Mulch for blueberries
I have a compounded question. I recently planted 10 blueberry plants and would like to know what is the best mulch to use. I already mulched with peat moss but i have read conflicting statements about using it as mulch. If you think that pine needles make a more suitable mulch for blueberries, where can I purchased them in the Portland area?
Washington County Oregon
I hope you have established your blueberry plants with the recommended pre-plant practices that will help ensure success -- particularly soil pH modification, if required. Please refer to the Growing Blueberries in Your Home Garden publication, EC 1304, available from OSU at: http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/12202/ec1304.pdf;jsessionid=CB6A3EBD1A...
You will note that we generally recommend Douglas fir sawdust as a mulch because it's usually readily available and it has a pH of about 4.5 (good for blueberries). However, there are other products that might be more readily available for home gardeners. For example, bark mulch is a good choice (also has a low pH). The reason we use a mulch is that blueberries like high organic matter soils, the mulch helps control annual weeds, and helps conserve soil moisture making irrigation management easier. We have studied various mulches and have some other specific comments/recommendations as a result. Homegardeners often like to use yard debris compost as a mulch/fertilizer. However, this material has a high pH (7 to 8). While a little bit can be added as a mulch, it's best to avoid using a lot of this type of product when mulching blueberries. Also, avoid manures or horse bedding for the same reason. Managing soil pH should be your first concern. While peat moss is acid, it is very expensive and when it dries out its hard for water to get through it (hard crust layer). For these reasons, I wouldn't recommend peat as a mulch. The second consideration should be how will the mulch affect weed growth/management? Sawdust works pretty well as seeds don't germinate readily in sawdust. Compost holds moisture better and is nutrient rich so weeds germinate readily in compost. Finally, we've looked at using porous landscape fabric (see picture below where compost mulch is in foreground, sawdust in middle and weed mat further down the row). Weed mat or landscape fabric controls weeds well, but you would need to have a drip irrigation line under the weed mat or the plants may not get watered well enough. It's also best to put some organic matter under the weed mat, like bark or sawdust -- no more than 2" deep. It's easier to manage a weed mat mulch when the weed mat is zippered with pins holding it in place (see picture); this way you can open the weed mat to add any needed fertilizer. Finally, if you are adding an organic mulch like sawdust, do not put on more than 3 inches at once so plant roots don't suffer. You will need to renew the sawdust mulch every few years to maintain the 3 inch depth.
Thank you very much for your very helpful response.