I have a large patch of blackberry bramble that is intertwined with some arborvitae that I'm cutting down. I was wondering if it is a good idea to rent a wood chipper and mulch all of it and use it as sheet mulch for a garden next spring? My concern is that I would be spreading the bramble and the mulch could be thorny or would letting the mulch pile heat up and breakdown kill the bramble?
Multnomah County Oregon
Shredding the blackberry/arborvitae, then using it as sheet mulch next spring should work well. There would be thorns in the mix, though, and I'm not sure how broken down they would be by next spring.
The blackberries should not grow back from the shredding. Plants spread primarily from roots in the crown and from daughter plants which develop from first year canes when they touch the ground.
This article has good information on blackberry control methods, including shredding and use as mulch in the Manual/Mechanical Control Methods section, Controlling Himalayan Blackberry https://www.invasive.org/gist/moredocs/rubarm01.pdf.