The precautions for wood ashes are similar to those of lime. Wood ashes are alkaline and will raise the pH of your soil over time, though to a lesser degree than lime applied at the same rate. Thus, you will need to take a soil test in order to determine the pH of your particular soil. People sometimes use coal ashes. However, coal ashes and large amounts of wood ashes should be avoided because of toxicity concerns. If you will be using wood ashes, do not apply them near seedlings or use them on acid-loving plantings such as rhododendrons and azaleas. If the ashes come from treated lumber, I would use great caution and would not apply them to the vegetable garden. To obtain a soil test kit, simply call or stop in at your county cooperative extension office. They will sell you a soil test kit that comes with complete instructions. For more information about soil test kits in Pennsylvania, go to: http://www.aasl.psu.edu/HOWTO.HTM