Tolerant, pretty wax myrtle (Myrica cerifera) doesn't need a lot of help growing well. At home in a wide range of environmental conditions, wax myrtle usually does better without fertilization. However, if your soil really is nutrient deficient, a fertilizer may help encourage growth on ailing wax myrtles.
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Aside from their evergreen leaves, wax myrtles are known for attractive whitish-gray bark and the silvery blue berries that coat the branches of female plants and help attract wildlife to the garden. At full size, they have a rounded canopy that can grow to heights and widths of 25 feet, but usually tops out closer to 10 or 20 feet. Many people like to grow wax myrtles near terraces or patios, where waving branches provide dappled shade and relief from hot days.
Wax myrtle is generally a tolerant, hardy plant that doesn't require a lot of encouragement to grow well and look attractive. Hardy in U.S. Department of Agriculture plant hardiness zones 7B through 11, they grow quite quickly, sometimes as much as 5 feet in the course of one growing season, and generally perform well in heat, cold, drought and other adverse conditions without help. Nevertheless, if you think your plant may need a jolt, feed it a low dose of shrub fertilizer like 12-4-8 while the plant is actively growing.
Dangers of Fertilization
Wax myrtle is not a tender plant, and has evolved to respond well to adverse environmental conditions without a lot of help. It is capable of fixing nitrogen, which means that its roots can manufacture this necessary nutrient for themselves. Overdosing it with fertilizer can have the effect of burning it rather than helping it, so before you use a fertilizer at all, make sure your soil is really nutrient deficient before applying. Resist the urge to add fertilizer late in the season, when the plant will not be able to make use of it and it could have adverse effects.
Wax myrtle has a wide range of tolerances, being native to both boggy wetlands and dry highlands. It will put up with sogginess and drought, but prefers a moderate amount of water, good drainage and acidic soil, if possible. Wax myrtles will grow in either partial shade or full sun and take pruning well. You can therefore grow them as shrubs, or prune them to encourage a tree form. They tolerate aerosol salinity well, so make good additions to seaside gardens.