The ferns, flowers, shrubs and grasses of Cadillac Mountain have a tough enough time surviving the elements, but the biggest threat of all may be the pounding of constant foot traffic on Acadia National Park’s busiest and highest summit.

During a recent morning atop 1,530-foot Cadillac, Jill E. Weber, a botanist who consults for the park, surveyed areas close to the summit where she and other researchers are attempting to restore and protect common Acadia plants and some rare species such as mountain firmoss, Nantucket shadbush and boreal blueberries.

“We have a lot of years with a lot of feet,” Weber said. “There is no ill intent. There just has not been the maintenance of the vegetation. A lot of it is gone and we are trying to figure out if we can bring some of it back.”

On Cadillac, which receives about 700,000 visits by people a year, the Acadia plants are as fragile as those along the well-known Alpine Garden Trail of the much higher Mount Washington in New Hampshire.

Botanists, park leaders and others are now close to completing a multi-year project to understand, protect and revive Cadillac’s fragile vegetation.

Project seeks to revive and protect Acadia plants atop Cadillac

As much as 16 percent of the Cadillac summit vegetation and soil has been damaged over the years, and about 300 “social trails,” or unofficial paths created by visitors, totaling nearly 1.5 miles, have been tallied on the peak, according to estimates cited by the park and Friends of Acadia.

Weber, a principal investigator in the restoration project, talked about the importance of saving Acadia plants.

“Species matter,” Weber said. “They just inherently matter.”

Despite all the inventory work done so far on Cadillac, new findings keep turning up, she said.

”We don’t understand yet all the relationships of all the species that are here,” she said.

The other principal investigator on the project is Bill Brumback, consultant and retired director of conservation for what is now known as the Native Plant Trust, formerly the New England Wild Flower Society. They are working in partnership with Acadia National Park, Schoodic Institute, and the Friends of Acadia.

Tests will determine best method for growing new plants

Atop Cadillac, the project is aimed at finding out what method would work best in restoring plants, while taking into account labor and costs. Experimental plots on the peak are surrounded by 40-to-50-pound sand bags to hold soil that the researchers have added to test plant growth.

The project follows an earlier attempt to revive plants on the Cadillac summit. For about 15 to 20 years, the park cordoned off portions of the peak and wanted to determine if plants could come back on their own, but progress was limited.

“There was some change, but it was too slow,” Weber said.

In 2015, the project began with a plant inventory on the 18-acre summit and collection of 20,000 seeds from 25 species, both common and rare, for restoration experiments, according to the Native Plant Trust.

The inventory found a tremendous diversity of Acadia plants with 145 species including five rare plants: Nantucket shadbush, mountain sandwort, mountain firmoss, boreal blueberry and Canada mountain ricegrass, the last found off the summit in a forest area.

Weber is one of the top experts on Acadia plants and their occurrences and descriptions. She is one of four co-authors of “The Plants of Acadia National Park,” teaches at the College of Atlantic and is holding a workshop on asters and goldenrods Sept. 6-8 at the Eagle Institute in Steuben.

Common plants on Cadillac summit include green alders

Weber said the effort on Cadillac is partly aimed at recreating many of the species associations that represent different types of vegetation on the summit including those of green alders, New York aster, balsam fir, black chokeberry, sheep laurel, low-bush blueberry, gray birch, goldenrod and three-toothed cinquefoil, which are little white flowers with 5 petals.

During the second year of the project, areas were picked for putting in plots for restoring plants, Weber said. Areas in four locations were set up on the summit with six different treatments and surrounded by ropes and sand bags.

One treatment is a control area where nothing is done. Weber and Brumback want to know what, if any, plants will establish in a spot that is left alone.

A second treatment uses coir, or coconut fiber, to try to keep the ground moist and catch some blowing seeds in the wild that might germinate without adding soil.

In a third treatment, seeds were sown on bare ground and topped with coir.

A fourth treatment included addition of some soil, or about an inch deep of Maine compost, is added to the coir with no seeds.

A fifth treatment includes coir, soil and seeds that are sown in the soil and allowed to grow.

In the sixth treatment, Weber and Brumback used exactly the same mix of seeds, but they first germinated them in a greenhouse and grew them for a couple of months in mesh-bottomed plastic flats before manually transplanting them at the summit in an area with coir and compost.

More soil spurs growth of Acadia plants

Weber said she is starting to get an idea of what works best.

Initially, the project used about an inch or so of soil and while it helped growth, the compost rotted and broke down quickly during the first winter. Starting in 2017, Weber said, five times as much soil was added.

“Adding soil made a difference and adding more soil made a bigger difference,” Weber said. “As long as you add soil, you get a lot more seedlings.”

Weber said the effort includes one more year of data collection and then the investigators will submit recommendations to the park and then park officials, including Rebecca Cole-Will, the park’s chief of resource management, and Nicholas Fisichelli, director of science and education for the park’s Schoodic Institute, will make a decision.

“The goal is to revegetate the summit,” Weber said. “Does one of these methods work best? The other question we have to answer is if a couple approaches work pretty well, is there is one that is more cost-effective?”

It can be a harsh environment for plants on Cadillac. The soil is naturally shallow with few deciduous plants, outside of the alders, to drop leaves that would decompose and create soil.

Anything that is growing is a survivor, and their resilience may hold some clues for the future, Weber said.

Cadillac summit free of invasive plants

The summit is also remarkably free of invasive plants. Weber said two occurrences of glossy buckthorn shrubs were found and removed.

In order to keep out invasive plants, Weber said, loam used on the summit was sterilized with special equipment to kill any seeds from weeds. The project uses the sterilized loam and a little peat moss to improve moisture and holding capacity.

Walking on the summit, Weber points out flat-topped white asters and the rare mountain firmoss.

“This is a nice clump of mountain firmoss here,” she said bending down to eye the progress. “They are not true mosses. They are low and they look kind of mossy, but they are more closely related to ferns.”

Brumback, a principal investigator on the project, has prepared some greenhouse-grown seedlings of the rare Nantucket shadbush, listed as a threatened species in Maine. Weber said they will be planting some Nantucket shadbush this year on the peak.

“The plant was thought to be endemic to, or grow only on Nantucket. When botanists conducted searches and research, they found that Acadia supports several different occurrences. I have collected seed from 10 to 12 individuals on the summit and that is our seed source.”

The prevalence of Nantucket shadbush surprised scientists and the study of botany is likely to unearth more revelations.

For example, botanists are only now starting to understand the connections among the below-ground relationships of plants, and the mutual links between a fungus and the roots of a plant and how that might increase a plant’s abilities to withstand certain environmental stresses.

“If we don’t preserve what is here, we will never know about those things, ever, because they will be gone by the time we have the technology to figure it out,” she said.

The bigger picture is that nature is critical for the well-being of people, she said. Nature and plants make people happy.

“Just being here is so therapeutic,” she said. “A bad day on Cadillac beats a good day in my office.”