Routine Care

Boxwood have always been popular for their low and easy maintenance.  However, to make a boxwood garden go from good to great, a few simple steps should be followed.

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• Slows weed growth and reduces erosion.

• Retains soil moisture and creates organic matter.

• Moderates soil temperature.

• Lessens diseases including Boxwood Blight.

Mulching at the time of planting and periodically thereafter is beneficial in many ways and is highly recommended.

In mature boxwood plantings, add no more than a half inch per year. Be sure mulch is aged or decomposing. See discussion under Boxwood Planting & Site Selection.

In addition to other benefits of mulch, recent research has also shed light that mulching can be an effective tool to aid in disease management. Earlier this year, Virginia Tech published data from a two-year study showing that mulching can be a great tool to help prevent Boxwood Blight. Results of the experiment showed mulching reduced the number of Boxwood Blight lesions by up to 97%! Even the scientists working on the project were amazed by the unbelievable difference that mulch made. Although for a long time it was thought that mulching boxwood was a bad idea, this study shows that it can be an exceptionally effective tool for Boxwood Blight control. Below you will find a downloadable PDF of these findings. Saunders Brothers, Inc. worked with Chuan Hong and his team at Virginia Tech to provide plant material for the experiment.

• Clean tools properly before and after pruning.

• Prune in late winter to early spring before spring flush while diseases are less active.

• Use pruning techniques that promote good air flow.

• Note that pruning techniques are different for each cultivar.

Proper pruning techniques are crucial to long-term success with boxwood. Pruning techniques differ with each cultivar of boxwood. It is important to choose the correct cultivar for the desired use and location to avoid the need for excessive pruning.

Proper sanitation is important when pruning. All tools should be properly cleaned with alcohol, bleach, Lysol® or some other disinfecting solution before and after working with boxwood to lessen the possibility of spreading diseases. Do not allow tools from other nurseries or gardens to be used on your boxwood, as they could spread diseases.

The best time to prune boxwood is in the late winter to early spring, before the plant breaks dormancy. This is typically February or March in central Virginia. Late winter/early spring pruning stimulates a strong, uniform spring flush. It also is a good time to prune because diseases like Boxwood Blight tend to be much less active in cold temperatures. Some gardeners also like to prune in late spring, after the flush, to achieve a more manicured shape in formal gardens. Mid-summer and early fall pruning stimulate late fall growth that may be burned by frost or early winter freezes. Early winter pruning, while not detrimental, leaves pruning scars on the leaves until the spring flush is initiated. Many gardeners choose to thin or pluck Buxus sempervirens ‘Suffruticosa’ (English boxwood) and Buxus sempervirens (American boxwood) in late November and December in order to have boxwood greens for holiday decorating. This is a very common practice and one that is helpful to the plant. Once again, take care to clean tools when pruning to avoid spreading diseases.

In general, any pruning that increases the airflow in a boxwood is advantageous. Cultivars that are more dwarf or have very tight habits benefit from annual thinning to increase air flow and sunlight penetration into the interior of the plant. Thinning is typically done by reaching into the plant and breaking off or cutting out branches with hand pruners. These branches can be 6-10 inches long on larger cultivars, or only a couple of inches on a dwarf cultivar. This will leave pockets or holes in the plant for air and sunlight penetration. Using hand pruners will result in a cleaner cut and lessens the possibilities of disease introduction. Any cultivars that are sheared regularly will benefit from thinning to lessen disease susceptibility.

The above images from left to right show a Buxus semervirens ‘Dee Runk’ before, during, and after its annual spring pruning.

It is common to see boxwood that have overgrown their allotted space and need extreme pruning to get them back to proper size. More vigorous cultivars are generally responsive to more radical pruning techniques. To do this, in the early spring use loppers or shears to drastically reduce overall plant size on vigorous plants, taking care to leave about one-half of the foliage undisturbed. The undisturbed foliage will produce the energy the plant needs to recover. If properly thinned so that light penetrates into the interior, the plant will develop new foliage along the bare stems so that in the second early spring, the plant can be pruned back to its desired size. It is important to do this over two seasons to not stress the plant too much.

The above technique works well to reduce the size of Buxus sempervirens ‘Suffruticosa’ (English boxwood). You should never use shears on Buxus sempervirens ‘Suffruticosa’. Using shears increases the density of the canopy of the plant and shatters brittle limbs thus increasing the chance of disease. To minimize radical pruning, do not select large cultivars for applications where small cultivars would be more suitable.

Boxwood will occasionally send up a branch of foliage that is different from the rest of the plant; this is known as a “sport” or a “reversion.” This is most obvious on some of the dwarf cultivars including Buxus microphylla ‘Green Pillow’, Buxus microphylla ‘Grace H. Phillips’, Buxus microphylla  ‘Morris Dwarf’, and Buxus microphylla  ‘Morris Midget’. Remove the sport by cutting into the plant below the point where the sport appeared. Sports on plants do not hurt the plant, but they can be unsightly.

• Boxwood are drought tolerant once established.

• Initial watering at the time of planting is very important.

• For first 18 months after planting, monitor moisture and irrigate as needed.

