Following a full day of soil science education and information exchange with consultant Eric “T” Fleisher, Swarthmore College’s Organic Lawn Care Initiative is one step closer to implementation. As I discussed in my last blog post, I am spending my summer internship helping the Grounds Department and Scott Arboretum transition the five-acre Mertz field into an organic lawn, and Monday, July 12 was a critical day in this process. T’s visit is the first pass toward a feasible and effective detailed program design.

We approached T after hearing about his work on Harvard University’s Soils Restoration Project, upon which our program is roughly based. T is the Director of Horticulture at the 37-acre Battery Park City Parks Conservancy (BPCPC) in lower Manhattan. Since 1989, he has been guiding the organization in the use of sustainable grounds management methods, based on the development of a balanced soil ecology, with an emphasis on composting, water conservation, and the use of non-toxic means of pest and disease control. BPCPC is the only public garden space in New York City to be maintained completely organically.

T presents his lecture “Managing the Environment: An Adaptive Challenge” in the Gillespie Classroom of the Wister Center. photo credit: C. Robertson

T began his Swarthmore visit with a presentation and question and answer session on his experience with organic horticultural practices. It was attended by 35 representatives of our staff, the college Sustainability Committee, the Pennsylvania Horticultural Society, local public gardens, Penn State research and extension centers, and local turf care companies. He explained to the audience that pioneering new techniques for managing environmental systems is an adaptive, rather than technical, challenge. Exploring new sustainable management practices requires philosophical and behavioral changes, moving beyond the established “quick-fix” answers that are effective in 85-90% of situations.

Applied to organic lawn care, an adaptive approach means understanding the turf as an environmental system before making any amendments. To attain this perspective, T spent the afternoon conducting a comprehensive site assessment. We gave him a tour of our compost facilities, showed him where we plan to install two solar-powered compost rotators, our compost tea brewing station, and explained what equipment and resources we own or have access to. Then, similar to what I performed last month, T used a spade to gather more soil samples. This set will be sent to a lab called Soil Foodweb, which specializes in biological content testing. Once the tests establish what microorganisms are already present in our soil and compost, T will help us further develop and modify our composting program (already 80% of the way there!), create the compost tea recipes that will best foster natural nutrient cycles in the soil, and adapt our irrigation, aerating, and mowing practices.

Revitalizing boxwoods in the North End Parks of the Rose Fitzgerald Kennedy Greenway. Top to bottom: late March, applying compost tea, early July. photo credit: T. Fleisher

T successfully uses organic management programs to restore the health of ailing landscapes. When the conventional strategy of adding more water, fertilizers, and pesticides to their dying boxwood hedges proved ineffective, the Kennedy Greenway Conservancy in Boston hired T as a private consultant. He soon discovered that the soil, recently disrupted by construction, had very poor natural nutrient cycling and was therefore unable to retain nutrients and nourish plants. Consequently, the boxwood root systems had weakened. T helped the Greenway Conservancy horticultural staff brew a bacteria- and protozoa-rich compost tea, which they injected into the soil.

Beneficial bacteria incorporate nitrogen into their biomass, preventing it from leaching out of the soil. Protozoa feed on these bacteria, metabolizing their carbon and nitrogen content at a ratio of 30:1. They release excess nitrogen as ammonium (NH₄) waste, a form readily utilized by plants. Their roots, in turn, exude substances that nourish bacterial populations. As the compost tea reestablished this natural nutrient cycle in the Kennedy Greenway Conservancy soil, the shrubs rapidly regained their health. Within two months, Boston enjoyed green, vigorous boxwoods in its newest park.

Gardener Nicole Lewis helps T prepare compost samples for biological content testing. photo credit: C. Robertson

Though T is skilled with advanced monitoring and testing equipment, he maintains that the best diagnostic tools are a spade, a soil corer, and his hands, nose, and eyes. Rubbing dirt from each of the three zones between his fingers and carefully examining its color, T made an estimate of the soil texture (the ratio of sand to silt to clay present) that almost exactly matched the UMass lab results: silt loam in the upper and lower thirds and loam in the middle.

Explaining that a very silty soil is an obstacle to easy infiltration, T was not surprised to hear that our cation exchange capacity (CEC) levels are low. CEC is a measure of the soil’s ability to retain and supply negatively charged nutrients such as calcium, magnesium, and potassium to plant roots. These nutrients cling to finely divided organic matter and clay particles in the soil. The microbes added to the soil in the liquid biological amendment (compost tea) will mitigate the effects of our low CEC by fixing these nutrients in their bodies. If their contribution is still not sufficient, we will add bulk compost to raise the level of organic matter present. The success of both efforts relies entirely on the quality of the compost we produce.

