Highlights from 2025 Field Trials: Iowa Arboretum
(Information provided by Fatima Najar, Trial Program Coordinator)
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Started in 2023, the Iowa Arboretum & Gardens Trial Program serves the Central Midwest by evaluating long-term performance of perennials and shrubs in a unique climate. Plant performance information is always accessible to the public, while annual reports are shared with the industry. We are also excited to be selecting our first perennial Top Performers this fall as they wrap up their third season in the ground. This year, the arboretum had the pleasure of hosting tours for the Perennial Plant Association National Symposium held in Des Moines, IA. It was fantastic having the opportunity to showcase our trial garden plots to many plant enthusiasts, industry representatives, and learn what plants stood out to them!
In general, we like to think the design of our trial program is unique. Rather than a traditional row trial, our garden is arranged in plots, inspired by Tom Stuart Smith’s ‘Plant Library’. As plants mature in their plots, the garden is like a quilt of multicolored squares.
The goal of our trials is to evaluate the long-term performance of perennials and shrubs in a unique climate. Currently, the trial program in the Iowa Arboretum consists of 364 perennial plots and 46 shrub plots with a total area of almost a full acre for our third year of trialing. The climate in Central Iowa for this season was very wet, receiving almost 20 inches of rain in June and July. The plants were all affected differently; those that love wet feet thrived; however, we did lose some perennials and shrubs that were not a fan of the consistent heavy rains. During mid-season, we experienced more humid and hotter weather than on average, which led to plants that were doing okay to crash. Some plots also experienced temporary flooding, and we experienced high winds in August, with wind gusts reaching 60 mph. The unpredictable weather events throughout the summer affected the trial plants’ performance and appearance.
The 2025 season was our most successful year yet, with more than 60,000 visitors to the arboretum. Visitors regularly walked through the trial garden, and many say it is their favorite part of the gardens. Between the coordinator, the trialing committee, and public evaluations, the program has the most data it has ever collected in a season.
Plants That Impressed Me This Year:
Milkweed Asclepias incarnata Ice Ballet (Jelitto Seeds)
Milkweed Asclepias incarnata Ice Ballet (Jelitto Seeds) | Iowa Arboretum & Gardens
This plant is a pollinator magnet! This summer, Ice Ballet gave a floriferous show for eight weeks straight, keeping the trial garden looking alive, with the abundance of pollinator traffic noticed on these plants. It brings vibrance to the landscape, with its tall, sturdy stems that hold up well in the high winds, and its seed pods that carry interest into the fall. Ice Ballet had many Perennial Plant Association hosts intrigued, being one of the plants that many stopped to look at.
Rose Mallow Hibiscus hybrid SUMMERIFIC® ‘Edge of Night’ (Walters Gardens/ Proven Winners)
Rose Mallow Hibiscus hybrid SUMMERIFIC® ‘Edge of Night’ (Walters Gardens/ Proven Winners) | Iowa Arboretum & Gardens
Nothing gets to this plant; it has continued to shine and give excellent performance when we have had drier summers, and looked fantastic, like always, and despite the heavy rains we received this season, it looked amazing! Uniform, deep purple, almost black foliage gives brilliant contrast within the landscape all season long! Edge of Night is a two-time winner as a fan favorite, voted Public Favorite in 2024 and 2025 during our field day.
Top Six Plants Rated by the Public for 2025:
- Rose Mallow Hibiscus hybrid SUMMERIFIC® ‘Edge of Night’ (Walters Gardens/ Proven Winners)
- Black-eyed Susan Rudbeckia fulgida var. sullivantii ‘GoldBlitz’ (PanAmerican Seed)
- Panicle Hydrangea Hydrangea paniculata First Editions® Berry White (First Editions)
- Chastetree Vitex agnus-castus First Editions® Galactic Pink (First Editions)
- Ninebark Physocarpus opulifolius First Editions® Fireside (First Editions)
For more 2025 field trials information and variety highlights, click here.
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