a late afternoon in mid-december

Cold rain drizzles down, glazing everything in a silvery sheen. Around the neighborhood, along paths and sidewalks, winter berries glow in the gathering dusk: white globes of snowberries, holly berries bright as Christmas tree ornaments, mountain ash and cotoneaster berries in clusters of rust and orange. In our front yard, robins feast in the mountain ash tree, swallowing berries whole. Uneaten berries fall to carpet the garden and driveway, squishing underfoot when we go outside. Winter is a time to observe berries and think about their role in nature.

From a human perspective, berries are many things: beautiful garden ornaments; a source of juice, jam, or pie (in the case of edible berries); or food for wildlife. But what are berries for from the plant’s perspective?

what is a berry, anyway?

In simple terms, a berry is a package to hold seeds. This package protects the seeds from the elements and, by attracting animals to eat the fruit, it helps the seeds get spread across the landscape. All of this increases the chance that the plant will successfully reproduce and colonize new areas.

Seeds form when a flower is fertilized. The ovary of the flower surrounding the developing seed enlarges to form a fruit. Berries are one type of fruit — there are many others including drupes, nuts, samaras, achenes, and a host of additional fruit forms defined by botanists.

Salmonberry’s spring magenta flowers and summer fruit make it a favorite among humans and wildlife.

some berries in this region

The Salish Sea region has a host of native, berry-producing plants. Examples you might encounter on a walk through a low-elevation park or forest are snowberry, salal, salmonberry, trailing blackberry, dogwood, red and evergreen huckleberry, black raspberry, Oregon grape, serviceberry, black twinberry, coastal strawberry, elderberry, and thimbleberry. Some but not all of these are edible for humans.

People have introduced many nonnative berry producers to this region—from English holly and English ivy to cotoneaster, Himalayan blackberry, red raspberry, European mountain ash, coralberry, and a multitude of other agricultural and ornamental species.

Native dogwood has clusters of white flowers in summer followed by lovely white berries in winter.

Birds and other wildlife that consume berries play a major role in spreading plant seeds. You may have heard the explanation about why red huckleberries often grow from the tops of old stumps: Birds perch on the stumps, eating the berries and defecating the seeds. Red huckleberry favors rich, organic substrates to grow in, and rotting wood is perfect for this species. I don’t know whether the birds-on-stumps idea has ever been scientifically tested, but it sounds reasonable. Bird consumption of berries is also a reasonable explanation for how nonnative plants such as English holly seem to suddenly spring up within forests; presumably a bird ate some holly berries in a neighbor’s yard before it flew into the forest where it defecated the seeds.

native and non-native

I’ve often wondered whether the spread of non-native plants has impacted the ability of native berry-producing plants to attract wildlife (and thus spread their seeds). For example, if birds are gorging on the berries at my nonnative mountain ash tree, does this mean they are eating fewer berries from native plants elsewhere in the neighborhood? As with everything in ecology, the answer is complicated and as yet largely unknown.

Some studies have found that native berries are preferred by birds even when nonnative berries are also present; other studies have not supported this idea. Several articles I read stated that native berries are generally more nutritious and especially important for birds getting ready for migration. With climate change, the timing of bird migrations and the peak fruiting times of native plants appear to be changing, meaning that birds may miss the best of the native berries on their travels.

There’s a lot of current research into whether our traditional ideas of “good” (meaning native) and “bad” (meaning nonnative) species still holds up in a world so deeply modified by humans. One idea is that an abundance of berries attracts birds, whether the berries are native or not. Having nonnative berries around to “bulk up” the total quantity of berries in an area may bring in more birds to eat (and disperse the seeds of) native plants. Providing ornamental berry species may also fill a food gap during seasons or situations where native berries aren’t available. The abundance of mountain ash, holly, and other ornamental berries around my neighborhood may make it easier for species such as robins to hang around during the winter. People have created an abundant year-round food source for some wildlife species.

Salal flowers. photo by John F. Williams

it’s complicated

But berries don’t tell the whole story of how nonnative plant species affect wildlife and ecosystems. Many birds and other wildlife eat a variety of foods throughout the year, including both fruits and insects. Some birds specialize as insect eaters. Research has shown that some popular ornamental plants support very few of the insects that native birds evolved with and rely on as a seasonal food source. A new concept is the idea of “keystone plant species,” meaning plants that provide the best habitat for insects, particularly caterpillars.

Coralberry glazed in a winter ice storm, a nonnative species related to our native snowberry.

Sara Noland grew up in the wilds outside Renton, attended UW and Western, and has lived in Everett for the past quarter century. She was fortunate to spend a quarter of her undergraduate life at UW Friday Harbor Laboratories. She shares a tiny house with her husband and a herd of cats and dogs. Sara works and volunteers as a biologist and writer; her favorite topics are Washington beaches and lowland forests.

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Thanks so much for your interest and your support.