• Irrigate established boxwood only during extreme droughts.

• Drip irrigation is best on any plantings. Avoid systems that repeatedly wet foliage.

• Over-watering causes problems.

It is very important that newly planted boxwood be watered thoroughly at the time of installation. For the next year or so, new boxwood should receive approximately one inch of precipitation or irrigation per week paying most attention to hot summer months or times of drought. The first year-and-a-half after planting are the most critical for irrigation. Typically, boxwood need little supplemental irrigation October through April. Always monitor soil moisture before irrigating. Boxwood will do best when they are watered thoroughly by wetting the root zone to a depth of 12 to 18 inches. The root zone should then be allowed to dry before the next application of water to encourage stronger root systems, as plants are forced to send roots in search of water. Timing of subsequent watering will be dependent on natural precipitation, weather, and soil conditions. Avoid allowing the plants to dry to the point of showing stress as they have difficulty recovering. 18 months after planting, boxwood require supplemental water only in times of extreme drought. One of the primary reasons people have planted boxwood for thousands of years is their drought tolerance.

Simple drip irrigation systems work exceptionally well for boxwood. They allow for slow application of water through the root zone area and penetrate deep into the soil. If only used during dry times, these systems tend to not over-water like a sprinkler system would.

Lawn irrigation systems intended to keep grass green should be designed and maintained to avoid daily application of water onto the foliage of nearby boxwood. Continual wet foliage on a boxwood creates an ideal environment for diseases to flourish, particularly Boxwood Blight.  Watering that keeps the root zone wet all the time creates a perfect environment for Phytophthora, or root rot, which is deadly to boxwood.  Some cultivars, especially Buxus sempervirens (American), ‘Suffruticosa’ (English), ‘Jensen’, ‘Elegantissima’, ‘Vardar Valley’, ‘Justin Brouwers’, and other sempervirens cultivars, are especially susceptible to root rot resulting from continuously wet or soggy soil conditions or poorly-drained soils. Remember, roots need air as well as water. In periods of extreme cold, it is important to be sure newly planted or transplanted boxwood are thoroughly watered prior to the ground freezing. Filling the air space around the root system with water helps to insulate the plant. 

• Use soil tests to maintain a pH of 6.5-7.0.

• Apply fertilizer in late fall or early spring on top of the mulch.

• Avoid summer and early fall fertilization to prevent frost or freeze damage.

• If fertilizer is needed, use a balanced fertilizer or aged manure.

Although boxwood typically do not need a lot of fertilizer, soil tests should be used to determine fertilizer needs as well as the pH of your soil. Boxwood thrive when the pH of a soil is between 6.5 and 7.0, any pH below about 5.8 can cause problems. The optimal time to fertilize is in late fall or early spring. Boxwood roots grow the most in late fall, winter, and early spring, when soil temperatures are more moderate. Late summer and early fall fertilization may cause a plant to initiate new growth that may be burned with early fall frosts and freezes.

Always place the fertilizer near the drip line of the plant and never place it under the mulch. Boxwood typically have feeder roots just under the soil surface, so placing fertilizer directly on those roots can cause damage to the plant. Do not use fertilizers formulated for acid-loving plants like azaleas or rhododendrons as they tend to drive down pH. Saunders Brothers, Inc. in central Virginia uses aged poultry manure in low rates both at the time of planting and as needed thereafter with great success.

• Transplanting Is optimal in the fall.

• Dig a hole 2 to 3 times wider than deep to fit the root ball.

• Monitor moisture carefully for 12-18 months.

Boxwood can be transplanted from one location to another. Take care when transplanting boxwood, considering proper timing and procedures.

The best time to transplant boxwood is in the fall. In your area, choose a time in the fall when summer heat has begun to subside, and more frequent rain and cooler temperatures have arrived. Avoid waiting until severe cold sets in. Some gardeners have success transplanting during mild winters, particularly in Plant Hardiness Zones 7-9. Proper timing will allow for maximum root growth when moisture is typically more abundant and in turn better prepares the plant for dry summers. The root ball should be dug as wide as the canopy of the plant (at a minimum). The root ball size will vary but a rule of thumb should be for every 2-3 feet in width, the depth should be 1 to 1 ½ feet. Boxwood have shallow roots thus more focus should be on root ball width than depth.

Do not leave the boxwood above ground for a long period of time especially in times of extreme heat or cold and do not allow the root ball to dry out. Never move boxwood during the stress of summer heat or severe drought. Many gardeners have greater success when they thoroughly water the plant they are moving prior to any digging to lessen the stress on it. Immediately after transplanting, water thoroughly again and continue to monitor moisture for 18 months or so until the plant is re-established. Never allow the plant to dry to the point of showing stress. Once drought-stressed, boxwood seldom recover completely.

Avoid repeated cultivating or tilling near the roots of boxwood. Boxwood roots are shallow and widely spread. Cultivating near the drip line of the plant creates problems in boxwood. This is especially evident when boxwood are used as edging in a bed. For example, if one side of the plant is restricted in horizontal root growth by a “hard edge” like a sidewalk or manufactured edging, and the opposite side is tilled 1-2 times a year for planting annuals, severing the roots repeatedly will cause long term problems and potentially kill the plant.  If possible, avoid cultivation within 1-2’ of a boxwood hedge.

