It is renovation time in perennial strawberry

Renovate strawberry fields after harvest to improve crop production next year.

Renovated strawberry field
Renovated strawberry field. Photo by Mark Longstroth, MSU Extension.

Strawberry harvest is about finished in Michigan for this year. Effective post-harvest tillage and weed control are important for strawberry plant regrowth and fruit production next year. A healthy and weed-free strawberry patch should remain productive for four to five years with good renovation and late season practices.

The renovation process includes applying fertilizer, tillage and narrowing of the rows, mowing and herbicide application. If there are many broadleaf weeds in the field, it may be necessary to apply Formula 40 (2,4-D) before other practices. If the field has a moderate number of weeds, the herbicide application can wait until after tillage and mowing.

Broadcast 300 pounds per acre of 20-20-20, or the equivalent amount of NPK, to the field before tillage. An adjustable tiller that straddles the row is the most effective machine for renovation. Narrow the rows to 10-12 inches. A wider original row results in low new-plant density in the middle of the rows next year. The remaining plants in the rows will send out runners that take root and become the fruiting plants the following year.

The next step is mowing the remaining plants to a height of 4-5 inches. This should remove most of the existing strawberry foliage and leave low-growing weeds in the rows. If 2,4-D was not applied previously, it should be applied after mowing if broadleaf weeds are present. A postemergence grass herbicide such as sethoxydim (Poast), clethodim (Select Max) or fluazifop (Fusilade) should be applied to kill annual and perennial grasses. Include an adjuvant with the grass herbicide. If most of the broadleaf weeds are composites (e.g., Canada thistle, dandelion, mayweed, ragweed, groundsel), clopyralid (Stinger) may be used instead of 2,4-D. Stinger has a Michigan 24c Label and is not labeled for this use in all states. Do not include an adjuvant if Stinger is included in the spray mix.

After tillage, apply residual herbicides to control weeds for the rest of the summer. Herbicides labeled for use at renovation include Devrinol, Dual Magnum, Spartan, Prowl H2O, Sinbar and Ultra Blazer. For broad-spectrum, full season weed control, include two residual herbicides in the post-renovation application. Effective mixes include a primarily grass herbicide (Devrinol, Dual Magnum, Prowl H2O) and a primarily broadleaf herbicide (Spartan, Ultra Blazer). Read labels to determine which weeds will be controlled for your situation.

Sinbar is a very effective herbicide but may stunt strawberry on light sandy soil. Do not use Sinbar on soils with less than 1% organic matter (OM) or over 70% sand. Devrinol controls annual grasses for three to four weeks. Spartan is effective against several composites. Chateau also may be used on strawberry but should only be applied to aisles between rows. It is most appropriate for strawberry grown on raised beds on plastic mulch.

Spartan, Sinbar, Ultra Blazer, Prowl H2O and Dual Magnum also may be applied in late fall before spreading of straw mulch. An effective herbicide application in fall should provide good weed control through the harvest season the next spring. Check herbicide labels for maximum use rates per acre per year to avoid over-application. You can read labels at CDMS.

There are several generic clopyralid herbicides available. Apply clopyralid in early to mid-fall to control legumes (clover), composites (asters, daisies, dandelions, thistles), nightshades (including groundcherry), smartweeds (including prostrate knotweed, red sorrel, and wild buckwheat) and plantains. Another grass herbicide application may be made at the same time. Fusilade is the most effective postemergence herbicide for quackgrass control. Some weeds will escape all of these herbicide applications and should be removed by hand.

On light soils, another application of 50 pounds nitrogen will give the plants a boost and prepare them for fall dormancy. This should provide more vigorous growth in the spring. Timely irrigation during summer and early fall will promote plant growth and health. This will result in production of many fruit buds and a larger crop the following year. Another application of 50 pounds nitrogen may be needed about May 1 the following year on light soils. If the plants appear to slow down their growth in spring, apply the extra nitrogen. Over-application of nitrogen may result in excess plant production and reduced fruit production. Every situation is different, so observe your plants regularly in the spring.

Current weed control recommendations for all vegetable crops area available in Michigan State University Extension bulletin E433, “Weed Control Guide for Vegetable Crops.”

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