Mulching Blueberries - Ask Extension
I have heard conflicting information on how to mulch blueberries. The information in the OSU publications say to mulch 2 inches the 1st year, then ov...
Knowledgebase
Mulching Blueberries #170994
Asked March 22, 2014, 12:59 PM EDT
I have heard conflicting information on how to mulch blueberries. The information in the OSU publications say to mulch 2 inches the 1st year, then over the years increase up to a total of 6 inches of sawdust mulch. The publication also mentions putting the mulch all around the plant. I have seen commercial fields with mulch and they put it up all around the plant as well as up the canes. One speaker I listened to said not to put the mulch up the canes. I realize that mulch should not be put up onto tree trunks, but I do not think the same is true for blueberries. So my question is.... can the mulch be put 6 inches up the blueberry plant? And is it possible for Professor Bernadine Strik to answer this question? Thank you.
Clackamas County Oregon
Expert Response
Hello,
I do recommend starting new plantings with a mulch of about 2 inches to 3 inches deep covering the in-row area to about 4 ft wide or an area around a singly planted bush about 4 ft in diameter. I do recommend putting this mulch (only about 2 to 3 inches deep) totally around the plant. The mulch should be flat in this area, not piled up higher around the plant. It's okay for it to be in contact with the canes. You should not see a "volcano" of mulch around plants. The mulch decomposes over time so every couple of years add another 2 to 3 inches of mulch. When the plants are mature (after 8 years in the ground) you may have a total of 6 inches of "mulch" but 3 inches or so will be relatively new/fresh mulch and the rest will be decomposed organic material (a good thing for blueberries).
There are a considerable number of options for mulching blueberries. The objectives of organic mulches such as douglas fir sawdust are to add organic matter to the soil over time, help conserve soil moisture, moderate soil temperatures and help control annual weeds. Blueberry plants grow best in an acid soil (pH 4.5 to 5.5) and like high organic matter. The pH of douglas fir sawdust is about 4.2. There are other low pH mulch options including bark mulch (a great option), wood chips, and pine needles -- all have a relatively low pH. Note that if you use a material like wood chips, you will need to watch the plants carefully as adding a more woody mulch like chips to the soil surface means you'll have to add more nitrogen fertilizer (these products take a longer time to break down and the bacteria that break down these materials use nitrogen meaning the plants have less available for their growth). Other options people think of are composted manures and yard debris composts (typical yard composts). Unfortunately both of these options have a very high pH ( about 7 to 8); for this reason do not use these products as a mulch alone. If you add 3 inches deep mulch made solely of composted manure or yard compost, the pH will be too high for good blueberry growth. You can use a little bit (1/2 to 1 inch deep) of this type of product, but then you should put about 2 inches of bark or sawdust on top to avoid too high of a soil pH and poor blueberry growth. Finally another option for mulching is to put down some bark (about 1 to 2 inches) and then top this with weed mat or porous landscape fabric (black) -- this really helps minimize weed growth. In this case you would need to put drip irrigation under the weed mat to ensure plants can get enough irrigation water in summer.
I do recommend starting new plantings with a mulch of about 2 inches to 3 inches deep covering the in-row area to about 4 ft wide or an area around a singly planted bush about 4 ft in diameter. I do recommend putting this mulch (only about 2 to 3 inches deep) totally around the plant. The mulch should be flat in this area, not piled up higher around the plant. It's okay for it to be in contact with the canes. You should not see a "volcano" of mulch around plants. The mulch decomposes over time so every couple of years add another 2 to 3 inches of mulch. When the plants are mature (after 8 years in the ground) you may have a total of 6 inches of "mulch" but 3 inches or so will be relatively new/fresh mulch and the rest will be decomposed organic material (a good thing for blueberries).
There are a considerable number of options for mulching blueberries. The objectives of organic mulches such as douglas fir sawdust are to add organic matter to the soil over time, help conserve soil moisture, moderate soil temperatures and help control annual weeds. Blueberry plants grow best in an acid soil (pH 4.5 to 5.5) and like high organic matter. The pH of douglas fir sawdust is about 4.2. There are other low pH mulch options including bark mulch (a great option), wood chips, and pine needles -- all have a relatively low pH. Note that if you use a material like wood chips, you will need to watch the plants carefully as adding a more woody mulch like chips to the soil surface means you'll have to add more nitrogen fertilizer (these products take a longer time to break down and the bacteria that break down these materials use nitrogen meaning the plants have less available for their growth). Other options people think of are composted manures and yard debris composts (typical yard composts). Unfortunately both of these options have a very high pH ( about 7 to 8); for this reason do not use these products as a mulch alone. If you add 3 inches deep mulch made solely of composted manure or yard compost, the pH will be too high for good blueberry growth. You can use a little bit (1/2 to 1 inch deep) of this type of product, but then you should put about 2 inches of bark or sawdust on top to avoid too high of a soil pH and poor blueberry growth. Finally another option for mulching is to put down some bark (about 1 to 2 inches) and then top this with weed mat or porous landscape fabric (black) -- this really helps minimize weed growth. In this case you would need to put drip irrigation under the weed mat to ensure plants can get enough irrigation water in summer.
