Scaling analyses are performed for grafted polymers in marginally poor solvents, where the chains are not strongly collapsed. We obtain the first phase diagram for such systems which includes all three possible structures: layers, "mushrooms", and clusters. Clusters are found to exist in a region between the layer and the mushroom regimes. This may clarify the controversy over the existence of the cluster structure among previous investigations. Studies for the mushroom-layer transition are also presented. The transition is obtained at grafting spacings greater than the collapsed mushroom dimensions, accompanied by a mushroom-pancake configurational transition. Our predictions are in agreement with computer simulations.