Naturalizing has two common meanings depending on context. In ecology, it describes the process by which a non-native species establishes itself in a new environment, surviving and reproducing without human help. In gardening, it refers to planting flowers or bulbs so they spread on their own and create a wild, informal look over time. Both meanings share the same core idea: something becomes self-sustaining in a place where it didn’t originally exist.
Naturalizing in Ecology
When ecologists say a species has “naturalized,” they mean it was introduced to a new region (deliberately or accidentally) and now survives and reproduces in the wild without cultivation or ongoing introductions. This is a specific stage in the invasion process. Most introduced species fail to establish themselves at all. Of those that do take hold, only a fraction naturalize, and only a subset of those go on to become invasive by spreading over large distances and forming huge populations.
The distinction matters. A naturalized species is reproducing on its own but may remain relatively stable in its range. An invasive species is actively expanding, often with measurable environmental or economic damage. The USDA defines an introduced plant as one that reproduces spontaneously in the wild without human help and tends to persist. Plants that show up briefly but don’t stick around are classified as “waifs,” a category below true naturalization.
The scale of naturalization worldwide is enormous. A major global dataset now tracks over 39,700 alien species across 289 regions, covering plants, animals, fungi, and microorganisms. Plants make up the largest share. On islands, thousands of exotic plant species have naturalized while relatively few native plants have gone extinct, meaning total plant richness has climbed dramatically. For birds, the pattern is different: the number of naturalized exotic birds on oceanic islands has roughly matched the number of native bird extinctions, keeping overall species counts stable but replacing unique endemic species with common ones found on mainlands.
What Determines Whether a Species Naturalizes
Not every introduced species can make the jump. Research on ornamental plants sold in 19th-century Quebec found that cold hardiness was the single strongest predictor of whether a plant would naturalize. Species that could tolerate the local winter survived long enough to reproduce without gardeners replanting them each year.
Becoming invasive requires an additional set of traits beyond just surviving. Lighter seeds, multiple dispersal methods (especially by water), and vine-like growth habits all increase the odds that a naturalized species will spread aggressively. Plants originating from temperate Asia or Europe were particularly likely to become invasive in Quebec’s climate, likely because those regions have similar growing conditions.
How Naturalized Species Affect Native Ecosystems
The ecological impact depends heavily on the type of organism. Predation by exotic animals has caused many native animal extinctions on islands, but competition from exotic plants has caused surprisingly few native plant extinctions. Plants seem to coexist more readily, at least in the short term. On Lord Howe Island, for example, only 4 of 183 naturalized plant species have been lost over time, and previously established naturalized plants don’t appear to get pushed out by newer arrivals.
That said, the lack of outright extinction doesn’t mean everything is fine. When naturalized species replace endemic ones, biological communities become more homogeneous. Islands around the world increasingly share the same pool of cosmopolitan species rather than hosting the unique lineages that evolved in isolation. This loss of distinctiveness is a major conservation concern even when raw species counts hold steady.
Naturalizing in Gardening
In horticulture, naturalizing means planting bulbs or perennials that multiply on their own year after year, creating a look that mimics a wildflower meadow rather than a formal garden bed. The key is choosing species that spread easily without replanting. Once established, a naturalized planting gets bigger and more impressive each season with minimal intervention.
Bulb lawns are one of the most popular ways to naturalize a yard. The technique is straightforward: mow the turf short, mark off the planting area, and use a bulb auger on a drill to make holes quickly. Drop a small amount of organic bulb fertilizer and a few bulbs into each hole, backfill with the displaced soil, and optionally overseed with rye grass to hide the disturbance. The goal is a scattered, informal arrangement rather than neat rows.
Best Bulbs for Naturalizing
The strongest approach uses several species with overlapping bloom times so color appears from late winter through fall. Early bloomers include snowdrops, winter aconites, crocus, and dwarf irises. Midspring brings woodland tulips, miniature daffodils, glory-of-the-snow, Siberian squill, and grape hyacinths. Various allium varieties can bloom from early spring well into fall and are particularly attractive to pollinators. Lilies, from straight species to oriental varieties, flower at different times, making them useful for extending the display even further.
Pest resistance matters when choosing bulbs. Deer love tulips and will eat crocus, but most other naturalizing bulbs are unappealing to deer and rodents. Daffodils are especially effective as a deterrent, so interplanting them with more vulnerable species offers some protection. For pollinator support, single-flowered varieties are best because their nectaries are easier for insects to access than double-flowered cultivars.
Why Naturalized Gardens Help Pollinators
Naturalized plantings do more than look good. Research on conservation-oriented gardening shows that the features of a garden may influence pollinator diversity more strongly than the surrounding landscape, giving even small yards real ecological value. Plants suited to naturalized gardens tend to prefer nutrient-poor soils (25% of conservation gardening species versus just 7% of conventional ones), which means less fertilizer and lower maintenance. They also handle drought better: roughly 45% of these species prefer dry soils, compared to 27% of conventional garden plants. In a warming climate with longer dry spells, that resilience translates to less watering and lower costs for the gardener.
Naturalizing in Social Science
In psychology and philosophy, naturalizing refers to the process by which something socially constructed comes to be seen as natural or inevitable. Gender roles are a common example: behaviors shaped by culture get treated as though they are hardwired into biology. This “kind constructionist” view holds that human traits and categories are produced by culture rather than by innate biological states, and that the boundary between what counts as natural versus constructed has real consequences for how societies organize themselves and treat different groups of people.
The concept also appears in philosophy of science, where it describes the tendency for dominant theories to shape what observers notice and report about the physical world. Background assumptions about difference or sameness can influence perception so strongly that observational data becomes compromised as an independent check on those same assumptions.