According to the University of Florida, "magnolias encompass a group of about 80 species of trees and large shrubs." Magnolia shrubs are considered flowering shrubs or ornamental shrubs, because of the beautiful foliage of the plants. Magnolias are known for the showy, perfumed blossoms of various colors that appear in early spring each year. Trimming magnolia shrubs properly calls for pruning after flowering, since next years blossoms develop on this year's growth. Always use sharp pruning tools for trimming magnolia shrubbery.
Cut away any damaged, weak or diseased branches on the magnolia shrub. Disinfect your pruning tools after cutting off any diseased branches, and get rid of the cut branches. Clean tools with a mixture of water and bleach or alcohol; use nine parts water to one part bleach or alcohol.
Trim magnolia branches that are touching or crossing over the center of the shrub to increase air circulation and sunlight. Prune magnolia branches back to a lateral branch or bud to control overall size of the shrub. This is known as "heading back." Make the cuts at an angle, 1/4 inch above either a bud or branch.
Cut older branches back to the stem (or ground level) to thin out (or rejuvenate) magnolia shrubs. This will provide room for side branches on the stems or encourages new growth at the base of the magnolia shrub. Remove up to one-third of the oldest magnolia branches every year to maintain new growth each season.
Trim branches at various lengths to retain a natural appearance. Stand back often, and observe the overall shape of the magnolia shrub while pruning.