Tree Restoration Plan shapes future of Tower Grove Park

A new plan that will guide the location and species of hundreds of trees to be planted in Tower Grove Park in the next few years, which will shape the Park for decades to come.

The new Tree Restoration Master Plan will help balance the Park's 150 year history, with the need to face current needs and future challenges in all decisions related to tree planting and removal.

Trees are one of the defining features of the Park, and one of the reasons it is has been a beloved oasis in the heart of St. Louis for 150 years. Tower Grove Park is a Level II Accredited Arboretum through ArbNet.

The Park is also a National Historic Landmark, partly because of its unique Gardenesque style. Park founder Henry Shaw designed the Park with this style, which purposefully guides visitors and focuses on showcasing the unique attributes of the Park's horticulture and trees.

“We’re one of the few parks in the United States that uses the Gardenesque style,” Executive Director Bill Reininger explained. “This plan reinforces the original vision.”

Inspiration for developing this plan

The development of a tree master plan was recommended in the Park's 2017 Master Plan.

When the Park received a generous donation from the Mysun Charitable Foundation in 2020 to plant 1,000 new trees over five years, Park leadership saw the perfect opportunity to pursue the plan to address the current state of the Park’s canopy, and thoughtfully consider what trees should be planted and where.

With funding from the Missouri Department of Conservation Tree Resource Improvement and Maintenance (TRIM) Grant and additional funding from a private donor, the Park worked with a local landscape architecture firm, SWT Design, for the past nine months to create the Tree Restoration Plan.

An analysis of the past and present

SWT Design began its work with a study of the Park’s history and an analysis of the current state of the canopy.

Nearly 7,000 trees of more than 350 species make up the Park's current canopy, covering approximately 44% of the park, based on recent aerial photography. 

The condition of a tree is judged on a six-point scale – Excellent, Good, Fair, Poor, Critical, and Dead. Unfortunately, nearly half of the Park’s trees are currently considered to be in fair or poor condition.

The study showed that the canopy is experiencing a steady decline, due to numerous factors including climate change, pests, disease, age, and more. The plan's executive summary states, "Without a concerted effort to address this situation and anticipate ongoing changes, the Park's canopy will continue to decline at a faster rate than it can be replaced.”

“Many of the challenges we are seeing today in the canopy stem from both structural deficiencies within the trees as well as pests and diseases,” said Kevin McIntyre, forestry supervisor. “Those challenges are being compounded by climate change through more severe storms and better conditions for pests and diseases to flourish.”

McIntyre pointed to significant damage suffered in storms the past few years. “It’s a reminder that many trees within the park are at a tipping point. If the trees keep on in their current trajectory, the park will exponentially lose more trees as the years go on.”

He said that the Park has been able to invest more into tree maintenance with the development of a plant healthcare program, more pruning, cabling and bracing trees, and even reusing much of the wood waste.

“With this plan in place, we will be able to ensure that the Park’s trees will be able to better withstand these stronger storms and pests and diseases,” McIntyre said. That will allow McIntyre’s team to focus its efforts on pruning and plant healthcare, which will ultimately make the trees “more resilient, healthy and aesthetically pleasing.”

Putting the plan into action

Before 100 trees in a 5-acre zone near the Turkish Pavilion could be planted, trees in the area with a poor rating had to be removed. This zone has the highest concentration of trees in poor condition in the Park. In March, the Park’s Foresty team removed 38 trees in the zone rated in poor condition.

Internal structural defects in the trees that have been removed have confirmed the rating in every case.

“Many trees exhibited poor structure that would've been challenging to remediate via pruning, as well as evidence of pests and diseases that have caused significant dieback within many of the trees, and mortality in others,” McIntyre said. “Many of the oaks that we have removed had been hit hard by Hypoxylon, most to the point that we could remove limbs the size of our legs by our hands alone.”

By proactively removing these trees now, the chance for failure during a storm or at a random time is decreased, which will not only improve safety for Park visitors, but also place less of a toll on the Park’s Operations teams.

“We are not taking out healthy trees,” Reininger said, adding that no trees in excellent or good condition will be removed.

Next, the Forestry team will work in the southeast corner of the Park near the Stupp Center, then will move on to restore a historic “allee” on the path from the Cemetery Gate pedestrian entrance near Spring Avenue.

“From there, we will continue to work our way through zones, removing one year and re-planting the next,” said William Rein, Director of Operations and Special Projects, explaining that the approach will allow the Park to stay efficient with watering the newly planted trees.

Future plantings in the Park

SWT Design’s study found that there are currently 21 species that represent 52% of the Park’s total canopy. To promote greater diversity among the Park’s trees, the plan recommends that a single species should not exceed more than 1% of the total canopy, and cultivars should not exceed 50% of a given species represented.

"History has shown that a lack of diversity in trees can lead to tremendous issues if a pathogen or insect becomes problematic," Reininger said.

In addition to studying historical documents and analyzing current data about the Park’s trees, the planning team from SWT Design made onsite assessments and met with an advisory panel of tree experts to discuss recommendations for future plantings.

The panel assembled a list of 88 species or cultivars for future use in the Park that will help bring more diversity to the Park’s tree selection.

The new selection of trees will also feature a greater variety of species that have traditionally been planted in warmer climates south of Missouri, which will fare better as average temperatures increase in this region.

With all of this information, SWT Design created the plan that lays our four primary goals:

1. Re-establish the historic tree layout

2. Promote diversity of tree species

3. Reduce species in decline

4. Maintain canopy cover

A key element of this plan includes a process and toolkit for selecting priority tree species and balancing the overall composition of the park’s tree diversity. It also provides intentional guidance about the Park’s typography, defining the purpose for all areas of the Park. This will provide standards for species options and locations for all future plantings.

The plan will also ensure that past placement mistakes are not repeated.  In some instances, trees were planted in spaces that were meant to be open. The plan states, "In Shaw’s vision for the park, the open areas were as critical to experience the plant collections as the plants themselves.

The plan’s legacy

The plan outlines three years of activity, but will be preparing the Park for decades into the future.

“The thing about trees is that they are always planted for future generations,” Rein said. “Many of our oaks take 30 years to mature, so what we’re doing now won’t really become evident until decades from now.”

Henry Shaw’s 1875 plan for Tower Grove Park

Reininger called the Tree Restoration Master Plan a 100-year plan.

“The plan will have some of the most profound and long lasting effects on the Park in my tenure,” he said.