its not listed on the deciples of the land website that i've seen. but Walnut can also be found at bloodshore
thats where i've been getting most of my supply from as i've been stocking up for the last push on CRP

if you wanna check it out
north of bloodshore you have the road on the west side there is 3 trees, directly north almost right at where one of the spots for the buffalo faction NM is another tree. then you have 3 trees on the east side of the road.... the east side is a little more spread out

35-18, 36-19/20, 38-19, 37-18, 38-21

using the YG map for the grid marks since we can't get online right now lol