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When to Remove Straw from Strawberries in 2020

Photo: A strawberry field at Rod's Berry Farm, Cambridge, MN, in summer 2019. Annie Klodd

Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production

Straw mulch must be removed from strawberries when they first begin growing in the spring. Delaying mulch removal too much leads to delayed harvest and decreased yield. However, removal timing must also be balanced with the weather, to minimize risk of late spring frost damage.

Each spring is so different in Minnesota, that it is challenging to figure out the ideal time to remove straw from strawberry fields. Therefore, this decision should be made depending on a few factors:
  1. Strawberry leaf growth under the straw
  2. Soil temperature and moisture
  3. The weather forecast
This year, our spring has started relatively early. Therefore, straw removal will likely occur relatively early as well. It will most certainly be earlier than last year (2019), when we still had plenty of snow on the ground at this point in the season. Here are some guidelines for deciding when to remove straw:

Check for strawberry leaf growth under the straw

Go to your strawberry field every couple of days, and check for the beginnings of leaf growth under the straw. Do this by pulling away the straw on a few feet of row, at 6-12 places around your field. Avoid using the field edges, because the plants on the edges tend to start growing sooner than the rest.

Check the early fruiting varieties first, as they will likely push leaves earlier than later fruiting varieties.

The new leaves may be yellow, but if you see them starting to emerge from the crowns, this is one sign that it is time to start removing straw.

Check the soil temperature and wetness

In addition to checking for leaf growth, soil temperatures should also be consistently at or above 40 degree in the top 2-4 inches before straw is removed. Farms in southern Minnesota may have already reached these temperatures.

Ideally, wait to enter the field with a tractor until the soil has dried out somewhat. Driving heavy equipment on wet soil contributes to soil compaction. I understand that waiting for the soil to dry is not always possible in our climate.

Check the weather forecast

Weather stations I checked in southern Minnesota are currently 12 days ahead of the 30-year average in terms of growing degree days (Integrated Plant Protection Center).

While delaying straw removal directly delays harvest and may reduce yields, early springs such as this year (2020) also increase the chance that plants will start producing blossoms early and become vulnerable to late spring frost events. This may encourage some growers to consider waiting a few days past when leaves have started to form, in order to reduce the risk of cold temperatures injuring the plants.

Look at the forecast for your area of the state to determine whether there is a cold event predicted for the few days following your intended straw removal. If there is, you may consider delaying by a few days.

In the Twin Cities, average daily temperatures have stayed between 37-49 degrees F for the last 7 days, with a low temperature of 29 degrees on March 26 (National Weather Service). Temperatures are predicted to stay above freezing for at least the next 2 weeks (April 16).

Methods for removing straw

For smaller operations, straw can be removed with hand rakes and some quality family time outside.

Rod Elmstrand at Rod's Berry Farm in Cambridge, MN shared with me that he uses a modified hay rake on a 3-point hitch, where the height can be raised on lowered depending on the level of the field.

Many larger farms also use specially designed commercial mulch removers that are PTO or wheel driven.

Whichever method you use, try to keep a thin layer of straw, no more than in inch, over the plants to help suppress weeds and protect the plants from disease transmission via soil splashing.

Managing risk - spring frost events

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Despite our best efforts to remove straw at the correct time, the risk always remains that we will have a late frost event weeks after straw removal, which injures the blossoms and reduces yield. This risk is generally higher in seasons where growing degree days start accumulating earlier in the spring, like this year.

Growers should always be prepared for this possibility, especially as our climate changes and spring temperatures become less predictable. Two common strategies for frost injury mitigation on strawberries include:

There is a lot of great information online from various universities, describing how to use irrigation and row covers for frost protection (see links directly above). However, I will also try my best to provide information in future newsletter articles.

Additional articles on timing of straw removal:

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