Blueberry Mulching and Water Management 

By Anya Osatuke, Cornell Cooperative Extension Harvest New York 

Mulching blueberries is recommended for several reasons: 

• Blueberries have shallow roots, and a layer of mulch retains soil moisture in the root zone.  
• Mulch can prevent weed seeds from germinating, or smother weeds after germination.  
• Pests can be deterred by reducing trapped moisture aboveground, below the canopy.  
• Pests can be smothered by a springtime application of mulch. 

There are three main forms of mulch available for blueberry growers: woody mulch, fabric mulch, and living mulch. Woody mulch and fabric mulch are recommended over living mulches.  

Woody mulches 

Woody mulches were historically the standard amongst blueberry growers. Many municipalities have had wood chips, corn silage, or sawdust freely available as these are byproducts of other local industries. Softwood mulches are most preferred because of their lower pH. However, any mulch that wasn’t treated with dyes or herbicides will improve planting health by suppressing weeds, retaining soil moisture, increasing soil organic matter, and, if applied in early spring, smothering pests. 3 inches of mulch per season is optimal, and a mulch or manure spreader will help speed the task. Woody mulches can help retain soil moisture, but prolonged droughts are becoming more common: irrigation is helpful between May and July. Blueberries need at least 1 inch of water a week. If using a plastic dripline, avoid sawdust as rodents will tunnel through and nibble on it. 

There is one pest to be aware of when sourcing wood chips: The jumping worm (multiple species of worms in the genus Amynthas). This worm is likely to live in the upper surface of any mulch pile exposed to the soil. The worms are almost invisible until hatch in late April or early May. Inspect mulch piles in summer or fall before buying and transporting to your farm.  

Fabric mulches 

Fabric groundcovers do not contribute organic matter, but their impermeable surface helps retain moisture. The fabric groundcover is typically installed alongside a dripline. A tarp cart system or other means of holding tensile strength on the mulch as it is maintained can be very helpful.  

Fabric mulches work best when applied and removed every growing season. Over the years, weeds break down the mulch and new blueberry canes may be suppressed. By using two overlapping sheets of mulch per row, growers can make space for blueberry bushes in the middle of the two sheets.  Annual maintenance of the fabric mulch allows for easy inspection of the dripline. The final benefit of this system is the ease of making ground applications of granular fertilizers and amendments, such as sulfur, compost, and other fertilizers. Compared to fertigating through the dripline, granular amendments are cheaper and less likely to contribute to wear and tear of the irrigation system.  

Living mulches 

 Various species of turfgrass are commonly used as living mulch, but sweet woodruff (Gallium odoratum) and creeping buttercup (Ranunculus arvensis) have been evaluated as well. Living mulches were not found to support blueberry growth as well as fabric or woody mulches.  

Citations: 

Costs of Establishing Northern Highbush Blueberry: Impacts of Planting Method, Fertilization and Mulch Type | James W. Julian, Bernadine C. Strik, Handell O. Larco, David R. Bryla, and Dan M. Sullivan | 2012 

Determining the Effect of Biodegradable and Living Mulches on Annual Weeds and Growth of Newly-Planted Blueberry | T. Miller, L. Wasko-DeVetter, D. Harteveld | 2018 

Jumping Worm (Amynthas spp). | Cornell Cooperative Extension Columbia and Greene Counties | 2021