Casey Sclar, Ph.D. Plant Health Care Leader at Longwood Gardens, inspects a handful of compost from Swarthmore’s windrow at the municipal compost facilities. photo credit: C. Robertson

At the municipal compost facility, T and the other turf specialists reached into the middle of the maturing windrows, feeling the heat of the pile and extracting a handful of the rich, decomposing material for closer examination. In order to kill any weed seeds that might be mixed into the compost, the heap needs to be kept at a temperature of over 130º Fahrenheit for at least two weeks. If it strays above 160º, however, or does not receive enough air, anaerobic conditions alter the biodegradation process. The simplest method of detecting anaerobic compost, T taught us, is by smelling it: its hydrogen sulfide byproducts produce a scent similar to rotting eggs.

T, professors, Sustainability Committee members, turf specialists, and staff participate in a round-table discussion over lunch. photo credit: C. Robertson

In addition to discussing the technical details of our program, we also engaged T in a planning session on the study and documentation of our lawn care transition. Several professors and college community members joined us for lunch in a dialogue about prospective research projects, curricular tie-ins, and institutional assimilation. They entered a vigorous discussion about the feasibility and value of a scientifically rigorous approach versus a more qualitative life cycle assessment or demonstrative study. Regardless of which experimental design proves most suitable, we plan on monitoring changes in root development, thatch volume, turf density, soil compaction, irrigation requirements, and nitrates, phosphates, and pH levels in the soil and surface runoff. I will work with other students, faculty, and specialists to develop appropriate and replicable techniques to gather and analyze this data.

Examples of new equipment for the organic lawn project. From top to bottom: an Aeravator, lysimeter and hand pump, and a solar-powered rotary composter.

Based on T’s preliminary feedback and recommendations, the Grounds Department will begin researching and acquiring specific equipment, such as a pump for the compost tea brewer and an Aeravator to fracture deeply compacted soil with thin, vibrating metal tines. Andy Bastian ‘12, an intern with the Engineering Department, is hard at work assembling and modifying the design of two solar powered compost tumblers. Professor Carr Everbach is helping me calibrate and install a set of lysimeters to collect soil water samples to look at nutrient levels at different depths in the soil. By the time T returns in the early fall, our capacity to carry out and monitor an organic lawn care program will be significantly greater!

To learn more about T’s work, consider joining the Arboretum trip to Battery Park City Parks Conservancy on October 6^th or attending his next lecture here at Swarthmore at the Perennial Plants Conference on October 15th.

In the fall 2009, a New York Times article about an innovative organic lawn care project at Harvard University shook the assumptions of other higher education institutions regarding their own landscaping practices. A casual inquiry about Swarthmore’s lawn management by an alumnus who had read the piece sparked a flurry of discussion and activity that will culminate this fall in the implementation of the Scott Arboretum’s first organically maintained lawn.

Instead of applying standard synthetic herbicides and fertilizers to the five-acre field between Mertz dormitory and Magill Walk, gardeners will spread compost and spray compost tea. This organic matter will be carefully prepared and monitored to contain a balance of nutrients that fully nourish the soil, the microorganisms that dwell within it and, in turn, the grass. We currently use organic fertilizers and practice integrated pest management as a part of sustainability efforts. This summer we will begin testing organic lawn practices.

Based on favorable results at Harvard, we hope that our new lawn will improve the health of the turf and local ecosystem, minimize environmental impact by reducing mowing and irrigation needs, and offer a cost-saving alternative to conventional lawn care. Since the new approach requires closer monitoring and ongoing program adjustments, labor costs will rise; the cost of purchased supplies, however, will decrease. A project on a New York football field showed that once established, organic lawns can be 25% less expensive to maintain!

“A comparison of costs (dollars) for conventional and natural turf programs over a five-year period, based on data collected and analyzed by Charles Osborne and Doug Wood, Grassroots Environmental Education 2010.”

Next month, Eric T. Fleisher, the coordinator of Harvard’s organic turf program, will visit our campus to tailor his compost tea recipes, application schedules, and aeration techniques to the specific needs of our site.

