Strawberries

Every strawberry question you’ve ever had – answered!

A Q&A with Lisa Wasko DeVetter, Washington State University – Small Fruit Horticulture

VF: What type of strawberries are most commonly grown in Western WA? 

LWD: Growers commonly cultivate June‑bearing strawberries, day‑neutral strawberries, or a combination of both. June‑bearing cultivars produce a short but concentrated harvest period and are known for excellent fruit quality in western Washington. The strawberry season can be extended, however, by pairing these short‑fruiting June‑bearers with day‑neutral cultivars. Day‑neutrals continue to flower and fruit throughout the summer and into early fall until frost or heavy autumn rains bring the season to a close. This combination allows growers to offer high‑quality fruit over a much longer harvest window. 

VF: What’s the difference between ever-bearing and June-bearing? 

LWD: Strawberries are categorized by how they respond to day length, which determines when they form flower buds and produce fruit. I, along with many Pacific Northwest colleagues, recognize three main types. The first are June‑bearing strawberries, which are short‑day plants that form flower buds in the crown of the plant during late summer and fall and produce a single, concentrated harvest from late May through June the following year. Everbearing strawberries are long‑day plants that form flower buds during summer and early fall, resulting in a fall crop and sometimes a smaller spring crop. A third type, day‑neutral strawberries, is less influenced by day length and instead responds to temperature, generally flowering and fruiting whenever conditions remain between about 40 and 90 °F. Understanding these differences helps growers select the right mix of cultivars to achieve their desired harvest window. Of these three types, June-bearing and day-neutral strawberries are most common. 

VF: Why do regional farmers work with starts instead of seed? 

LWD: Strawberries are grown around the world, which means different regions need plants at different times of the year. This creates steady demand for nurseries that produce strawberry plants and the type of planting material available varies throughout the year. In the Pacific Northwest, commercial growers typically plant dormant, bare‑root plants in spring that were dug the previous year and frozen in California before being shipped north. Home gardeners, in contrast, often purchase plants from a wider range of suppliers and can access non‑dormant plugs produced through tissue culture. Growing strawberries from seed is an emerging practice in some parts of the world, but the seed must come from true‑breeding lines in order for the resulting seedlings to be genetically uniform. True‑breeding lines are currently rare in North America, and when they are not used, seedlings will be genetically diverse and will not grow true-to-type for the named variety.

VF: Do the farmers have to use plastic? What happens to plastic after the season? 

LWD: Day‑neutral strawberries are cultivated differently than June‑bearers and are often grown on black plastic mulch in cooler regions such as western Washington. This is partly because runner formation is not needed when producing day‑neutral strawberries, while runners are essential for establishing June‑bearers in the Pacific Northwest. Runners are above‑ground stems that form clonal daughter plants that need to root in soil and create the contiguous matted row typical of June‑bearing systems. In contrast, day‑neutrals produce few runners and are grown as individual plants rather than as a continuous row. Because runner formation is not required, growers can take advantage of plastic mulch, which suppresses weeds, conserves soil moisture, and increases soil temperature. Most plastic mulch is currently landfilled, but efforts to recycle it are increasing and growers are also being encouraged to consider soil‑biodegradable mulch alternatives.  

VF: What’s the best way to overwinter strawberry plants? 

LWD: Winters in the western Pacific Northwest are generally mild, and winter damage to strawberries is infrequent. Before overwintering, June‑bearers should be renovated shortly after harvest by mowing back the foliage, applying fertilizer, and allowing runners to re‑establish from late summer into fall. After renovation, the plants can overwinter without additional intervention, although growers should continue to manage weeds because winter weeds can become problematic. Day‑neutrals are often grown as annuals, but they can be overwintered for two to three years before production declines. To do this, reduce nitrogen in early September and remove or mow back foliage during winter so new growth can emerge in spring. In most cases, no straw or other overwintering material is needed for either type, but if a late winter or spring frost is expected, floating row covers or frost cloth can be used to protect frost‑tender flowers.

VF: What is your lab currently working on regarding local berries? 

LWD: Our lab works across blueberry, raspberry, blackberry, and strawberry systems, and we collaborate closely with raspberry breeding, entomology, and plant pathology colleagues within and outside of Washington State University. Characterizing and mitigating heat and cold stress is a major focus of our work in blueberry, blackberry, and raspberry. We also evaluate alternatives to black plastic mulch in strawberry production, including recycling programs and soil‑biodegradable mulch options. In the coming year, we will begin two new projects that explore machine harvesting technologies for fresh‑market blueberry and investigate the factors that influence raspberry fruit integrity. None of this would be possible without the many dedicated students, postdoctoral researchers, and technical staff who make our work successful.

Thank you Lisa & WSU Small Fruit Horticulture program!