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| Photo: Strawberry field following straw removal. |
Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production
Straw mulch must be removed from strawberries when they first begin
growing in the spring. Once the straw is off, plant growth accelerates rapidly. Delaying mulch removal too far leads to delayed
harvest and decreased yield. The key is to balance straw removal with the weather, to minimize risk of late spring frost damage.
Each spring is so different in Minnesota, so it is a grower's challenge
figure out the ideal time to remove straw from strawberry fields.
This decision should depend on a few factors:
- Strawberry leaf growth under the straw
- Soil temperature and moisture
- The weather history and forecast
This year, our spring is off to a slightly slower start than in 2020 and 2021. We look at growing degree days to find out if our spring is "ahead" or "behind" the average.
For example: Based on three weather stations in southeast Minnesota, that region is 8 days behind 2021 and four days behind 2020. However, it is still 21 days
ahead of the 30-year average GGD for this day of the year due to overall long-term rising temperatures. The area between Alexandria and Albany is still at zero growing degree days according to two weather stations (base temperature 50 degrees F). See where your area stands by using the Integrated Plant Protection Center GGD tool and clicking on the weather station closest to your farm.
Therefore, straw removal may be occurring at about the same time as, or a week or two later than, it did the last couple of years, depending on your location. 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 moisture
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.
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.
Check the weather forecast
While delaying straw removal directly delays harvest and may reduce yields, early removal also increases 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.
Methods for removing straw
Managing risk - spring frost events
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| A freeze-injured strawberry blossom. Photo: Annie Klodd |
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 lower in seasons where growing degree days accumulate very slowly, 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:
Additional articles on timing of straw removal:
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