A rising sophomore and student liaison to the Sustainability Committee this past spring, I received a grant from the Lang Center to work on the lawn care project with Grounds and the Arboretum. My first task was to run the diagnostic tests identifying the present makeup of the soil and turf upon which T. Fleisher will base his recommendations. Using the procedures that he prescribed, I have spent the past few weeks preparing soil samples for lab analysis and conducting percolation tests to determine the rate at which the soil is able to absorb water.

Camille Robertson digging soil samples to send in for laboratory testing. photo credit: N. Lewis

We have to wait for the UMass Amherst Soil Testing Laboratory to get back to us to learn the concentrations of organic matter and extractable nutrients, the soil texture, and the level of soluble salts in the soil, but the percolation tests returned immediate results.

Satellite image of Mertz field taken in 2008 during the construction of David Kemp Residence Hall. photo credit: Google Maps

To account for potential differences among the rates at which water infiltrates into the soil at different depths, I dug three foot-wide holes 6”, 12”, and 18” deep respectively. I then roughed the edges of each hole (so that water enters the soil as “naturally” as possible), lined the bottoms with sand (minimizing splashing, also a potentially confounding factor), and saturated the soil to control for dryness (making tests run the day after a rain comparable to those done in the middle of a drought). After completing these preparations, I filled the holes with water and checked them frequently over the next 12 hours, recording the height of the water column. Noting how quickly the water level drops allows us to infer the porosity of the soil—a more porous soil provides many channels for water, organisms, and roots to pass—an important factor in stormwater retention and turf health.

The 18” hole on Upper Mertz, 15 hours after the percolation test began. photo credit: C. Robertson

A healthy lawn percolates at one to two inches per hour. I conducted the three-hole test in each of three distinct zones of Mertz lawn; only the moist lowermost region drained this quickly. Since the second zone was subject to severe compaction by heavy machinery during the construction of the David Kemp Residence Hall in 2008, percolation rates were especially low there. Water infiltrated at only half an inch per hour. The upper zone, everything uphill of the old laydown area, exhibited intermediate characteristics.

I noticed other differences between the soils in each zone simply by feeling how hard it was to dig (the rocky Middle Mertz required a pickaxe), the general consistency and moistness (Upper Mertz was damper than Middle Mertz but drier than Lower Mertz), and the number and kinds of organisms I came across in the soil (so many earthworms in Lower Mertz!).

Understanding what creates a healthy soil ecosystem is the key to cultivating a thriving green lawn. The results of our diagnostic tests and observations will allow us to design an organic lawn care program that continues our tradition as “the most beautiful campus in the United States.”

Campers from the Chester Children’s Chorus play baseball on Mertz field. photo credit: C. Robertson

Our motivation behind this non-conventional approach lies in the bigger picture—fostering the health of the Crum Creek watershed and its human inhabitants. The college and Arboretum have always strived to be responsible stewards of both by following conventional best practices. But as Rachel Carson taught us, the unintended consequences of one decade’s practices may not become apparent until the next—some health effects of the chemicals we apply could take generations to become apparent, for example. Repercussions of our dependence on petroleum-based products will be magnified when the energy crisis truly sets in. In order to keep our community and environment healthy and sustainable, therefore, we are excited to push forward to tomorrow’s innovation: organic lawns! Check back with Garden Seeds as we describe our progress in developing an organic lawn maintenance program.

After the large snow fall we had on February 5^th and 6^th you have probably looked outside and have observed many of your prized plants are engulfed in snow.  In most cases the snow will fall off the plants and they will spring back to their natural and original shape.  However, there are some plants which are especially vulnerable to heavy snows.  Several pines including the lacebark pine (Pinus bungeana) and especially the Eastern white pine (Pinus strobus) can have large branches snapping off at the trunk from the weight of the snow.

Most evergreen conifers, however, that have a strong central leader, such as: Japanese red-cedar (Cryptomeria); fir (Abies); spruce  (Picea); and cedar  (Cedrus) can be covered in snow without it causing a serious effect.  Multiple trunked conifers, such as, juniper (Juniperus); Leyland cypress  (xCuprocyparis) and arborvitae (Thuja) often have the multiple leaders splay open in a heavy snow.  In the case of the aforementioned conifers , it is advantageous to try to knock the snow from the branches to avoid the leaders from splaying open.  The damage can be irreparable from a heavy snow load.

