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Birch chips #408190 - Ask Extension


Birch chips #408190

Asked June 19, 2017, 11:44 AM EDT

Can I mulch blueberry bushes with birch chips?

Spokane County Washington

Expert Response

Hello, and thank you for contacting us,

I wasn't sure about the answer to your question, so I looked at some information from Professor Bernadine Strik from Oregon State. She has done extensive work with berries. The short answer is that you can mulch your blueberries with birch chips.  You might need to give the plants a little extra fertilizer, because some of the nutrients in the soil will be temporarily absorbed by soil organisms starting to breakdown the wood chips.  I've copied an answer that Dr. Strik gave to a similar mulch question below.  The original question was about douglas fir sawdust, but if you read through, you'll see how it applies to wood chips:
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 hope this answers your question.  Let me know if you need any other information!
Tim Kohlhauff Replied June 19, 2017, 12:57 PM EDT

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