Dwarf Juniper and Blueberry

Asked March 9, 2016, 12:05 AM EST

I have read that juniper is allelopathic.
I had planned to plant a dwarf juniper next to an unhappy, lonely blueberry bush as an acidifying companion, along with some creeping thyme, and possibly basil. Now I am wondering whether this is a good idea? I seem to find conflicting information on the Web as to whether juniper and blueberries are companionable. Both are acid loving, but the juniper is putatively allelopathic. Can someone please clarify this confusion for me? Thanks! Oh...and IF Juniper is allelopathic, any chance of it killing or at least out-competing wedelia, ginger, or albizia? Would love help getting rid of those organically! Seems unlikely due to different root depth, but worth a shot asking.

Maui County Hawaii junipers juniper horticulture

1 Response

Aloha and thank you for using AaE. There is evidence of Juniper being allelopathic in addition to it's needles acidifying soil conditions. Additionally, planting under or next to any tree will result in competition for resources (i.e. light, water, and nutrients). Trees can have deeper and more extensive root systems enabling them to often be better competitors for resources. Hence, I don't think the blueberry will benefit from the Juniper as a "companion". Even though both types of plants prefer acidic soils they will still both be competing for the same resources and the dwarf juniper will most likely win. Studies on growing blueberries on the Big Island and anecdotal evidence in Maui, suggest that blueberries do not grow as well when planted directly into the ground and instead suggest growing them in containers. For additional information on growing blueberries in Hawaii please see http://www.ctahr.hawaii.edu/oc/freepubs/pdf/F_N-46.pdf.
In regards to using Juniper to control weeds or other invasive species, while you may see some slowing of growth or coverage surrounding the Juniper, it is unlikely a single dwarf juniper will be able to mitigate your existing wedelia, ginger, or albizia plants. All of these species are considered invasive in Hawaii and have traits that enable them to spread and regenerate relatively quickly, and out compete other species for resources.