Viburnum rhytidophyllum ‘Cree’ in fruit behind Parrish Hall. photo credit: J. Coceano

Heuchera ‘Midnight Bayou’  located on the North side of Kohlberg Hall. photo credit: J. Coceano

Callicarpa dichotoma in fruit at the West Garden. photo credit: J. Coceano

Hydrangea paniculata “Kyushu’ in the Hydrangea Collection. photo credit: J. Coceano

Our curator, Andrew Bunting, is always planting unusual tropicals and annuals in the Scott Entrance Garden for a unique display during the summer and fall. An annual which has caught my attention this season is Mirabilis jalapa. While not of note during the typical work day, I have been lucky enough to catch this plant creating a charming display just before our work day begins at 8:30 am. Known as the four o’clock flower, Mirabilis jalapa typically opens its trumpet-shaped flowers during the evening hours.

The closed and wilted blooms of Mirabilis jalapa, as seen during the day. photo credit: R. Robert

This two-to three-foot tall, trouble-free plant is covered in blooms during the evening, then its flowers wilt the next morning. This transition is not unattractive during the day, because of the number of closed flowers present on the plant. You may occasionally have open flowers during the day, i.e. a rainy day, because the opening and closing of the blooms is temperature sensitive.  These delightful plants will bloom from summer to fall with little to no care.

Mirabilis jalapa in the Scott Entrance Garden. photo credit: R. Robert

Flower colors vary between red, magenta, pink, yellow, white, and bicolor. A native of South America, this plant has naturalized in some southern gardens. In our region, some gardeners may recall this annual in their grandmother’s garden. Visit the Scott Arboretum in the evening to enjoy the lovely display of the four o’clock flower.

This summer saw the removal of the last Malus tschonoskii on campus. As part of our mission to display great plants for Delaware Valley gardeners, we trial new introductions and cultivars of plants. Beginning in the 1980s, Scott Arboretum participated in the National Crabapple Evaluation Program led by Professor Les Nichols of Penn State University.  This program evaluated readily available crabapple cultivars in various locations throughout the United States based mainly on disease resistance and aesthetic autumn appeal.

The last Malus tschonoskii on campus has succumb to fire blight. photo credit: R. Robert

Malus tschonoskii was among the over 50 species and cultivars evaluated for 4 years during the 1990s. It was confirmed that the Tschonoskii crabapple is highly susceptible to fire blight. Fire blight is caused by a bacteria (Erwinia amylovora) which attacks the blossoms or flowers and then moves up twigs into the branches. It creates a burnt appearance on the flowers, foliage, and twigs. Plants in the Rosacea family (i.e. roses, apples, and pears) are highly susceptible to this disease.

Fall fruit of Malus 'Indian Magic'. photo credit: R. Robert

With the last specimen of Tschonoskii crabapple wholly succumbing to fire blight, it was removed from the collection as unsuitable for gardens in the Delaware Valley. This study did reveal that Malus ‘Donald Wyman’, Malus Molten Lava®, and Malus ‘ Indian Magic’ are great crabapples for disease resistance, flower display, fall color, and great plants for Delaware Valley gardens. To experience more crabapples, visit the Scott Arboretum crabapple collection located below Cunningham Fields.

Salvia guaranitica ‘Black and Blue’ blooming in the Theresa Lang Fragrance Garden. photo credit: J. Coceano

Alocasia plumbaea in the Terry Shane Teaching Garden. photo credit: J. Coceano

Clematis integrifolia blooming in Scott Entrance Garden. photo credit: J. Coceano

Sinojackia xylocarpa in fruit at the West Garden. photo credit: J. Coceano

A stroll along the Magill Walk in early August is bound to yield a pleasant surprise.  Under the towering canopy of swamp white oaks, Quercus bicolor, bursts forth Lycoris squamigera.  This event seems to happen overnight.  The sudden emergence and explosion of bloom is reflected in several fun common names: surprise lily, resurrection lily, magic lily, and even naked ladies.  The genus Lycoris is named for Marc Antony’s actress mistress.

L. squamigera flowers and stalks. photo credit: J. Coceano

A member of the Amaryllidaceae family, Lycoris squamigera, produces pink blooms bearing similarities to that of the common holiday amaryllis. The multitude of common names originates from the bulbs unique growth habit.  In spring, the leaves sprout and grow, only to disappear as summer sets in.  Then, in late July or early August, leafless flower stalks emerge.  Emergence to flower occurs in the span of days.  The 2 ft stems typically bear 6-8 flowers.

Lycoris squamigera in bloom along Magill Walk. photo credit: R. Robert

Lycoris squamigera is a welcome sight at the height of summer.  The bulb is easy to grow, adapting to most soil types.  Provide full sun to partial shade for maximum flower development.  While there are other species, in various colors, Lycoris squamigera is the hardiest flourishing in zones 5-10.  The bulbs have slender necks and should be planted a few inches below the soil surface, deeper in sandy soils or colder zones.  The surprise lily is a triploid (having 3 sets of chromosomes instead of the normal two).  The result, like that of the mule, is sterility.  The triploid nature results in fast maturing bulbs that need division every three or so years.  While summer’s heat drags both plants and people down, it is a sure harbinger of the beauty and enchantment that is the magic lily.

Campsis grandiflora ‘Morning Calm’ photo credit: J. Coceano

Solanum quitoense photo credit: J. Coceano

Eupatorium purpureum subsp. Maculatum ‘Gateway’  photo credit: J. Coceano

Euscaphis japonica photo credit: J. Coceano

If you have been on campus the last two weeks, you may have noticed a Bartlett Tree Co. spray truck parked around. They have been injecting our American elms, Ulmus americana, with Arbortet fungicide to protect them from Dutch Elm Disease, Ophiostoma ulmi.

Bartlett Tree Co. treating the American elm along railroad tracks by Sharples Drive for Dutch Elm Disease. photo credit: W. Costello

This treatment is done every two years in even numbered years. Small holes are drilled into the root flare of the tree and small nozzles connected to plastic tubing are inserted. The diluted fungicide is then injected under pressure into the sap stream of the tree to be carried throughout the tree.

Equipment used to inject fungicide into the trees. photo credit: W. Costello

Dutch Elm Disease first arrived in America in the 1920’s creating devastation through the American Elm population. This fungus attacks the vascular system of the tree and causes it to plug up the xylem and phloem. The clogged vessels cut off the flow of water and nutrients to the branches and cause the tree to wilt and die. This can happen within months or even days. Elm bark beetle is the main carrier of this fungus, although natural root grafts of closely planted trees will also spread it.

We have some very massive American elms on campus between the Scott office and McCabe Library, and along the railroad tracks by Sharples Drive. So far the treatments have been working for us.

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.

Hibiscus moscheutos ‘Lord Baltimore’ photo credit: J. Coceano

Cunninghamia lanceolata ‘Glauca’ photo credit: J. Coceano

Adina rubella photo credit: J. Coceano