A frequent question asked by strawberry growers in spring relates to the timing of straw mulch removal in matted row strawberry culture. Straw is often used to prevent winter injury in strawberry beds. With our unusually late spring this year, it is particularly hard to determine the exact timing of this important cultural practice.
The best method Michigan State University Extension recommends in determining the proper timing for mulch removal is to look for the beginning of leaf growth under the mulch. Strawberry growers will need to inspect their fields several times a week at this time in the annual spring green up period. Randomly pick a half dozen spots in your earliest variety and earliest site and gently pull the straw off of a section of row a few feet long. If you see newly emerging leaves – they may be a yellow color – that are beginning to emerge from the crown of the plant, generally that is telling you that the strawberries are ready to begin growth for the season and that straw needs to be removed. You can then recover these short sections of row.
Again, concentrating on the earlier fruiting strawberries is usually a technique that will help to pinpoint timing of straw removal. Move into the patch to do this sampling and avoid the temptation to look only at the ends of rows – the berries are always earlier than the rest of the planting.
The condition of your soil also is a factor in determining when to remove the straw mulch. If you are on heavy soil and your soil has not dried yet, either wait for a cold morning when there is a crust on the soil surface to reduce soil compaction or simply wait a few days for your soil to dry out more.
Lastly, before you remove straw, check the weather forecast. If cold weather is predicted, you should consider delaying a few days.
The typical time for removing straw in Michigan is mid- to late March for the lower half of the Lower Peninsula, mid- to late March for the northern half of the Lower Peninsula, and most likely early April in the Upper Peninsula. Strawberries growing close to Lake Michigan may also be uncovered a bit later than inland sites. However, the proper timing of straw removal varies greatly from year-to-year.
The earlier you remove the straw mulch, the earlier fruit will mature. Early growth may also necessitate more frost protection. For early springs like 2012, growers may consider delaying straw removal in order to delay harvest. Then again, in late springs like we are experiencing this 2014 season, there is also a danger of leaving straw on too long. A study was conducted a number of years ago in New England where straw was removed periodically over a six week period. The highest yields came from plants that were uncovered earliest in spring as was practical, following either snow melt or ability to move straw removal equipment through the field without creating ruts. The later the straw was removed, the more yield was reduced.
I also suggest that a light layer of straw be left on the plants. This layer would be about an inch thick. Leaves and flowers can grow up through this thin layer of straw. Many times this will help reduce disease problems later in the season and will also help prevent some weed seeds from germinating if bare soil is exposed to sunlight. Lastly, mulch removal just prior to a rain event helps the plants respond well and keeps the mulch in place.