What Kind of Fertilizer

• Phosphorous is like baby food for young plants.Jupiterimages/Photos.com/Getty Images
  
  Newly planted arborvitae have different fertilizer needs than established arborvitae. For new plantings, use a fertilizer higher in phosphorous to promote good root development. The middle number on the fertilizer bag represents the percentage of phosphorous by volume. For established arborvitae use a fertilizer higher in nitrogen (the first number on the bag) such as a 12-6-3 or a 16-6-6 to encourage and promote healthy foliage and branches.
  
  

How Much Fertilizer

• Calculate fertilizer rates based on the first number on a bag of fertilizer.Warrick Page/Getty Images News/Getty Images
  
  How much fertilizer to use depends on the size of your arborvitae. In general, if fertilizing multiple arborvitaes, use about 2 to 4 lbs. of a nitrogen fertilizer per 100 square feet of root area. If fertilizing individual trees, fertilize at a rate of 1/3 lb. of nitrogen per foot of tree height. You also can calculate how much to use by measuring the trunk diameter at a height of 4 1/2 feet from the ground. Use 1 lb. of nitrogen fertilizer per inch of trunk width.
  
  

How to Fertilize

• For mature arborvitae, holes 12 to 15 inches in depth can be dug to apply fertilizer.Hemera Technologies/AbleStock.com/Getty Images
  
  Fertilize arborvitae by either a surface application or below-ground applications. For surface applications, evenly broadcast the fertilizer around the base of the tree, using caution to ensure that none gets on the foliage as it can burn. Make below-ground applications by applying the fertilizer and working it into the soil; nutrients are delivered to the roots quicker than with a surface application. Another method is to bore holes around the drip line of the arborvitae and evenly distribute the appropriate amount of fertilizer.
  
  

Other Considerations

• A fence can be constructed from burlap and stakes to protect your arborvitae.Jupiterimages/Photos.com/Getty Images
  
  Keeping your arborvitae otherwise healthy can eliminate the need for fertilizers. When selecting a site for new plantings, make sure it receives partial to full sun and that the soil is moist but well-drained. Arborvitae can be planted in a raised mound in the absence of soils with good drainage. For established plantings, ensure that foliage does not dry out in winter time by providing protection from the desiccating winds.