Pinus mugo ' Enci' in the John W. Nason garden after an inch snow on February 3. photo credit: R. Robert

Most shrubs have an amazing capacity to recover from very heavy snows.  Multi-stemmed broadleaved evergreens such as inkberry (Ilex glabra);  heavenly bamboo (Nandina domestica); common boxwood (Buxus sempervirens); Mahonia japonica; and M. bealei “catch” the snow.  This often causes the branches to open up and be pinned to the ground with the weight of the snow.  If you are fearful that the weight of the snow may be doing damage,  gently brush the snow from the plants with a broom.  However, I have found that allowing the snow to melt and alleviate the weight, the plants will spring back without any permanent damage to their structure.

The same Pinus mugo 'Enci' as pictured above after a 28.2 snow on February 6. The branches are splayed open from snow load. Hopefully this plant will spring back after snow melt. photo credit: R. Robert

All perennials will be perfectly fine under the layer of snow.  Even newly emerging flowers such as the Lenten rose (Helleborus xhybridus) will be insulated by the snow and flower in profusion once the snow has melted.

Once the snow begins to melt gardeners should be mindful of snow and giant icicles melting from roofs and dislodging with great force and weight. This can often crush the plants below.  Unfortunately, like the large breaking branches of the lacebark pine and the Eastern white pine there is not a lot that can be done to avoid is collateral damage. However, I suggest don’t park your car under a white pine during a snow storm!

Last week Yvonne Post’s lead goats, Wyeth and Rodin, visited the Scott Arboretum on a reconnaissance mission. As lead goats, Wyeth and Rodin (named for famous artists) are brought to trial new locations and vegetation to see if the entire herd would take to the site and eat the weeds found there.

Rodin chomping on ivy while Yvonne discusses goats in the garden. photo credit: R. Robert

Like many other institutions in the region, the Scott Arboretum is trialing the use of goats to remove invasive and stubborn weeds from the garden. Also called “nature’s weed-eaters”, goats are a sustainable, environment friendly way to treat weed infestations as opposed to chemical treatments.

Wyeth munching on ivy and leaves. photo credit: R. Robert

Post’s herd of six wethers, castrated male goats, have already begun removing Canada thistle, Cirsium canadense, at Bartram’s Garden. The herd is also hoping to visit Longwood Gardens to help remove garlic mustard, Alliaria officinalis. Post has described how they delight at eating mile-a-minute vine, Polygonum perfoliatum, on her property. Here at the Scott Arboretum, we are working on removing English ivy, Hedera helix.

This trail evaluated whether the goats will eat the ivy blanketing the banks of the Crum Woods or whether they would graze on other plant material. We are happy to report that after settling into their new surroundings in the woods, Wyeth and Rodin blissfully chomped away on ivy and fallen leaves. The complete herd of Angora goats will return this January to begin foraging on the ivy in earnest.

Goats are more effective at weed removal than other grazers, such as sheep. Goats rip and pull the plants out by the roots when they forage, as compared to sheep who simply graze the tops of the plants, leaving the roots intact. Post recommends having the goats for three consecutive years to see true effect on a weed patch.

Rodin and Wyeth over looking the smorgasbord of ivy. photo credit: R. Robert

Goats prefer to feed on different plants at various times of year. As Post explains, “They get bored.” As you can image with ability to eat such a variety of food, you would like to spice up your diet too. They enjoy the young shoots for Canada thistle in the spring, mile-a-minute vine in the summer, and fallen leaves and weedy grasses in the fall. For this reason, the herd will visit the Scott Arboretum in the winter feeding on the smorgasbord of ivy. This way the herd will not be distracted by more choice plants found during warm months and allowing them to focus on controlling our English ivy infestation.

On Thursday, October 22 over 35 volunteers from Swarthmore College, Scott Arboretum, and CRC Watershed Association gathered to plant 83 trees and shrubs. These plantings were the result of a TreeVitalize Watershed Grant awarded from Pennsylvania Horticultural Society (PHS) and Delaware County Conservation District (DCCD). Volunteers spent the morning planting a 2,000 square feet or 4.59 acre riparian forest buffer along the Crum Creek corridor.

Tools and plants are laid out in preparation for volunteers. photo credit: R. Maurer

These plantings were in addition to the trees planted last spring by Swarthmore College volunteers in the area newly name Roger’s Grove, which is the area south of the train tressel. These efforts are part of a study done by the biology department, professor Jose-Luis Machado, delineating knotweed populations and lacking native plant buffer.

