Mistakes Everyone Makes When Growing Boxwood (And How To Fix Common Issues)

Many home gardeners choose to plant boxwoods in their yards. Caring for a boxwood shrub isn't rocket science, and these glossy evergreens can provide easy visual appeal to your space. There are also lots of ways you can use boxwood plants to add privacy to your backyard and the shrubs are deer-resistant. But, if you're thinking about planting boxwoods, don't assume that because these attractive bushes are generally easy to care for, you are guaranteed success.

Home gardeners can make several mistakes when growing this hardy plant. With the wrong treatment, your boxwoods may not grow to their potential, be slow to establish, become infested, diseased, or even die. Learning about what you shouldn't do when growing boxwoods can help you protect your plants from a tragedy and ensure lush green growth every season. Below, we'll share how you can head off mistakes centering around where to plant the shrubs, watering, pruning, and protecting them against environmental and pest pressure.

If you don't pay attention to the composition and pH of the soil where you plant your boxwoods, you might be setting them up for failure. Soil that doesn't drain well and stays continually damp can threaten the health of the plants. If the roots remain wet for too long, they may start to rot. Similarly, if the soil's pH is too high or low (boxwoods prefer their pH to be close to neutral), the plants won't grow to their full potential and may be more likely to develop issues.

To avoid these potential problems, start by choosing a location with well-draining soil. Avoid any areas of the yard where water pools or collects, such as near your downspouts. Once you've determined the ideal location, measure the pH of your soil. A pH meter, such as the Sonkir Soil Test Meter can help you assess the current level. The pH should be between 6.8 and 7.5, so if it is higher or lower than this you'll need to make adjustments. Dolomitic lime can be added to increase the pH level, while iron sulfate, peat moss, or acidifying nitrogen fertilizers can help make your soil more acidic.

One mistake some people make when planting boxwoods is putting them in the ground at the wrong time of the year. It's easy to assume that since they're relatively hardy, these shrubs can be planted during any season. This is not the case however, and planting boxwoods at the wrong time can make it more difficult for them to develop a resilient root system. Do not plant boxwoods during the summer or winter. The temperature extremes during both of these seasons will threaten the plants' ability to form strong roots.

Instead, plant them in mid-spring or early fall. During these times, more specifically around April or September, the plants will have an easier time setting down a robust root system. Certain boxwoods (especially dwarf species) are relatively slow-growing, so you don't want to stall root development by planting at the wrong time of year. 

Beyond considering the soil's composition and pH levels, there is something else you'll want to pay attention to when deciding where to plant your boxwoods. These shrubs may be able to grow in full sun, but are less likely to thrive than if they are placed in a partially-shaded area of the yard. Their leaves may become scalded from the hot summer sun and they also need some shade in the winter. During the winter, their leaves can turn orange if they are placed in a spot that gets full sun.

So, when deciding where to plant your boxwood, look for a part of your yard that is shaded for around 20% of the day. This will provide them with some reprieve from the hot summer days and protect their leaves from foliage burn during the winter. If possible, place them in an area that will also lessen the blow (literally) of cold winter winds. At the same time, be careful to avoid positioning your boxwoods in an area without any air circulation whatsoever, as some air movement is necessary to ward off fungal diseases.

Watering mistakes are common with boxwood and can threaten the health of your plants. If your boxwood shrubs don't get sufficient amounts of water, their root systems won't develop properly and the plant will enter a state of stress. Besides not delivering the nutrients the plants need, a poorly developed root system can also prevent the boxwoods from securely anchoring into the soil and may leave them open to more stress or during times of drought.

If your area gets at least an inch of rainfall each week, then you won't need to worry about your boxwoods. But during weeks without adequate rainfall, you'll want to be sure to water the plants to keep them hydrated and ensure their root systems develop and strengthen. When watering, avoid doing so from overhead. Leaving the foliage wet can increase the risk of fungal diseases. Instead, water from the base of the plant to keep the soil moist. Newer plants can also benefit from watering during the winter, especially before the weather is expected to dip to very low temperatures. This can help protect them from losing too much water.

