Maintaining the Plant Collections on the Laurel Ridge Trail and the Heathdale in Nichols Arboretum

By Amy Wells

I first fell in love with rhododendrons while visiting the Great Smoky Mountains National Park. The tall, dense shrubs boasted perfect evergreen leaves and were covered in clusters of large, showy flowers. When I began school at the University of Michigan three years ago, I was enchanted by Laurel Ridge Trail and the Heathdale in Nichols Arboretum because they reminded me of hikes through the Smokies. The Heathdale, apart from being one of the most peaceful places in the Arboretum, is also home to the Julie Norris Post Heathdale Collection. Many of the plants in the Heathdale are members of the heather family (such as rhododendron and azalea) or are found growing in the Appalchian mountains.

This summer, as an intern at Matthaei Botanical Gardens & Nichols Arboretum, I had the privilege of helping to maintain the ericaceous plant collections in the Arb, as well as collecting data that will help Arboretum managers make better planting choices in the future.

I began the summer with a list of 422 rhododendrons, azaleas, and mountain laurels in Heathdale and on the Laurel Ridge Trail. I was asked to find all of the plants, evaluate their health, and test the pH of the soil they were growing in so the plants would continue to thrive. And I sought to gather useful and complete information using methods that would be easily repeatable by future interns.

Mountain laurel (Kalmia latifolia)

Rhododendron

Rhododendron

To keep track of the plants in this large collection, maps and spreadsheets are used to catalog plantings and embossed aluminum tags give each plant a name and number. Despite the challenges and time required, it’s important for Matthaei-Nichols to keep track of the health of individual plants. Knowing where specific cultivars thrive or die can save time and money when new plantings are chosen. The Arboretum is also responsible to the donors who support the care and stewardship of its plants and plant collections.

To ensure that future plant health assessments would be comparable to mine, I worked with Arb and Gardens collections and natural areas specialist Tom O’Dell and fellow summer intern Emily Gehle on a key to describe and rank each plant’s health on a scale of one to five. Using pictures of archetypal plants from each category, I created a key to guide future interns. The health assessments will always have a qualitative aspect to them, since the line between any two ratings is a matter of opinion, but hopefully this key will impart some consistency into the process.

Assessing the health and soil pH of each plant was like a game of hide-and-seek. Fortunately, I had a great pH meter. It didn’t require me to wet the soil before testing, and it only needed a swipe with a conditioning film between each test while I waited patiently for the needle to stop. I also took light measurements from each bed, marking the locations with green flags so that subsequent readings can be done in the same place.

The plant health assessments are important for creating a stewardship plan for this area. It was also a learning process for me. For example, I noticed that one cultivar of rhododendrons, ‘Yaku Princess,’ does less well in a particular location of Laurel Ridge Trail, while other cultivars like ‘Today and Tomorrow’ do very well there.

I know that continuing to monitor and amend plant records improves the vigor of the plant collections in the Heathdale and the Laurel Ridge Trail. I look forward to returning each year in May and June to see them bloom.

Amy Wells, from Orion, MI, is a senior in the College of Literature, Science and the Arts majoring in plant biology and minoring in multidisciplinary design in the College of Engineering.