Although the harvest of strawberries, raspberries, blackberries and blueberries is over for the season, continued care of your berry patch through the fall and winter will minimize plant loss and ensure a good harvest next year.
After temperatures have dropped below freezing, apply 3-5 inches of organic mulch such as straw or pine needles on top of your strawberry planting. If you apply mulch before the first frost, you will create artificially warm conditions, and your strawberry plants might start growing instead of going dormant.
As cold temperatures set in, watch for frost heaving. If strawberry plants are pushed out of the ground, replant them so that their roots are completely covered with soil.
In spring, remove the mulch when your strawberries show signs of growth such as new leaf emergence. If frost threatens while plants are in bloom, cover them with row cover or old sheets. Put the cover on in the early evening and remove it in the morning once the risk of frost injury has passed.
After the harvest, the second-year canes that bore fruit will start to die. Remove second year canes in late summer or fall, cutting them off at soil level.
Fall-bearing raspberries produce fruit at the top of first-year canes, too. Remove only the portion of the first-year cane that fruited, not the entire cane, as this type of raspberry will bear fruit lower down on these same canes the following year.
During late winter, remove all weak, broken, diseased and insect‑damaged canes and narrow the rows to 12 inches.
Like raspberries, second-year canes of blackberries will start to die after harvest and should be removed. Unless there is a lot of cane disease, delay cutting off the canes as long as possible to allow the dying canes to move nutrients back into the crown and roots.
For trailing blackberries only (such as ‘Marionberry’ and ‘Olallieberry’): After you have removed the second year canes, trellis the first-year canes. If you live at higher elevations (above 500 feet) or in more exposed areas, leave the first-year canes on the ground throughout the winter. Protect the canes with straw and train them onto the trellis in late February after the threat of severe cold has passed.
For erect and semi-erect blackberries only (such as “Chester Thornless” and “Triple Crown”): In early spring (before budbreak), shorten lateral branches to 18-30 inches to make the vigorous canes more manageable.
Blueberries have superficial roots. For cold protection, mulch the plants with bark or sawdust. Blueberries in pots are most susceptible to winter injury because the roots are more exposed. Bury the containers in the ground or wrap them in a blanket or bubble wrap for protection
If you have had problems with mummyberry, a fungal disease that causes new leaves and flowers to wither and mature berries to shrivel and turn white (called mummies), take the following steps to control the problem:
• Remove the mummies from the planting and discard them (do not compost)
• In the fall cultivate the soil about an inch deep around the plants to bury any mummies
• During the dormant season, apply 2 inches of sawdust to prevent emergence of fruiting bodies
• In early spring, rake the soil around your plants to destroy any developing fungal fruiting bodies
Although blueberries can survive temperatures well below zero (to -20 or -30 degrees), heavy snow can damage the bushes by bending and breaking their branches. Remove the snow before it freezes to limbs and branches by gently brushing the branches upward with a broom. Do not attempt to remove ice encased on branches; let it melt naturally.
Blueberry branches are most productive when they are 3-4 years old. Productivity declines significantly thereafter. Pruning enhances the growth of new canes and removes older canes that are no longer productive. Prune your blueberries in late winter because plant structure is more clearly seen and healing of wounds is better.
Regardless of the berry type, clean up your berry planting now. Remove fallen leaves, decaying fruit and weeds. Compost only disease-free vegetation; burn or discard any that is questionable.
Most berries develop next season’s fruiting buds as the days get shorter and the temperatures cool; make sure your berries get 1-2 inches of water each week. Do not fertilize your berries again until next spring; applications of nitrogen in the fall can stimulate late growth that is prone to winter injury.
Jeanette Stehr-Green is a WSU-certified Clallam County Master Gardener.