If you visited the Pollinator and Bird Garden this year, you were probably struck by the transformation. Last year’s garden was lush. This year, there are patches of bare earth.
Anyone who has ever planted a garden will recognize the problem: some plants were doing too well and needed to be removed or edited out to make room for less aggressive species.
Two of the most troublesome overachievers were uninvited guests: mugwort (Artemisia vulgaris) and Canada thistle (Cirsium arvense). These common, hard-to-control invasive species arrived as seeds hidden in a load of soil when the garden was being built. Once established, they began to swallow the deliberate, research-critical species that were intended for the garden.
The Pollinator and Bird Garden’s core design relies on plants forming a living tapestry, with high-performing native species filling every ecological niche and outcompeting the weeds. In some areas, the high performers were too successful. When conditions are favorable, some desirable native plants can turn into aggressive “garden bullies” and overwhelm their slower-growing neighbors. Mountain mint (Pycnathemum virginianum), Canada anemone (Anemone canadensis), cup plant (Silphium perfoliatum), and goldenrods (Solidago spp.) are examples of native plants that were doing so well that they were starting to take over, forming dense single-species patches. The anemone may have been humming with bees, but it was also invading nearby garden beds and outcompeting other plants.
How do you recalibrate the balance of a garden that is being threatened by a wave of invasive weeds and aggressive native plants? Our first, fundamental realization was that managing a landscape as dynamic as the Pollinator and Bird Garden invites burnout. Sustaining the garden means sustaining our horticulturists, so we created new support positions and brought Penn State researchers, landscape designers, and outside experts to the planning process. Together, this committee decided on a comprehensive rebalancing strategy that combines wholesale elimination and precision editing.
The goal wasn’t tidiness, with individual plants specimens nestled in a sea of mulch. It was optimization of a complex plant community, backed by science-informed design and operational reality. We used real data and experience to focus on what works, so we can let go of what doesn’t.
Arboretum horticulturists destroyed weed colonies and removed patches of native species that had become overenthusiastic where they were planted. Hand-pulling individual plants was not enough to restore these hard-hit garden zones; only a complete reset could interrupt the rain of seed into the soil and give desirable species a chance to establish themselves.
Weed eradication is the sledgehammer of garden maintenance, resulting in unlovely stretches of bare earth. Where possible, horticulturists adopted a more delicate surgical technique, thinning out aggressive native species to give their weaker neighbors room to thrive. This precise editing isn’t as jarringly visible as the elimination of a weed colony, but in time, both approaches will yield the same result: a more diverse and interesting landscape.
Subtle adjustments to the garden design will make future maintenance easier. The redesigned Pollinator Border near the bee hotels incorporates maintenance paths to make it easier for horticulturists to attend to dense plantings and trim trees and shrubs. Over-vigorous shrubs may be replaced with slower-growing or more compact varieties. The re-designed border will be optimized for our gardeners, and feel familiar to our guests, serving as a source of inspiration.
Nothing makes bare earth look like anything other than a weed-control zone, but the Pollinator and Bird Garden provides an object lesson about how good “bones” will keep a garden looking tidy during the rebalancing process. Strong architectural anchors like the Pollinator Disc and birdhouse provide focal points in the landscape, and mowed edges and clean paths signal that this is a garden, not a field. A garden undergoing an intensive maintenance phase, but a garden nonetheless.
If there is one message about the Pollinator and Bird Garden today, it is that a garden is always a work in progress. Each season shifts the ecological balance: factors like moisture, heat, weeds, and pests all rise and fall in importance. Species that do well one year may struggle the next. Our role is not to freeze the garden in time but to guide it through these changes so that it remains what it was intended to be: a designed echo of a wild, resilient landscape, backed up by science and operational reality. So far, the strategy is holding, and with continued editing, we think that we will maintain a steady course. Watch this space!
Looking for lessons for your home garden? Here are some things we have learned:
- Know your weeds. That will help you determine the right control strategy.
- Map your landscape. One of our first steps was to create extensive weed maps to help us target the hardest-hit areas and identify developing trouble spots.
- Make space for maintenance. Build access paths through or behind dense plantings so you won’t need to wade through your plants to weed and trim them.
- You’re only human. Some garden projects require more help: in our case, we needed more staff and to bring back our team of designers, scientists, and outside experts!
- Editing is easier when plant clumps are bigger. Plant multiple individuals of the same species in a block to make it easier to identify weed infiltration. Big plant masses also look more appealing to humans—and attract more pollinators!
- Don’t get too attached. A beautiful plant that is acting as a garden bully can be replaced by a beautiful plant that works better in the landscape. Similarly, a beautiful plant that is too short-lived or slow-growing for a space can be replaced with something hardier.
- Stay true to the story of your garden. In the Pollinator and Bird Garden, our goal was a sustainable landscape that provides maximum habitat, with waves of blooms from spring to fall. When we had to make the hard choice to edit out an underachieving plant, we replaced it with a species that will perform a similar function.