After planting your boxwood, you mustn't overlook the importance of mulching around its base. Failing to apply mulch can cause the soil to dry out too much, preventing the roots from being able to suck up enough water. Mulch can also act as an insulator, protecting roots from temperature extremes. But, there are two common mulching mistakes you could make with a boxwood: First, laying mulch right up to the base of the plant. This can make conditions too damp along the trunk, increasing the chances of a pest infestation. Second, too thick a layer of mulch may also cause the plant to send off roots above the surface of the ground, which can be detrimental to the overall health of the plant.

The best thing to do to support the health of your boxwood is to lay mulch after planting. Aim to add a layer that is about 1 inch thick, as this will help retain moisture in the soil without suffocating the roots. To continue helping your boxwood plants along, replace old mulch each spring. Before adding fresh mulch, water the soil to dampen it. Also, avoid mulches that will create an impenetrable mat that prevents water and air from reaching the soil, such as grass clippings (which tend to compress, mat, and clump). Decomposed bark chips or compost are both good options. 

If you prune boxwood during the late spring, the summer, or early fall, the new growth the plant puts off may be subjected to harsh winter temperatures before it has grown and strengthened sufficiently to survive. Instead, boxwood should be pruned later in the fall, during the early winter, or early in the spring. When pruned during late fall or early winter, the external conditions won't be right for the plant to send out new shoots. When pruned in the early spring, if new shoots emerge, they'll have more time to mature before the following winter when the temperatures drop.

Proper boxwood care also includes thinning and shearing. While these may be confused with pruning, they are actually different things. Shearing is the process of making changes to the shape of the shrub by cutting more substantial portions of the branches back. June is the ideal time to shear a boxwood, but definitely do not try to shear your plants beyond early August. Shearing too late can increase the chances that the new growth will not be ready to survive the cold winter temperatures.

Thinning is precisely what it sounds like — removing some growth around the outer edges to make the plant less dense. This helps ensure more sunlight is able to reach all of the branches and encourage healthy growth. Thinning can be done throughout the year, as long as extreme temperatures are not predicted. 

Failing to protect your boxwood plants over the winter can threaten their health. The cold temperatures and harsh winds can dry the plants out, and the frozen ground will prevent moisture uptake. If the sun beats down on the already dehydrated shrubs, the bark may crack, especially if the daytime temperatures have been significantly warmer than those at night. As mentioned earlier, excessive sun exposure during the colder winter months can cause leaf reddening, and if combined with dry conditions, bronzing. Bronzing on its own is unlikely to harm the plant, and the leaves should return to a lush green color after winter has passed, but in severe cases where boxwood plants experience too much sun, wind, and dehydration, leaves can dry out entirely, turning a light straw color, and whole branches may die back. 

To avoid — or at least minimize — these problems, take measures to protect your boxwoods over the winter. Besides choosing a partially shaded area that will offer some reprieve from the cold winter winds, promptly clear snow from the shrubs. You may also want to consider setting up a windbreak to help prevent harsh winds from drying the plants out too much. A large piece of burlap fabric attached to a few stakes in the ground is an effective way to shield the plants. Using plant-safe ice melts for your property is also advised, and if your boxwoods are near public roadways where salt is applied, try to place the windbreak where it will offer some protection from salt spray. During warm stretches in the winter months when the ground isn't frozen solid, be sure to water your plants to help them regain some of the moisture that they have lost.

There are a few pests that are likely to be problematic for boxwoods. These pests often cause damage to the leaves, potentially causing them to color, wilt, cup, or drop sooner than they should. Some may also cause more serious issues, such as stunting the growth of the twigs or even potentially killing the entire shrub.

While insecticides can be used to kill off large infestations, trying other control or prevention methods first is generally recommended. Let's look at two common pests that threaten boxwoods and what you can do to keep them from becoming a problem. The first is one of the most serious, the boxwood leafminer. Female leafminer flies lay their eggs on the leaves. After the larvae overwinter and adults emerge, they eat the leaves, causing them to change shape, become blistered or discolor, or even drop from the shrub. If enough pests are present, the plant may even die. To prevent leafminers from becoming a problem, try pruning about one-third of the shrub back, getting rid of the infested leaves and stems. You can also consider using malathion or other contact insecticides, but these will not be as effective if the adults have already started laying eggs.