Along this corridor of the Crum Creek, the invasive knotweed, Polygonum cuspidatum, forms dense thickets that exclude native vegetation. As a riparian area (an ecosystem that occurs along a watercourse or water body), the banks of the Crum Creek are under significant threat from knotweed because it can survive floods and then rapidly colonize scoured shores before native vegetation can establish.

Polygonum cuspidatum is an upright, shrublike, herbaceous perennial that can grow to over 10 feet in height. It produces minute greenish-white flowers that occur in attractive, branched sprays in summer and are followed by small winged fruits. The root system consists of long, stout rhizomes.

The brown stand of plants behind the volunteers is treated knotweed along the creek bank. photo credit: R. Maurer

Because of these rhizome roots, knotweed should not be removed by digging up the plants. The rhizomes will simply break or be cut apart creating new plants. In order to control the population along the Crum Creek, glyphosate (an herbicide) was applied twice to the foliage of the plants, once in the late summer and another in early fall.

Volunteers planting the riparian forest buffer. photo credit: R. Maurer

Volunteers then planted the riparian forest buffer with native species to shade out and, once established, out compete the knotweed adjacent to treated to treated populations of plants. Bryn Richard, a local landscape architect, selected the native plants according to the Wetland Indicator Status from the USDA plant database.

Anne Murphy and Bryn Richard of CRC Watershed teaching volunteers proper planting techniques with a weed mat. photo credit: R. Maurer

This indicator identifies if a plant occurs almost always, likely, usually, or equally likely in a wetland. From this indictor Byrn located native plants closer, further, or on a raise adjacent to the creek bank. See the complete list of plants and their indicator below.

If you visit this new planting, you will notice they are planted in rows 15 to 20 feet apart. Many of you may notice this is opposite of what is recommended to homeowners. The rows are to allow mowing of the meadow two to three times a year until the plants are established. They were also planted close together to quickly create a canopy of shade to shade out the knotweed.

Tube protecting a tulip poplar from deer damage. photo credit: R. Maurer

These young plants were also planted with a weed mat to discourage weeds, and a deer cage or tube to prevent additional damage. Once the plants reach an appropriate size volunteers from the CRC Watershed Association will remove the cages and mats.

If you have a canopy of knotweed growing along a bank near you, you can apply for a 2010 Southeast PA TreeVitalize Watersheds Grant Program. Applications are due to the Delaware Co. Conservation District before Friday, November 13th.

Thank you to all the volunteers, Bryn Richard, Anne Murphy, and CRC Watershed Association for helping to make this project a reality. And of course to PHS and DCCD for providing the support for this restorative effort.

Propagating cacti can seem like a daunting task, but with a good pair of gloves it is a simple process. It is recommended that you propagate your cacti in late spring with the arrival of warmer, drier weather. This allows plants plenty of time to get established before the winter season. You will need a pair of pruners and the aforementioned gloves.

The many sized spines of Opuntia. photo credit: R. Robert

The gloves, of course, provide protection from the prickly spines that are a trademark of all cacti. Be warned, while the average new cacti grower avoids the large, fearsome spines, the tiny, fine thorns cause the most pain. These almost microscopic thorns stick in all manner of clothing, causing continual pocks and pricks. If you do fall victim to their touch, you may be able to remove them by applying masking tape to the pull the thorns out. If your attire becomes severely entangled by these thorns, you simply have to discard the afflicted article of clothing. There are many war stories of having to discard various pairs of socks and pants because of these tiny menaces. Thus approach your cacti with great caution.

Newly cut cacti pad. photo credit: R. Robert

Properly equipped with gloves, simply use your clean, sharp pruners to remove a pad where a joint forms with another pad. If you are sharing your pads with friends, simply wrap the pad in newspaper to give to a friend. The newspaper makes sharing easier and less prickly. Store the pad in a dry location until ready to plant. No other care is required.

Wrapping the pad in newspaper. photo credit: R. Robert

Before planting, choose the appropriate location for your cacti. It should be a sunny, well-drained to dry location. It is recommended that you mix some gravel into your cacti garden soil to encourage good drainage and increase the porosity of that soil.

Planting the pad into the garden. photo credit: R. Robert

To plant your cacti cutting, place the pad upright in your garden or lay it on its side. Be sure to have the cut portion of the pad slightly touching the soil to stimulate rooting. No other care is necessary. You can also cut the pad in half to increase the number cacti you have. As a good gardener, you may be tempted to water the newly planted pad. Watering can cause the pad to simply rot. It will be happy with a sunny, dry location and no attention at all.

