Scientists agree: Global warming is real, and it’s happening today. Here in northeast Ohio, we can most clearly see the signs during spells of too-warm-too-early weather in the spring or in stronger-than-average storm fronts. The plants feel it, too—plants depend on temperature cues for the progression of their annual life cycles. But not all plants respond the same way when their environment gets shaken up. Ecologists have noticed that nonnative plants, that is, foreign-origin species that have established here, sometimes seem to be able to shift their life cycles more easily than natives. If true, this could give these exotic species an edge over natives, which could in turn worsen the extent and impact of invasive species in our ecosystems.

Here in our biome, the eastern deciduous forest, you can see this phenomenon most clearly in early spring and late fall, when many of the still-green plants you see are nonnative species like multiflora rose or glossy buckthorn— these species often have extended growing seasons compared to native plants. At these times, the Ohio-native plants have gone to sleep (or not yet woken up) for the season—but imported species like lawn grasses and invasive forest shrubs are still green and soaking up the sunshine.

A research team based out of the Holden Arboretum recently synthesized decades of scientific research to better understand how, exactly, exotic plants shift their life cycles under rising temperatures—and what the consequences might be for ecosystems. They published their report in the journal Annals of Botany. 

What will happen when the planet gets warmer?

Phenology—the timing of seasonal events like leaf-out, flowering, and fruiting—is one of the most well-documented ways that climate change is affecting plant life. There’s already clear evidence that warming impacts phenology in all sorts of different ways, since so many plants depend on temperature cues.

How long a plant spends in each life stage and when it moves on to the next can have big impacts on its health. For instance, imagine a flower that opens at the wrong time or doesn’t stay open long enough to allow any pollinators to stop by—that could be enough to prevent it from reproducing. 

Ecologists have long suspected that nonnative plants will be more responsive to warming than native plants. But when you look at the research on the subject, results are mixed. That’s why the Holden team embarked on this study to figure out what the research, on the whole, has to say about exotic plants and climate change. 

The researchers did a deep dive, screening thousands of papers and conducting an in-depth review of 54 of the most relevant ones. The work was co-led by Emma Dawson-Glass and Rory Schiafo, two former research specialists in the Stuble lab. Dawson-Glass and Schiafo are both now graduate researchers at the University of Michigan and Northwestern University, respectively.

Results Are In

The team found the most consistent timing shifts were those earlier in the season, like spring leaf-out and flowering. Both native and nonnative plants shift their timing earlier with warming, but there was also consistent evidence that exotic species advance more than natives, potentially giving invasive species a competitive edge.

Life stages that occur later in the season, like fruiting or die back, were less consistently affected. Some species moved through their life stages faster in response to warming, while others remained unchanged or progressed more slowly.

Why the inconsistencies? The researchers looked into that, too, and found a few patterns related to which nonnative species responded in different ways to warming. They learned that  a species’ evolutionary history, its geographic origin, and the environmental conditions of their invaded habitats all gave clues to how the plant will respond to warming.

Ecosystem Impact

The ecological consequences of both global warming and exotic species invasions are complex enough on their own—they’re even more complicated when occurring together. Research is starting to reveal the ways in which changes to plant phenology can cascade through ecosystems. It can affect species interactions, for instance tipping the balance in favor of nonnative species as they compete with natives for space and resources. It could even influence large-scale processes, like the carbon cycle.

“Our review underscores that while nonnative plants often shift their phenology in response to climate change, the patterns can differ depending on features about each plant and the ecosystem it’s invading,” says Dawson-Glass. “Understanding these nuances will be essential for conservation efforts, as well as for predicting which species might become more dominant under future climate scenarios.”

Katie Stuble, senior author and Director of Research at HF&G, emphasized the importance of continued study in this area. “This work highlights the need for more research, particularly in underrepresented regions and ecosystems. The more we understand about these shifts, the better we can anticipate and mitigate potential ecological disruptions.”

This study provides a roadmap for future research, calling for broader studies on nonnative plant phenology across different ecosystems and climatic zones. By expanding the scope of research, scientists will be better equipped to develop strategies that support biodiversity and ecosystem stability in the face of a changing climate.

Photo: Early spring at HF&G.

Citation: Dawson-Glass, Emma, et al. 2025. Toward a comprehensive understanding of the phenological responses of nonnative plants to climate warming: A review. Annals of Botany, mcaf008, https://doi.org/10.1093/aob/mcaf008

About Holden Forests & Gardens: Holden Forests & Gardens is made up of two of Northeast Ohio’s most important environmental and cultural institutions—the Holden Arboretum and Cleveland Botanical Garden—whose mission is to connect people with the wonder, beauty, and value of trees and plants, to inspire action for healthy communities. One of the largest public gardens in the country, Holden Forests & Gardens has 21,000 member households and an annual attendance of nearly 350,000 for whom we strive to provide inspirational and educational visitor experiences. For more information, visit holdenfg.org.

Corresponding Author:
Dr. Katie Stuble, Research Chair
Holden Forests & Gardens
[email protected]

Media Contact:
Dr. Anna Funk, Science Communications Specialist
Holden Forests & Gardens
[email protected]