Extension News: Turf and Lawn Care Archives

Spring is finally here. The days are longer and warmer, daffodils are popping up, and the mulch volcanoes are erupting.

The mulch volcanoes? You know, those piles of bark mulch mounded up beneath many landscape trees. I don't know where or why this practice started, but too much mulch under a tree or shrub actually does more harm than good, and is a waste of mulch and money.

Mulch serves several purposes besides dressing up your landscape. It helps retain soil moisture, important because most "feeder" roots (the roots that obtain water, air and nutrients for the tree) grow in the top 12 inches of the soil.

Mulch that's deeper than three inches can smother feeder roots and compromise the tree's health. Roots may actually grow up through a too-thick mulch past the base of the tree and encircle the trunk, a condition called girdling. As the tree grows, these roots could choke the tree and cause a slow death.

Mulch should never touch the trunk of the tree. Because it holds moisture, mulch will keep the trunk damp, encouraging bark rot and disease. Also, insects and rodents may find homes in the mulch volcano and feed on the bark of the tree.

Spread the mulch in a uniform layer two to three inches deep and out at least to the drip line (the area beneath the outermost branch tips of a tree). You want the natural flare at the base of the trunk, where it meets the ground, to be exposed. You can renew mulch each year by adding a little to the surface; there's no need to remove old mulch, but don't allow it to become deeper than four inches.

Because mulch helps prevent roots from drying out, especially when newly planted, use a quality, natural mulch. Untreated plant-based mulches are best, since they help improve the soil as they decompose. These include wood chips, bark mulch, straw, leaves, and pine needles. Avoid wood-chip mulches made from construction materials, pressure-treated lumber and old telephone poles, as these might contain harmful chemicals.

Mulch can also prevent weeds from growing around the base of the tree. Particularly when the tree is growing in a small or confined area, unwanted plants (or even flowers) may compete with the tree or nutrients and water.

Finally, mulch provides a "safe zone" between your lawn and the tree. This makes lawn mowing easier, and protects the bark from mower or trimmer damage.

If you'd like to remove the mulch volcano from your tree, do it gradually over a few months. The trunk has been kept shaded and damp from the mulch, and sudden exposure to the sun could cause it to crack. If the feeder roots have grown up through the mulch, they could dry out and lose their ability to absorb water. Remove the mulch a little at a time, remembering to water the roots thoroughly for 20 minutes each time.

You may lose some roots to exposure during this process, but in the end your tree will benefit from having deeper roots and a healthier growing environment.

By Melinda Wright, Cooperative Extension Master Gardener and Tree Steward

Photo: the Plant & Pest Diagnostic Laboratory at Purdue University Used with permission.

Lift your spirits and welcome spring with a visit to the UNH Greenhouse Open House, Friday, March 28 and Saturday, March 29 at the UNH campus in Durham.

The greenhouses will be open from 9 a.m. until 4 p.m. both days, and there's no admission charge. You'll find plenty to do and see.

• Take a guided tour.
• See UNH research projects and a breathtaking array of plants.
• Bring your gardening questions to an Ask-the-Experts session.
• Bring your sick houseplants in for diagnosis.
• Shop for plants and flowers.
• Join a question-and-answer session on carnivorous plants.
• Attend talks by UNH faculty on topics such as eco-friendly insect control on home lawns, new and different vegetables for the home garden, shoreland landscaping, and more.
• Have lunch in the Greenhouse Cafe.

The UNH greenhouses are located off Main Street in the west end of Durham. For more information about the Greenhouse Open House, call 862-3200 or view the brochure.

The calls started coming into the Family, Home & Garden Education Center in mid-May: Help, all my plants are dying! My landscaper spread mulch around them yesterday and today they are scorched, wilted, and some are losing leaves. Besides that, my lawn is yellowing alongside the mulched bed. What can I do?

Known as sour mulch, this problem occasionally shows up when hardwood mulch has been stockpiled in very large piles. High moisture and lack of oxygen towards the center and bottoms of these piles leads to anaerobic fermentation, producing by-products such as alcohol, ammonia, and organic acids that can harm plants. Storing mulch in long, low rows no more than 10 feet high and turning it frequently to expose it to oxygen will keep it from souring.

