Manage next year's strawberry weeds this fall ( June-bearing focus)

Article updated and reposted by Madeline Wimmer, UMN Extension Educator, Fruit Production

Original article by Annie Klodd. Reviewed by Emily Hoover and Jim Luby. 

Image: It's normal for a few weeds to be in a strawberry patch during the fall, even with excellent weed control. Photo: Annie Klodd

Managing plant competition between June-bearing strawberries and weeds within and between matted rows is one of the most time consuming tasks required. Taking time to be methodical with your weed management approach is well worth it to reduce overall labor efforts, freeing up time for other production tasks. 

This article focuses primarily on conventional management practices, but some practices can be applied for Organic and similar managed matted row fields. 

Article main points: Follow these four tactics to reduce next year's weeds 

1.        Remove weeds before they shed seeds
2.        Cultivate between rows
3.        Carefully apply certain pre-emergent herbicides for conventionally managed beds
4.         Mulch late in the fall, for winter protection, which can also provides significant weed suppression the following season

Removing weeds before they shed seeds (details)

It's a worthy use of time to invest in the removal of large weeds before they drop their seeds. 

Why this works: One Palmer amaranth plant can produce between 100,000 to 1,000,000 seeds (source). One lambsquarter plant produces 72,500 seeds on average (source), and one Eastern black nightshade plant produces up to 825,000 seeds (source). While not all of these seeds are guaranteed to survive and germinate the following year, even a portion of these weeds now.

Take note that weeds that already have seeds on them must be taken out of the field for this to be effective. If they haven't produced seeds yet, they can be dropped in place.

A strawberry field with a heavy infestation of smartweed or knotweed. The plants have produced seed that will reproduce next year unless the plants are removed for the field. Photo taken by Annie Klodd.

 

What to do with removed weeds: 

• Composting can kill the seeds if the pile is turned properly, and if the temperature gets high enough for a long enough time period. SARE has a nice guide on how to create proper compost. 
• Burning weed seeds at prolonged extreme heat can also kill them. This requires dense, dry piles, as well as a burn permit is some places.  
• At Virginia Tech in 2017, Dr. Michael Flessner's research group killed Palmer amaranth seeds by piling the plants in narrow (3-ft wide) windrows and burning them at extreme temperatures. In the report, they write, "the windrow needs to reach 750-930 F for 10-30 seconds to kill most weed species, but some weeds such as crabgrass will be killed when exposed to 185 F for 20 seconds." I recall that this tactic worked when the piles were dry, but struggled after a brief rainfall (read the report here).

Cultivate between rows (details)

Small weeds between strawberry rows can be terminated in the fall via cultivation using tractor attachments (tine weeder or rotary cultivators adjusted to row settings) or hand tools. To some extent, low mowing can also help. Be careful not to run cultivators and mower decks too close to strawberry crowns to prevent injuring the plants (see notes below on rhizomatous weeds like quack grass and Canada thistle). It's recommended to keep the aisles in between the strawberry rows 12-18 inches wide.

In addition to weed management, fertilizers or compost can also be incorporated during fall cultivation.

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The nutsedge infestation in this otherwise productive field is too large to hand-pull. It would benefit from careful application of a pre-emergent herbicide for the following season.

Fall mulching (details)

We'll cover more information later this fall in regards to timing (make sure plants are fully dormant) for mulching June-bearing strawberry matted row fields during the fall. For now, take note that this practice can be helpful to overwintering strawberries, especially during years when snow cover is low, which was the case in 2024/2025 winter in Minnesota. 

Mulches suppress weeds in the spring by blocking out light. The amount of light that is blocked will depend on the material being used and how thick it is. While straw is commonly used and is a great option, it should be applied in a thick layer (3-5 inches) because it tends to block less light than sawdust and wood chips. Avoid using hay and verify the quality of straw being used to prevent accidentally introducing new weed seeds. 

Managing weeds that spread by rhizomes

Canada thistle and quackgrass are two of the toughest weeds for fruit growers in Minnesota. They spread rapidly via rhizomes and have few safe and effective herbicide remedies.  Early fall is a good time to hand-remove or spray them with labeled systemic herbicides. Their root systems are relatively depleted of energy in the fall, and herbicides will be translocated to the root/rhizome system.

As we mentioned cultivation above, it should be noted that cultivation is not recommended if the problem is Canada thistle or quackgrass, and instead opt for hand-removal and mowing, although mowing alone may not be sufficient to control them. Their roots can produce new plants if they are torn up and re-buried, spreading the weed.

 

Example for controlling nutsedge using conventional herbicides (Midwest Fruit Pest Management Guide instructions):

• For a fallow field that will be planted into strawberries next spring: You may spray Sinbar WDG pre-emergent herbicide this fall after the plants are dormant and before spreading straw. Apply Spartan in the spring right before planting. If the field is currently in another crop, wait until the crop is harvested before spraying.
• If a field is currently in strawberries and those strawberries will be overwintered: Apply Sinbar WDG this fall after the plants are dormant and before spreading straw.  Do not use Spartan in this scenario, because it is intended for pre-plant only; it can cause severe injury if used after planting.
  
• Note on herbicides: 
• Some varieties of strawberries are sensitive to Spartan. Stay within labeled application rates and read all label instructions. 
• Glyphosate can be spot-sprayed between rows to kill emerged nutsedge. Do not spray it over the rows.
• Sinbar and Spartan have "fair" efficacy on nutsedge
• Hand-remove nutsedge plants over 6 inches tall that escape herbicide control. 

Read this article from University of Massachusetts Extension for more strawberry herbicide options and other important information on their application.

It's worth it to slow down and follow best practices when using herbicides on strawberry beds: Severe strawberry injury can result from mis-timing or mis-applying these products. Use spray guides and consult the labels for more information before spraying any of these products. 

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CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Be sure that the plant you wish to treat is listed on the label of the pesticide you intend to use. And observe the number of days between pesticide application and when you can harvest your crop. Remember, the label is the law.