Athletes, Survivalists and Opportunists in Your Garden

Understanding the plants we share our planet with is a key mission of botanic gardens worldwide. Denver Botanic Gardens delivers on this goal through collaborative research with universities and other organizations. This summer, on behalf of the Norwegian University of Life Sciences, I had the privilege of joining a two-month research exchange with the Gardens' horticulture research team. I'm Alex, and I will share some insights from our work together.
Recently, there's been a growing focus on choosing plants that thrive in their environments—not just survive. Ecology offers us a powerful tool for making smarter planting decisions: the CSR theory. Don't let the acronym put you off—it simply stands for Competitor, Stress-tolerator and Ruderal, representing three fundamental survival strategies plants have evolved over millions of years.

British ecologist Phil Grime pioneered this theory, showing how three environmental forces shape plant evolution: competition, stress and disturbance. These forces act as selective pressures, selecting for species with certain physiological and morphological traits. 

Competitors

Competitors are the athletes of the plant world. They excel where resources are plentiful, growing fast and tall to outcompete their neighbors for light and space. Picture that vigorous vine taking over your fence—classic competitor behavior.

Stress-tolerators

Stress-tolerators are the survivalists. They thrive where others can't—in poor soils, drought conditions or extreme temperatures. These plants are conservative with their resources, like cacti hoarding water in the desert.

Ruderals 

Ruderals are the opportunists. They quickly colonize disturbed areas like construction sites or a freshly tilled garden bed. They grow fast, reproduce early and die young—nature's entrepreneurs.

Many plants fall somewhere between these extremes, adapting to intermediate conditions without specializing in any single strategy.

So how do we figure out a plant's strategy? The answer can be found in their leaves. By measuring specific leaf characteristics—thickness, area, dry matter content—we can accurately predict where a plant falls on the CSR spectrum. That's exactly what we've been doing with some of the Gardens' most promising herbaceous species.

We plot these measurements on a triangular graph, with each corner representing one strategy. A plant's position reveals its survival tactics and, more importantly, which habitat it will be best suited to.

This knowledge informs how we design gardens and green infrastructure. Competitive species flourish in rich, moister locations but might need regular management to prevent spreading. Stress-tolerators are perfect for that impossible dry slope or roof garden. Ruderals work well in frequently disturbed areas but remember—they're short-lived and will self-seed enthusiastically, which can be either a blessing or a curse depending on your goals.

Next time you visit Denver Botanic Gardens, try looking at the plants with this in mind. That tough little alpine isn't just surviving—it's executing a million-year-old strategy perfected for harsh conditions. Accurately visualizing such strategies helps us work with nature rather than against it, creating more ecologically robust landscapes.

This article was contributed by Alex Clarke, Ph.D. researcher, The Norwegian University of Life Sciences.