The addition of some Aluminum Sulfate on the surface of a plant will increase acidity for acid loving plants. Taking care also means protection. As the weather improves it encourages the growth of the undesirable population of aphids, green flies, spider mites, white flies, and scale. If Junipers appear to be yellowing or looking sickly - suspect spider mites. In Pines, if there is evidence of a white woolly substance in the interior of the tree - suspect borers.
Insects suck plant juices and cause considerable damage.
Mites are quite small and can be easily discovered by shaking a branch over a white surface and watching the tiny red spots move. Use a few drops of Volck oil in your insecticide sprays to improve effectiveness. Be attentive to regular application of insecticides and mitecides. Apply Malathion , Sevin , Isotex for insects. Warm weather will also increase the productivity of various fungus infections.