I’m starting a thread to capture experiences anyone has had working with mesquite trees as bonsai. I was inspired by Hawaiian mesquite on the beaches on Maui, but was unable to obtain seeds due to agricultural restrictions. So, I decided to go with the next best thing and grabbed a bag of local seeds from a nursery in AZ.
My first pro tip is you absolutely need to soak the pods, scarify the seeds, and then soak the seeds again. Trying to break open the pods gracefully when they are dry is difficult and you end up with fibrous pod interior sticking to your seeds. After an overnight soak the pod splits easily and removing the seeds is a breeze.
The seeds themselves have a very tough outer layer that requires you need to puncture . I tried planting 20 seeds without scarification with a zero percent germination rate after 30 days. I then tried scarifying five seeds with a file and giving them a second 24 hour soak with a 100% germination rate within 3 days.
Do not skimp on the second soak. The inner seeds needs to be busting out of the outer covering completely before you plant. On subsequent trials I got impatient and gave them shorter soaking times and most of the sprouts were unable shed the outer layer.
In terms of planting medium, I found 100% perlite works best whereas 50/50 perlite coco coir seemed to be a death sentence. No idea on why though.
I hope someone trying mesquite for the first time finds this useful.