conner to figure out how to best preserve the mixed cypress forests and wetland ecosystems where bald cypress grows, or the areas that provide the habitat for pond cypress? Will our grandchildren still paddle kayaks or canoes along quiet, murky rivers and streams as smooth as a tabletop and marvel at the cypress trees standing as sentinels? No one knows for sure. And “that,” Conner said, “worries me sometimes when I think about it.”