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Strawberry Growers take Note!

Karl Foord - Extension Educator, Horticulture

Removing straw mulch on strawberries using lilac buds as an indicator

Sometimes nature is a better indicator of the best time to take action than our measuring equipment. Researchers Terry Nennich and Dave Wildung attempted to determine the best time to remove the straw mulch on strawberries using growing degree days (GDD) which are a measure of heat accumulation. GDD are often used to predict when a plant might flower, or how developed a pest might be to optimize the timing of control.

Karl Foord

Photo 1: Buds of Common Lilac (Syringa vulgaris)

In this case Terry and Dave found complications that made GDD a less reliable indicator for the timing of mulch removal. Given this they looked for other signs in nature that might be more useful. Their conclusion was that when the lilac buds open, it is time to take off the straw. This correlated well with the end of strawberry dormancy. Timing is critical as a delay in removal was shown to reduce both the total yield and the size of berries. The longer the delay the greater the loss in yield.

To this end please observe the pictures of bud break in common lilac (Syringa vulgaris) in photo 1 and in dwarf Korean lilac (Syringa meyeri 'Palibin' in photo2. Both taken May 6, 2013 in Chaska, MN.

Karl Foord

Photo 2: Buds of Korean Lilac (Syringa meyeri 'Palibin')

Is it time to remove the straw mulch from your strawberries? What is the status of the lilac buds in your neighborhood?