When you try to burn it, the sap produces a strong tasting smoke and turns your meat black. Also when you try burning green wood, it is hard to reach a good temperature because all the moisture in the wood almost puts the fire out while it's burning. Cured woods light easily and will maintain a good cooking temperature for several hours with very little maintenance. Also, cured wood will produce a good tasting smoke flavor that won't be too strong. There are several ways to control the amount of smoke taste you apply to the meat you're cooking.
Different hardwoods have different tastes.
Mild smoking woods are Pecan, Apple, and Peach. Medium smoking woods are Hickory, White Oak and Cherry. Heavy smoking woods are Mesquite, Blackjack Oak, and Red Oak. Any Hardwood that bears a nut or fruit is suitable to cook with. Use well seasoned wood.