There is no distinctive line that separates trees and shrubs. Some trees many only reach 15 feet in height, while many shrubs may reach up to 20 feet. Those shrubs may serve as small trees, particularly if lower branches are pruned back. Shrubs and trees are meant to occupy a permanent place in the garden or landscape, so meeting their nutritional requirements, by providing nutrient-rich soil and replenishing nutrients that have been used up is an important part of assuring that you will have strong, healthy plants for the duration of their lives.
Amending Soil When Planting
Planting trees and shrubs in amended soil is one way to give your new additions a good start. Add soil amendments to soil removed from planting holes before backfilling. Mix one shovelful of compost or other organic material to backfill soil, providing needed nutrients for your shrubs and trees to get a good foothold. This will also improve water retention of the backfill soil and create a transition zone between backfill and the soil contained in the root ball of balled and burlapped trees. Organic materials that can be used, other than compost include: peat moss; ground bark; and nitrogen-fortified sawdust.
Liquid Fertilizer for Seedlings
Seedlings should receive applications of diluted liquid fertilizers (about half strength), like compost or fish emulsion after each transplanting and once during the month between the first transplanting and the final transplanting.
Preparation for Bare Root Planting
Bare root plants should be soaked overnight to assure roots are fresh and plump before planting. Soaking in compost tea instead of plain water fills tree roots with needed nutrients, as well as moisture.
Replenish soil nutrients as they are used up. Young trees and shrubs should be fertilized at least once a year for several years after they are planted. Fertilize with top dressings of at least two inches of compost early in the spring to assure a good nitrogen supply to encourage a springtime growth surge and become established quickly. Fruit and nut trees may require continued fertilization annually, even after they have become established, to enhance productivity.
Weak, sparse or unusually pale trees and shrubs may require applications of supplemental nutrients. Trees and shrubs displaying these symptoms may be nitrogen deficient and would benefit from an application of nitrogen. Good sources of nitrogen include: bat guano; blood meal; fish meal; and soybean meal.
Other times supplemental feedings may be needed are following times of plant stress, severe insect or disease attacks, or tree damage that requires heavy pruning. At these times, an immediate nutrient boost can be given by administering compost tea as a foliar spray, allowing the nutrients to be absorbed directly through the foliage.
Fall applications of compost can be beneficial to trees and shrubs, especially in colder climates, but use caution not to make the application too early and promote new growth that would be cold-tender. It is better to make the application about a month before the expected flush of late winter or spring growth.