A piece of Opuntia broken by the elements of nature. photo credit: R. Robert

This simple method of propagation mimics the conditions in the wild. Pads are often broken off and carried along by animals. Once a pad is broken off or is dropped by the animal on the ground, it will begin producing roots from the point of the break.

Consider adding these prickly beauties to your garden. Visit the Scott Arboretum see the variety of hardy cacti for the Delaware Valley.

Last summer in an attempt to become more environmentally friendly we replaced our gas-powered mower with a Brill RazorCut Premium 33 Reel Mower. The spinning blade of the reel mower works purely from the power of whoever is pushing it. In the beginning, this mower served our needs very nicely. We relied on it for mowing the lawns in both the Entrance Garden and the Terry Shane Teaching Garden. The reel mower worked beautifully when the lawn had been mowed weekly and there was no debris in the lawn.

We started to have problems with this mower when we received a lot of rain. Because of the rain we were unable to mow as frequently as we like and the lawn got longer than we would normally allow it to. This caused the spinning blades to get clogged up.

During the fall and at other times of the year when leaves, twigs, and beech capsules would get fall onto the lawn, they would cause the blades to jam. So, this year we began to look for a more reliable alternative to the reel mower.

Curatorial intern, Sam Keitch, using the Arboretum's electric mower. photo credit: Andrew Bunting

My friend and colleague, Robert Herald had told me that he had purchased a cordless electric mower. While visiting his garden in Swarthmore, he demonstrated the use of this new mower. I was impressed at how well it cut, how easy it was to start, and how relatively quiet it was compared to a gas-powered mower. The brand and model he bought was the Black and Decker 24-amp, 19″, Cordless Electric Push. We ended up purchasing the same model for $359.00. Its operation is very simple: plug it in, charge it overnight, unplug the cord, press the starter handle, and mow. You don’t have to pull a cord to get it started. It does come with a bag for the clippings, but we have decided to use it as a mulching mower thus returning the clippings to the lawn as organic matter.

During the month of June, gardens all over the greater Philadelphia area are celebrating the World’s Largest Garden Party. With graduation and father’s day celebrations, you may find yourself holding a garden party this month too. Here are some tips and tricks that we use at the Scott Arboretum when throwing parties in our gardens.

Garden Party in the Pollinators Garden. photo credit: R. Robert

Day Before:

1. Mow your lawn at least one day before your party. Mowing the lawn stirs up a lot of allergies for many people and doing so the day before will prevent guests from sneezing throughout your celebration. It will also prevent guests from dragging grass clipping throughout your house, most notably into your bathroom.

2. Tuck away garden hoses and tools, as they pose a tripping hazard to your guests.

Day of:

3. Place your food tables as close to your kitchen as possible. This will save you time and energy when replenishing snacks and drinks.

4. Keep bugs away with citronella candles and bounce sheets around food and seating areas.

5. Create floral arrangements from the blooms in your garden. In the event of rain, using flowers from your garden helps to bring it inside for guests to enjoy.

Enjoying the flower arrangement made from flowers in bloom in the garden. photo credit: S. Edelson

These tips will help ensure garden party success. Come celebrate the World’s Largest Garden with the Scott Arboretum tonight for Sunset Sippin’: White Roses and Whirlwind Wit. Despite the rain, enjoy the scents of white roses, the company of friends, and the flavors of Whirlwind Wit from Victory Brewery. The refreshing interpretation of this classic, Belgian “white beer” and the striking beauty of white roses will combine for a lovely summer evening.

This week with severe thunderstorms, spontaneous downpours, and overflowing storm drains, it has reinforced the importance of storm water management. It is important to prevent as much runoff from storm water on your property as possible to allow for the replenishment of ground water and prevent erosion of local streambeds.

Rain water runoff carries not only topsoil, but fertilizers, pesticides, oils, and other pollutants into the surrounding creeks and streams. Once in our waterways, these contaminants cloud the water, stress aquatic life, and disrupt stream habitats.

Digging the trench for the cistern. photo credit: R. Robert

The Scott Arboretum and Swarthmore College’s latest effort to reduce rainwater runoff is the installation of a 7,000 gallon cistern behind the Wister Education Center and Greenhouse. The rainwater is collected through the gutter system of Wister Center and the rear gutter system of Cummingham House (Scott Arboretum Offices) into the tank.

