Landscape Color Trials
The Landscape Color Trials and All-American Selections Display Garden feature bold sweeps of colorful annuals, tropical plants, and tender perennials. Inspiration abounds with award-winning plants, just-released annuals, and creative trellising using repurposed furniture, fences, and other recycled props.
Many of the Trial Garden’s displays have won the prestigious All-American Selections award, an honor given to plants consistently ranked the best performing in trial gardens throughout the U.S.
Callicarpa Trial
The goal of this trial is to identify strong-performing alternatives to Callicarpa dichotoma and its cultivars, which have shown a tendency to naturalize and become problematic in garden settings. This trial also seeks to explore effective propagation methods—both by seed and softwood cuttings—to determine which species and cultivars might be viable candidates for broader use and promotion in the green industry.
Groundcover Trial Research in Response to Delaware Ban
Overview
In 2022, the University of Delaware Botanic Gardens (UDBG) launched a three-year research initiative to evaluate non-invasive groundcovers as alternatives to commonly used invasive groundcovers. This work directly responded to regulatory changes in Delaware that created an urgent need for viable, researched-back replacements.
As of July 1, 2022, Hedera helix (English Ivy), Vinca minor (Lesser Periwinkle), and Pachysandra terminalis (Japanese Pachysandra) were listed as invasive by the state in Title 3 §2904, prohibiting their production, delivery, and sale in the First State.
In response, UDBG aimed to identify and promote the use of similarly performing groundcovers as replacements for the four commonly used invasive groundcovers listed on Title 3 §2904.
With our research findings, we hope to stimulate both supply and demand of alternatives through education and equip landscape professionals, master gardeners, and homeowners with viable non-invasive alternatives that perform well in a landscape setting.
Approach
This research was grounded in both controlled trials and observational test plots.
In our trial area, the performance of selected groundcovers was evaluated using randomized, side-by-side plantings to directly compare alternative species with their invasive counterparts. Soil conditions and amendments, maintenance, and watering were controlled elements of the study. Each planting was monitored monthly to assess key performance indicators including vigor, color retention, weed suppression, and susceptibility to pests and diseases.
Beyond the formal trials, the selected trialed groundcovers were also integrated into existing campus landscapes to better understand their performance in variable conditions, with competition and environmental stressors. These broader observations informed our practical recommendations for planting, maintenance, and long-term success in managed landscapes.
Impact and Outcomes
Through this work, UDBG continues to actively share its findings with both consumers and industry professionals.
These findings:
– Equip landscape professionals, growers, distributors, and homeowners with reliable non-invasive alternatives that perform well in a landscape setting.
– Provide recommendations for care and maintenance for successful establishment.
– Strengthen the availability of alternative species by encouraging production and adoption.
– Expand the plant palette with selection evaluated for both ecological responsibility and commercial viability.
Lessons Learned
UDBG will continue sharing the impact of this research through ongoing tours, signage, and educational programming. Results will be published to our website in summer of 2026, and we plan to further build on this foundation with the development of virtual site tours that highlight the locations of successful groundcover alternatives on site. To view the current location of the groundcovers used in our trial, visit our Garden Explorer.
Plants Trialed
Tiarella cordifolia
Hakonechloa macra
Asarum canadense
Polystichum arostichoides
Carex pensylanica
Pachysandra procumbens
Epimedium rubrum
Iris cristata
Packera aurea
Ceratostigma plumbaginoides
Chrysogonum virginianum
Geranium ‘Biokovo’
Sedum rupestre
Phlox subulata
Nepeta ‘Walker’s Low’
Phlox stolonifera
Hedera helix (invasive)
Pachysandra terminalis (invasive)
Vinca minor (invasive)
Lysimachia nummularia (watch list)