.We used a flamer for weeds in the garden. It scorches the top but does not kill the roots of perennial weeds, they just came back stronger. If you use a flamer, it is better on hard surfaces. Someone was using a flamer once and the mulch caught on fire, burned a rosemary and part of the fence. The operator did not even notice since his back was turned and he was about 40 ft away. A couple of people went out and doused the fire. The rosemary eventually died, the fence was a goner.
Happy gardening in Hawaii. Gardens are where people grow.