Boxwood mites are another pest to be on the lookout for. The small mites, which are related to spiders, are only about 0.5 millimeters in length. The eggs are laid on the leaves and overwinter there before hatching in the spring. Once they hatch, the mites suck the sap out of the leaves, simultaneously injecting a toxin. The toxin they inject leads to the leaves being covered with very small yellow scratches, known as stippling. Encouraging natural predator bugs to visit your yard can help prevent boxwood mites from causing serious damage to your plants. Ladybugs and predatory mites are two potential options to introduce. One of the best ways to bring good insects into your garden is by growing a variety of plants that will produce a steady supply of blooms throughout the year. You may also consider spraying the mites with blasts of water or horticultural oil.

There are also several diseases that can pose a problem to boxwoods. Some of these include root rot, stem blight, macrophoma leaf spot, and boxwood blight. These diseases can cause a range of problems from rotting roots, discolored leaves, cankers on the stems, spotted leaves, and even death of the entire plant.

Root rot is a common problem with boxwood. As discussed earlier, soil conditions and watering procedures can be key in preventing it — always choose well-draining soils and avoid overwatering the plants. Boxwood blight, which is caused by the Cylindrocladium pseudonaviculatum fungus, starts by spotting the leaves. Soon, the leaves develop dark spots, turn brown, and drop from the plant. The shrubs also develop black cankers along its green stems. If your boxwood contracts this disease, remove dead branches as soon as possible, destroy impacted leaves each year, remove old leaf debris and mulch from beneath the bushes, and consider applying a fungicide (particularly a chlorothalonil-based product). Apply fresh mulch to help prevent spores from the soil reaching the leaves of your boxwood. 

Macrophoma leaf spot is another disease to be on the lookout for. It is caused by Dothiorella candollei, a parasitic fungus. The disease leaves several raised black spots all over the leaves, which will either be the color of straw or dead. If you notice signs of macrophoma leaf spot, prune back any infected portions and destroy the pruned plant matter (do not compost it). Keeping up with a regular schedule of thinning the plant can also help prevent future infections.

Just as we need the proper nutrients to remain healthy, the same is true for boxwoods. If they aren't getting the right nutrients, then you can't expect them to grow and thrive as you would desire. Unlike many other shrubs and ornamental plants, which thrive on a steady fertilization schedule, there isn't a routine feeding regime for boxwoods. Short of testing the soil, examining your plants for signs of nutrient deficiencies is the best way to gauge whether boxwoods need a feed. One warning sign to look for is yellow leaves and tips. This can be a sign that the shrub isn't getting sufficient amounts of nitrogen and magnesium, particularly if you notice yellowing of the older, more interior leaves, or thinning, shrunken, or falling leaves. When you notice such signs, then you'll want to add a slow-release, nitrogen-rich, 10-6-4 fertilizer. The best time to fertilize boxwoods is in the fall as this encourages root development.

If the pH of your soil is off, this can cause nutrient lockout, as well as other problems. For example, if it is too low, the leaves of your boxwoods may become overly pale or otherwise discolored. If you suspect the pH isn't ideal — even if you initially tested it before planting your boxwood, use a soil meter, or send in another sample, to confirm the current level and take steps to raise (or lower) it as needed.

While boxwoods can survive in a container, you shouldn't assume that just any planter will do. First, if you choose a container that is too narrow, the shrub's wider root system won't have enough space to spread out. This can impact its ability to take up water and nutrients. Container color can also matter. The sun can make planters that are black or another dark color overly hot in either the summer or the winter. This can stress out boxwoods, interfere with their roots' ability to function properly, and potentially kill the entire plant.

Potted boxwoods can also be more susceptible to overly hot or cold weather conditions. Their roots won't be as insulated, which can threaten their health. Ensuring that your shrubs are mulched — but not so deeply that it covers parts of the plant's stem  — is important, along with well-timed watering. Be sure to supply them with plenty of water before winter sets in, and again during warmer periods of the winter when the soil isn't frozen. Lastly, place your potted boxwood in a protected area.