Hi, Well it sounds like you might have several problems here. First, if you have heavy clay soil, you won't be able to grow very much and if you have exposed roots I wonder if you also have a shade problem from big trees nearby. The best way to have a good garden is to improve your soil. With clay you'll need to add a lot of fresh soil and organic matter to make it more organic and drain better. However, if you have a lot of exposed roots, you don't want to cover them because you could hurt the tree they are coming from. To grow any vegetables and most flowers you need a spot that gets at least 6 to 8 hours of direct sunlight a day. You don't give me a lot of information here, but it may be that you need to locate the sunniest spot you have and build some raised beds and fill them with improved soil. That might be easier in the long run. By the way, whoever told you that lavendar could grow anywhere gave you bad advice. Lavender requires very good drainage and will die quickly in heavy clay soil. It prefers a loamy, sandy soil that does not get too muddy. Ultimately, the only way you'll ever have a good in-ground garden is to improve your soil.