Good Fertilizer Formula for Young Arborvitae

pH Adjustment

• While arborvitae can tolerate a range of acidic and alkaline soils, they prefer slightly acidic to neutral soil. To improve your soil's pH before planting the tree, aim for a level of between 6.0 and 7.0. A soil test kit or pH meter will determine your soil's current pH, and consequently how many points you will need to raise or lower the pH. For acidic soil, the formula for adjusting the soil is 5 pounds of limestone per 100 square feet to raise the pH by one point -- for example, from 5.0 to 6.0. If you have alkaline soil, a common formula is the application of 1.5 pounds of elemental sulfur per 100 square feet to lower the pH by one point. Although your young arborvitae won't take up 100 square feet, amending that amount of soil helps surround the tree with its preferred pH as it grows.

Planting Amendments

• In general, it's best not to fertilize your young arborvitae at the time of planting. If you provide a planting hole that is overly fertile, the tree's roots won't want to extend beyond those few feet into less enriched soil. One exception to this general advice applies to soil that is severely infertile or especially sandy or hard-packed. In these cases, the National Gardening Association recommends blending finished compost into the soil you've removed while digging the planting hole. Aim for a blend of 50 percent or less compost, with half or more the original soil.

Traditional Formula

• A slow-release, all-purpose plant food is the best choice for young arborvitae and other evergreen trees and shrubs. If the fertilizer is labeled with the ratio of nitrogen, phosphorus and potassium, choose a formula such as 15-5-5. In fact, any formula in which the ratio of nitrogen to the other two nutrients is about 3 to 1 to 1 is best. Otherwise, choose a plant food labeled as all-purpose, slow-release and suitable for trees and shrubs. Your application area is the ground under the tree's canopy, extending a few feet in all directions. Young arborvitae do not take up much room, so a 10-square-foot area is optimal. Unless the plant food says otherwise, use no more than 4.5 ounces to feed young arborvitae, and do so in early spring.

Organic Formula

• Compost is a simple, all-purpose material for fertilizing young arborvitae trees. Setting a 2- to 3-inch layer of finished compost from the base of the tree to about 1.5 times the canopy area will provide the nutrients it needs. For a more specific all-purpose organic fertilizer, blend three parts blood meal to one part bone meal and two parts greensand. To feed your young arborvitae, you will only need about 1/3 pound of this formula. As with a synthetic formula, applying organic compost or a blended formula is best undertaken in early spring.