Once sour mulch is spread, plants show symptoms within a day. Sometimes they recover and other times they die. A wide range of plants, from herbaceous perennials and annuals to newly planted trees and shrubs, can be affected.

Often you can detect sour mulch by its rotten-egg, vinegary, or ammonia-like smell, although these odors dissipate quickly once spread out. It may also feel hot to the touch. The pH is very low, ranging from 2.2 to 3.5, a good diagnostic test if you suspect you have sour mulch.

Damage is quick but not long-lasting. The harmful compounds in the mulch will volatilize and/or leach out fairly quickly once the mulch is spread in a shallow layer. Landscapers who suspect they have piles of sour mulch should check the pH and, if in doubt, spread the mulch and turn it to provide aeration. Apply lots of water to leach out the toxins and apply an ample amount of lime to bring the pH back up. After a few weeks, the mulch should be safe to use.

Homeowners shouldn't buy, spread or allow application of mulch with off-odors or mulch that's hot to the touch.

Interestingly, the sour mulch occurrences this year were limited to black mulch. Of all the calls received by Cooperative Extension or the N.H. Department of Agriculture, Markets & Food, no one complained about problems with other colored or natural mulches. We were not able to trace the black mulch back to a common source, however.

by Cathy Neal, UNH Cooperative Extension nursery and landscape specialist

For more information:
Beware of Toxic Mulch
Beware of Sour Mulch
Sour Mulch

A manual for N.H. Landowners and Landscapers

No matter where you live in New Hampshire, the actions you take in your landscape can have far-reaching effects on water quality. Why? Because we all live in a watershed, an area of land that drains into a surface water body such as a lake, river, wetland or coastal estuary.

Landscaping at the Water's Edge: An Ecological Approach, a new book from UNH Cooperative Extension, explains how landscaping choices affect ground water and demonstrates how, with simple observations, ecologically-based design, and low-impact maintenance practices, you can protect--even improve--the quality of our water resources.

"Every citizen should be concerned with the impact of his or her own actions on the environment," says Extension landscape specialist Cathy Neal, one of the book's authors. "The balance of nature is easily disrupted by humans, with far-reaching impacts on water quality, soil health and stability, animal and human health, and the living ecosystems around us."

"This book will help you understand the basics of how watersheds and shoreland ecosystems function so you can use the strategies and techniques presented to help prevent soil erosion, nutrient and pesticide runoff, exotic plant invasions, and other detrimental processes associated with developed landscapes," Neal says. "Applying the principles of ecological landscaping will support wildlife and plant diversity and maintain or even improve water quality in our lakes, streams, rivers, bays and estuaries."

In addition to Neal, the book's authors include nine other UNH Cooperative Extension educators with expertise in horticulture, soils, water resources, entomology, turf grass and landscape maintenance. These educators partnered with an ecological landscape designer and consulted with state regulatory agencies to provide the most current information to help landscapers and property owners make good decisions about landscape inventory, design and maintenance practices that will protect water quality in our lakes, ponds, rivers and estuaries.

Illustrated with full-color photographs, paintings and drawings that provide clear examples of the concepts presented, Landscaping at the Water's Edge: An Ecological Approach also contains appendices that include relevant information about state regulations, recommended plant lists and other resources.

Order your copy online.

Extension launches interactive turf-management Web page

Interested in getting a greener, healthier lawn and having fun learning how?

UNH Cooperative Extension educator Sadie Puglisi and Web specialist Faye Cragin have teamed up to produce Integrated Pest Management for Turfgrass, an interactive Web site about caring for grass in home lawns, as well as in municipal and commercial landscapes such as athletic fields, cemeteries, golf courses and office parks.

"I wanted to create an alternative to flat fact sheets for teaching people about managing pests in lawns," says Puglisi. "I wanted them to go beyond simply buying and applying lawn-care products--to understand why they need a product and how the product is going to work. Armed with that understanding, they can move on to ask another question: Do I really need this or that product?"

The pages offer information on the basics of integrated pest management, how grass grows, identifying and managing turf diseases, scouting for grubs, an herbicide glossary, and interactive decision tools about herbicide use. Quizzes at the end of each section will test your knowledge.

"The information on the site is easy to follow and helpful to anyone who wants to know how to have healthy grass," says Puglisi. "Come have a look for yourself."