Anytime between now and middle May. It also depends on how quickly everything greens-up, so the early the better, since wet and new growth green will not burn. Needs to be warmer,60's, low humidity and enough wind to push the fire,15 mph, from the correct direction. Push to an oil road if possible. Burn mid-day to meet the above conditions,as the evening will have the opposite conditions. Call the fire dept to inform them of a controlled burn and consider a donation to the dept. and providing the post burn beer if they will be present at the burn. Good luck!