There's a quiet drama playing out on the grounds of Princeton University. In recent years, the University has been making a shift to landscaping with native plants. Homeowners, too, are being encouraged to go this route, so it can be instructive to take a look at how the University is doing. Despite all of its resources, the University struggles like the rest of us. Anyone can mow a lawn, but a complex native planting requires expertise to maintain. It takes skill, strategy and understanding to work with nature, rather than simply suppress it with a mower.
This post documents some ways the University is making native plantings easier to maintain, but points out the risks, past and present, of not investing adequately in maintenance. It also describes how early, strategic intervention can steadily reduce maintenance needs, and tame the tiger of weeds.
First, a review of the University's successes and failures over the years.
One success thus far is the Betsy Stockton meadow, dedicated in 2018 atop the underground portion of the Firestone Library. A profile of the meadow that I wrote in 2024 mentions some weedy crown vetch beginning to spread through the beds, but it looks like the caretakers have since intervened.
A native meadow planting at the Butler Tract in 2016 suffered a similar fate.
In more recent plantings, the University has adopted a couple strategies to avoid losing out to weeds. One is to plant dense stands of natives.
Here's a dense stand of white snakeroot ornamenting Whitman College in early October.
A more complex native planting with multiiple species near Myslic Stadium is doing well.
It's fun for a botanist to stroll up to a soccer game along a pathway bordered by side oats grama, a grass common in the Great Plains.
Other newer plantings that looked great for a couple years are now struggling as weeds have moved in. This impressive stand of native cutleaf coneflowers along Fitzrandolph Road is besieged by foxtail, crabgrass, and other typical weeds. You can see where glyphosate was sprayed along the edge as a preliminary step, but the weeds were left to go to seed in late August.
By chance, one of my visits to the campus plantings coincided with a work crew immersed in weeding the beds across the street. The piles of weeds on the walkway attest to how much work needed to be done.
Before hauling away a bucket full of weeds, the supervisor told me a few things about maintaining the new native plantings. He was frank about the situation. The work in the heat of late summer is hard on his crews, and it seems they had to hire outside workers to augment staff.
Here is a freshly weeded bed, demonstrating a second approach to sustaining native plantings. Rather than planting densely, space was left between desired plants so that any weeds growing inbetween could either be pulled or spot sprayed.
To take just one example, while checking out one of the newer University plantings, I found one plant of stiltgrass. Elsewhere in Princeton, you might find billions of stiltgrass plants smothering the landscape, but here on campus there was only one to be found in a large native planting. I pulled that one stiltgrass before it could produce seeds, thus liberating the whole planting from this one incredibly aggressive weed. Gardening is much easier if you know what to look for and catch it early.
The vast majority of the university grounds is free of stiltgrass, and could potentially be kept that way, but I did find this one patch, growing just north of the New South building. Since the seeds get carried downhill by runoff, I "followed the water" and found where it had spread to create another patch just down and across the road.
The patch further down, though, near Baker Rink, was left to go to seed. This infestation, which ultimately threatens a broad swath of campus, is still at an early stage where it could easily be knocked out proactively--an hour devoted each year to spraying it with super-dilute, low toxicity herbicide before it goes to seed, until the soil's seedbank of this pernicious weed is exhausted.
Here's partridge pea planted thickly. A nitrogen-fixing legume with graceful leaves and long-lasting blooms, partridge pea has a lot to like.
And here's river oats, another native effective at forming dense stands. Personally, I don't plant river oats because it seeds into areas where I don't want it, but it makes sense for a dense planting on a university grounds.
Switchgrass, a native tallgrass prairie species, grows thick near the soccer fields. Planting a solid stand of one species requires less knowledge to maintain, since the staff can be told to weed out any plant that looks different, like the nonnative giant foxtail in there that could cause problems over time.
He said the weeds they remove are then composted and added to mulch that they then spread on the beds. If the composting process isn't hot enough to kill the weed seeds, they are then applying mulch that will sprout weeds.
I followed up with the grounds department, sending an email suggesting they use woodchip mulch that lacks weedseeds, perhaps getting some from the municipal composting site nearby.
If there's one thing I've learned from all my years of gardening and land management, it's to stay ahead of the weed seeds. Garlic mustard, pilewort, stiltgrass, giant foxtail--we pull them all at Herrontown Woods before they can produce zillions of seeds that would otherwise create extra work for years to come. It goes against human nature, and it goes against bureaucratic logic, which wants to do things on its own schedule. No, one has to keep an eye on the weeds, react to their schedule, not one's own, and intervene before they form seed.
I sent an email to the facilities staff in late August, before the stiltgrass began to go to seed, encouraging them to intervene. A followup visit in early October found they had at least mowed the first infestation.
There's a philosophy, a strategy for success, embedded in all of this observation and advocacy. Some forty years ago, I had a powerful dream in which I was riding in an open car down a street near my house. I saw a large tiger ahead, resting on the ground. As we approached, my worst fears were realized. The tiger rose and jumped up upon me. As I tumbled with it out of the car and onto the ground, the fierce tiger became a kitten, with me bent over it, tickling its belly. Caring for a native planting can feel like that dream. Pull the weeds before they go to seed, and over time the weeds grow few while intended plants grow dominant. Weeding becomes light work. Toil becomes ease and enjoyment. The intimidating tiger turns into a gentle kitten.
That is what I wish for Princeton University's grounds. Aim for a zero tolerance approach to weed seeds, moving each year closer to a weed-free campus, with each year of tending native plantings easier than the year before. Let the tigers roar in the stadiums, but tame them in the garden beds.
Related reading:
A good article in the Princeton Alumni Weekly: Princeton Landscaping Goes Back to the Wild With Native Plants
