Why native plants matter, and how to choose the right ones

Native is about relationships, not looks

Belonging takes a long time to earn. The plants that grew up alongside your local insects over thousands of years are, very often, the only ones those insects can eat.

That isn't a figure of speech. A global study of plant-eating insects led by Matthew Forister, published in PNAS in 2015, found that 76% of the species sampled fed on plants from just one plant family. A 2018 paper by Desirée Narango and colleagues puts it more broadly: over 90% of plant-eating insects specialize on one or a few native plant lineages. Swap the plants and those insects have nothing to eat.

Birds run on caterpillars

Most songbirds can't raise a family on seeds. A review in the journal HortTechnology, drawing on earlier work, reports that 96% of North American land birds feed insects to their young. Caterpillars are the staple: Audubon reports it can take 6,000 to 9,000 of them to raise one brood of chickadees.

Narango's team followed Carolina chickadees nesting in residential yards. Where non-native plants dominated, there were fewer insects, and the chickadees raised fewer young or skipped breeding. Their study found that yards needed more than 70% native plants by mass for the population to sustain itself. Yards below that line acted as population sinks.

A few plants do most of the work

You don't need hundreds of species to make a difference. In a 2020 study in Nature Communications covering 83 U.S. counties, Narango, Douglas Tallamy, and Kimberley Shropshire found that on average just 14% of local plant genera supported more than 90% of butterfly and moth species. They call these keystone plants.

The top woody keystones in their data were oaks, willows, cherries and plums, pines, and poplars. Landscapes missing these genera supported, on average, about half as many species of butterflies and moths. If you plant one tree, a locally native oak is hard to beat.

Bees, butterflies, and the milkweed question

North America has about 3,600 native bee species, according to the Xerces Society, and roughly 70% of them nest in the ground, so a few undisturbed patches of bare soil help. Xerces notes that bees tend to prefer native plants, which are also adapted to local climate and soil.

Monarch caterpillars eat only milkweed, as the U.S. Forest Service explains. But plant the right one. Xerces recommends milkweeds that are native to your area and advises against tropical milkweed, which can keep its leaves year-round in mild climates and may raise the rate of a parasite that infects monarchs. There are more than 70 milkweed species native to the United States, so there is almost always a local one.

How to choose the right plants

"Native" is local, not national. A plant native to Arizona is not native to Ohio. The EPA maps the country into ecoregions, areas where geology, soils, climate, plants, and water are broadly similar, with 105 of them in the lower 48 states. That's a better starting point than a state line.

Then match the plant to the spot. A federal introduction to native plant restoration warns that moving a plant population to a place with different freezing or moisture conditions can mean poor growth or death. Sun, soil moisture, and space still decide what will thrive.

• Search by state, light, and soil moisture in the Lady Bird Johnson Wildflower Center's native plant database.
• Buy from local native plant nurseries when you can, especially near natural areas, where locally grown stock matters most.
• Be thoughtful about cultivars. A 2018 study by Baisden and colleagues found that cultivars bred for red, blue, or purple leaves discouraged insect feeding, while other traits showed no consistent effect. Green-leaved forms close to the wild plant are the safer bet.

Invasive plants: remove, then replant

Federal policy defines an invasive species as a non-native species whose introduction causes, or is likely to cause, economic or environmental harm or harm to human health. Familiar examples include Callery pear, English ivy, autumn olive, Japanese honeysuckle, Japanese barberry, and multiflora rose.

Pulling them out is only half the job. University of Maryland Extension advises replanting with natives as soon as possible, because cleared ground is easily taken over again, and then keeping an eye out for regrowth. Check your state department of agriculture or invasive species council for the list that applies where you live.

Roots, soil, and water

Native grasslands are also built for water. Iowa State University notes that prairie soils can hold more than 10 tons of roots per acre, mostly in a dense mat in the top foot, with some roots reaching past 8 feet. Those roots and the organic matter they leave behind help the soil act like a sponge.

On farms the effect can be striking. Iowa State's STRIPS research reports that converting 10% of a crop field to strips of native prairie cut sediment loss by 95%.

What to expect

Native doesn't mean no work. The same federal guide notes that natives need the same care during planting and establishment as any other plant. Purdue University's Landscape Report calls native gardens low-maintenance, not no-maintenance, and names weeding as the task people most underestimate.

Expect a slow start. Purdue describes the familiar pattern as sleep, creep, leap: little visible growth the first year, more the second, and a planting that fills in by the third. Give it that time and it starts to feed the web around it.