Mulch Materials
Mulch materials include straw, hay, wood, aggregate, and one combination of straw and hydraulic mulch (Type 4). Other than Type 4, these mulches are not hydraulically applied. Hydraulic mulches and tackifiers are defined in MnDOT Spec 3884 and are explained on the hydraulic mulches and tackifiers web page. Requirements for the use of all types of mulches are found in MnDOT Spec 2575.
Straw Mulch
There are four types of mulch in MnDOT spec that consist of straw or similar material.
Type 1 Mulch
Sometimes used on MnDOT projects for temporary and permanent stabilization, Type 1 mulch is grain straw, hay, or cuttings from agricultural grasses and legumes. It must be free from noxious weeds as well as cattails, reed canary grass, birdsfoot trefoil, and queen anne’s lace. Certification is not required and there is no approved products list for Type 1 mulch.
Type 3 Mulch
Also called Certified Weed Free Mulch, Type 3 mulch is the most commonly specified type of straw mulch on MnDOT projects. It is the straw mulch with the most stringent quality assurance to help prevent the spread of noxious weeds. There is no approved products list for Type 3 mulch but it must be certified by the Minnesota Crop Improvement Association (MCIA). This certification is indicated by a MCIA-issued tag that must be attached to each bale before it leaves the production field.
For more information on certified weed free mulch visit the MCIA Certification Services web page.
For help finding certified weed free mulch visit the MCIA Where to Buy web page.
Type 3 Mulch is not allowed from outside of Minnesota unless it has been certified by the MCIA.
Type 4 Mulch
Type 4 is a combination of straw mulch (either Type 1 or Type 3) and Stabilized Fiber Matrix, a type of Hydraulic Mulch. The straw component of Type 4 mulch does not have an approved products list but the Stabilized Fiber Matrix component must be on the Hydraulic Erosion Control Approved Products List.
Type 8 Mulch
Type 8 mulch consists of hay harvested from stands of native prairie grasses. It must be free of noxious weeds as well as cattails, reed canary grass, birds-foot trefoil, and queen anne’s lace. There is no approved products list for Type 8 mulch.
Wood Mulch
Wood mulches do not have an approved products list but they are subject to visual inspection by the inspector. Wood mulches are also subject to quarantine requirements regarding invasive forest pests such as the emerald ash borer. More information can be found in Spec 3882 and by contacting the Minnesota Department of Agriculture.
Type 5 Mulch
This consists of waste wood obtained from clearing on the construction project and must be processed in a chipper, hammermill, or tub grinder. It has many erosion and sediment control uses on construction projects. It is more coarsely ground and may contain larger pieces than Type 6 mulch.
Type 6 Mulch
Type 6 mulch is similar to Type 5 but is more finely ground, with a smaller maximum piece size. It is typically used for landscaping projects in keeping with MnDOT Spec 2571. The contractor must submit a Certificate of Compliance from the manufacturer stating that the product meets the requirements of Spec 3882.
Aggregate Mulch
Type 9 Mulch
This mulch consists of 3/8” to 2” rock that is used for stabilization where vegetation is not expected. There is no approved products list for Type 9 mulch but the contractor must provide a Certificate of Compliance stating that it meets the requirements of Spec 3882.
Specification
Requirements for mulch materials are defined in MnDOT Standard Specifications for Construction, available on the MnDOT Spec Book web page. Open the document and search for the following:
- Installation requirements: 2575 Establishing Turf and Controlling Erosion (see 2575.3 C Applying Mulch)
- Material Requirements: 3882 Mulch Materials
Approved Products List
There is no approved products list for most of the mulch materials described on this page, with the exception of the Stabilized Fiber Matrix component of Type 4 Mulch. Some of the products require Certificates of Compliance or other forms of certification. Read the description of the product in question for more information.