If you grow strawberries, you may be wondering when to cover them for the winter. Recently retired University of Illinois Extension Local Foods and Small Farms Educator Mike Roegge provides the following tips.
Straw is traditionally applied to strawberries when they have gone dormant. You don't want to cover them too soon as you can smother the plant. We've had a couple of days of 20-degree temperatures in December, so strawberries should be dormant. Dormancy can be noted as the plants will turn a slight purple/red color.
Roegge explains that the reason we cover strawberries is to reduce soil temperature fluctuations. Alternate freezing and thawing of the ground expand and contracts the soil, which can push strawberries up and out of the ground. This displaces roots and exposes the crown to damage or breakage. Maintaining a cover on the ground reduces the amount of temperature fluctuation.
"There are additional benefits to strawing as well," says Roegge. In the spring, having straw surrounding the plant reduces soil splashing, which can reduce or eliminate leather rot disease as well as keep berries cleaner.
Straw is the best material to use as air and water can both move freely through it. Wheat straw, oat, rye, or barley will do, whatever is available. Leaves are not suggested. Place at least 6" of straw over the plants. This should settle during the winter leaving 3-4" of cover.
Straw should remain on the row until spring. Remove the straw when soil temps reach 40-42 degrees in the spring. When removing the straw, rake most but not all the straw from the row. Leave an amount to keep the soil covered within the row.
Roegge also provides some early winter garden advice for raspberry and asparagus growers.
"Raspberries plants that have fruited on second-year canes can be removed now or in the spring prior to green up." These canes will be brown or gray in color. The primocanes that grew this year (and may have set a late crop of berries) will produce a full crop next summer, do not prune these out. But do thin them to 6 or so of the larger canes per foot of row. Depending upon trellising or not, cut back the canes to 4-6 feet in length and trim back branches to 10-12".
For more information on growing small fruits, go to http://urbanext.illinois.edu/fruit.