This water will then be used to irrigate the gardens around Wister Center. Overflow from the cistern will be discharged in the BioStream, another storm water management effort. This installation is another component of our efforts to receive silver LEED certification for the Wister Center.

Rain barrel in Terry Shane Teaching Garden. photo credit: R. Robert

You can collect the runoff from your own property with a rain barrel and, in turn, use the collected water to irrigate your containers and garden. In areas where you have standing water or flowing water during a storm, you might consider planting a rain garden, such as the BioStream, to allow runoff to infiltrate back into the ground.

As I see more and more people getting busy in their gardens, and crews of landscapers busy mulching trees in parks, along streets and at local businesses, this is a good time to revisit the reason for mulching woody plants and the proper method to do so.

Benefits

Trees planted in urbanized or developed environments such as city parks, near roads or buildings, or in cultivated gardens or lawns are often exposed to stresses not usually found in woodlands or natural environments. We remove the natural source of nutrients available to plants when we rake leaves, remove topsoil from construction sites and tidy up our gardens: decaying organic debris.

Magnolia stellata 'Centennial' correctly mulched. photo credit. R. Maurer

Plants do not care about what form of nutrients they receive, whether organic or inorganic, since they use nutrients in their elementary form. But there are many benefits to using an organic source:

• Lessened impact to the environment
• Contributions to the local economy and waste management systems
• Most composted materials contain significant quantities of the major plant nutrients and a full range of micronutrients and trace elements not often found in inorganic sources

Most urban trees simply need a periodic application of composted mulch to meet their basic fertilization requirements. The organic matter in composted mulch is able to give many benefits in addition to acting as a slow-release fertilizer:

• Improved water holding capacity and moisture conservation
• Increased microbial activity, which contributes to plant disease suppression and improved nutrient cycling
• Improved root growth
• Reduction in soil compaction and erosion control
• Save herbicide costs and reduce the competition caused by weeds

Incorrect technique of telephone pole affect on a tree trunk in a "Mulch Volcano". photo credit: R. Maurer

Types to Avoid

Many bark mulches, playground bark, or bark chips are not composted. According to Ronda Koski and William R. Jacobi of the International Society of Arboriculture (ISA), bark chips are commonly derived from landscape trees that were removed because of poor health and often contain plant pests. Chips derived from pallets and other wood packing materials may harbor indigenous and exotic plant pathogens. Composting breaks down these pathogens, so it is very important to use mulch that has been composted for at least one year. At the Scott Arboretum, we prefer a mixture of composted leaves and composted bark as a mulching material for trees.

This "Mulch Volcano" is over a foot tall on a tree planted approximately 5 years ago. photo credit: R. Maurer

Technique

While you will not over-apply nutrients by over-applying composted mulch, you can expect other problems. Therefore it is best to apply composted mulch no deeper than 2 to 4 inches extending at least to the canopy drip line (roots actually extend well beyond this point). Do not pile mulch around tree or shrub trunks; the trunk flare and root crown should remain exposed.

"Mulch Volcano" over 2 feet tall downhill. photo credit: R. Maurer

“Mulch volcanoes” where mulch is piled up around tree trunks resembling a cone seems to becoming a common site. But this practice promotes many problems.

• Leads to excessive soil moisture and potential root rot
• Causes inner bark tissue to die due to lack of oxygen
• Leads to insect and disease problems due to the specimen being under stress
• Creates a habitat for rodents that chew on the bark and girdle the stem
• Leads to anaerobic conditions that produce alcohols and organic acids toxic to young plants and create imbalances in soil pH

After excavating a "Mulch Volcano" 6+ inches deep, the root flare is still not visible. photo credit: R. Maurer

Mulching deeply around the trunk causes a slow decline and eventual mortality of woody plants. People are wasting money, labor and mulch in the short term and wasting the potential of magnificent specimens in their landscapes in the future.

Early signs of trunk rot and decline due to "Mulch Volcano". photo credit: R. Maurer

Links for further information:

Top 10 Myths of Tree Care – ISA (International Society of Arboriculture)

http://www.treesaregood.com/pressrelease/press/top10myths.aspx

Proper Mulching Techniques Key to Healthy Trees – ISA

http://www.treesaregood.com/pressrelease/press/MulchPR.aspx

New Tree Planting – ISA

http://www.treesaregood.com/treecare/tree_planting.aspx