Why are my strawberries small or deformed?

Pick a few misshapen berries and look closely at the seeds on the outside. On fruit damaged by tarnished plant bugs, the seeds are uniform in size, often tan and hollow, and the tip of the berry is hard and seedy — sometimes called a button berry. On poorly pollinated fruit, the seeds vary in size across the berry. Then look at the whole flower cluster. University of Maryland Extension notes that frost tends to deform the first, largest berries and leave later ones normal, so good and bad fruit share a cluster, while plant bugs usually damage the entire cluster.

Tarnished plant bugs are a common cause. They are fast-moving, mottled brown bugs about 1/4 inch long with a pale yellow triangle on the back; the young nymphs look like green aphids that run. Both feed on the developing seeds, and the berry stops growing in the area around each damaged seed, leaving it small, knobby or lopsided. NC State Extension notes that nymphs feeding at or before petal fall cause the worst deformities. Check plants during bloom by tapping flower clusters over a white tray.

Poor pollination comes next. A strawberry swells around its pollinated seeds, so a berry with few pollinated seeds stays small or forms unevenly. University of Maryland Extension notes that fully pollinated flowers produce the largest, best-shaped fruit, and lists too few bee visits and frost on early flowers as causes of misshapen berries. Cool, rainy weather during bloom keeps bees grounded, which is why the first picking is often the worst. A frost during bloom can kill the center of a flower, which may turn black, or damage only part of it so the berry forms lopsided.

Small but normally shaped berries have different causes. The first berries are the largest, and each later set of berries is smaller, so small fruit near the end of the harvest is normal. A bed that has filled in with runners is the other common reason. Crowded plants compete for water, light and nutrients, and University of Maryland notes June-bearing beds typically decline after 3 to 4 years from crowding and disease. Strawberries are shallow-rooted, so dry spells while the fruit sizes up show quickly.

Remove deformed fruit as you find it; it is fine to eat if it isn't rotting. After a June-bearing bed finishes fruiting, renovate it: mow or cut plants to 2 to 3 inches, above the crowns, thin daughter plants to 6 inches apart, and narrow the bed to 12 to 18 inches wide. In spring, pull or mow flowering weeds near the bed, since plant bugs build up on them. Insecticidal soap or neem oil can reduce nymphs; spray in the evening, keep it off open flowers, and don't spray above 90°F. Row covers on frosty nights protect blossoms.

Before using any product, read the whole label. It must list the crop you’re treating, and its directions on amount, timing, protective gear, bees and days before harvest are legal requirements. If this page and the label disagree, follow the label.