Specially Formulated Shrub and Tree Fertilizers will contain what is called a "micro-nutrient package". This package may contain other nutrients that shrubs and trees appreciate, such as iron, sulphur, manganese, zinc and others. Other fillers might be included to help apply the nutrients evenly over an area.

Experienced gardeners, nurseryman and professional landscapers may recognize a plants need for fertilizer, or the need for a particular nutrient, by simply looking at the foliage. For example, if the foliage of a plant is turning light green or yellow, this might indicate a nitrogen or iron deficiency, or perhaps theres too much moisture around the roots. Similarly, purple foliage (on an otherwise green plant) might be a sign of phosphorus deficiency. The only true way to determine what fertilizer or nutrients a plant need is through having a soil test done. Most states, and many counties offer soil tests through their Cooperative Extension Service at no charge (or for a small fee). A soil test will indicate what nutrients are need, and ensures that the correct amount and type of fertilizer will be used on your plants.

In the absence of a soil test, you can assume that most plants in a landscape setting require more nitrogen than they get from natural sources. One reason is that the leaves that have fallen from the plant that could have put nutrients back into the soil are often raked and removed. Most ornamental shrubs and trees planted in landscapes are grown in nurseries under ideal conditions. After having been planted in the natural soil conditions of your landscape, plants and trees may require some additional nutirents to help them adapt.