Most cover crops are tilled in when they begin to flower. You don't want them to go to seed or make pods because the energy is transfering to the pods. If you want the added nitrogen it is best to have inoculated the seeds when they were planted. Mowing or tilling them in is what you want to do. The nitrogen stored in the plants and the nodules are not released until they decompose.
Happy gardening in Hawaii. Gardens are where people grow.