• Avoid summer and early fall fertilization and pruning.

• Spring frosts/freezes can burn new growth. However, in most cases, new buds will quickly develop and cover any damaged foliage.  

The terminology frost damage usually refers to a rather mild frosting of plants in the fall or spring, generally resulting in light die-back in the tops of boxwood. Freeze damage occurs at the same time but describes more severe damage as a result of colder temperatures or more prolonged cold temperatures. In the mid-Atlantic area of the United States, the damage from these weather events usually occur in the fall from October through early November, or in the spring from late March through early May. The resulting damage is a “burning” of the most tender foliage, usually the tips of the newest growth, of the boxwood. The damage occurs when the temperature gets below 30 degrees Fahrenheit, with the worst damage occurring during a freeze event when the temperatures get into the low to mid 20’s. An extreme freeze event, with temperatures in the low 20’s in the fall or spring, can cause bark splitting, with resulting dead limbs or perhaps even the death of the entire plant.

In the fall, the extent of the damage of a frost/freeze event is related to the temperatures leading up to the cold temperatures, with the worst damage occurring with a very warm fall followed quickly by a severe and early frost or freeze.

To lessen fall frost/freeze damage, avoid summer and early fall applications of fertilizer that could induce a late fall push of growth that could be burned.  Also avoid late summer pruning which can induce fall flushes that are typically tender and easily burned.  If a fall frost or freeze event damages any foliage, avoid heavy pruning.  Simply cut off the unsightly damaged foliage.  Heavy pruning in the fall invigorates the plant just before the coldest part of winter, setting the boxwood up for severe damage which the plant might not recover from.

In the spring, the extent of the damage is related to the development of the new growth in the boxwood, with the worst damage occurring with a very early and warm spring fully pushing out the new growth of the boxwood, followed by an abnormally cold night.

Spring frost/freeze damage is difficult to prepare for or to prevent.  After the cold event, the only pruning that is typically needed is general shaping as sometimes the frost affects the plant inconsistently. The good news is that new spring growth quickly covers any spring frost damage. 

• Before extreme cold, water newly planted boxwood before soil freezes.

• Full sun exposures greatly increase likelihood any type of cold damage.

• Allow snow to melt naturally or very carefully remove.

Winter cold injury is usually associated with extreme cold temperatures in the mid-winter months of December, January, and February.  One of the first steps when selecting a boxwood is to be sure that the cultivar you select will survive the winter in your geographic area.  Most boxwood cultivars are given a USDA temperature zone by breeders and growers with experience in colder regions.  Pay close attention to your cultivar’s designated Cold Hardiness Zone and be careful to not plant a cultivar that is not suited to your area.

Even the most cold-hardy boxwood sometimes either die back or completely die due to extreme temperatures in the winter.  The worst damage occurs when there is a dry spell with minimum moisture leading up to extreme winter temperatures with no snow.  Indeed, snow cover on boxwood tend to insulate the plant from extreme cold, so snow is considered to be very beneficial during very cold temperatures.

In snowy conditions, it is best to leave the plants alone and let the snow melt on its own. However, in extreme cases when there is chance of breakage, gradually remove the snow by gently brushing the limbs with a broom. Remember: if the branches are frozen, beating them or any quick movement of the branch will cause damage to the limb or bark and will encourage disease. Some of the microphylla cultivars are more rigid and will hold snow with minimal to no damage. In heavy ice storms, leave the ice on the plants to melt naturally.

Another type of winter damage is foliage bronzing which can be attributed to sun exposure and cultivar selection. Direct sun in the winter (especially from the southwest) will tend to bronze some cultivars more than others. Bronzed leaves typically begin greening up in the spring as temperatures begin to rise and as new foliage covers them. Intense sun on shade-loving cultivars will cause bronzing that does not recover quickly in spring and can cause long-term problems. If you want to minimize bronzing, take care to avoid planting in sunny southwest exposures and consider your variety. Good choices include NewGen Independence®,  ‘Green Beauty’, ‘Jim Stauffer’, ‘Dee Runk’, ‘Vardar Valley’, ‘Fastigiata’, ‘Justin Brouwers’, sempervirens (American), and ‘Little Missy’. Cultivars like ‘Wintergreen’, ‘Winter Gem’, NewGen Freedom®’ and the “Green Series” (‘Green Velvet’, ‘Green Mountain’, ‘Green Mound’, ‘Green Gem’), as well as some of the dwarf cultivars of boxwood tend to bronze in winter sun. Refer to the cultivar section of the Boxwood Guide for more information.

Bark splitting is perhaps the most severe damage from either fall, winter, or spring cold temperatures.  Bark splitting is common with extreme temperatures during any season.  Oftentimes, the bark splitting is not evident until a month or two after the cold event.  Most of the plant, or perhaps a few limbs of a plant begin to turn an off-color.  With time, the entire limb progressively turns to an off-green and then a straw color.  With careful inspection, if you trace the limb to where the off-color foliage starts, you can see that the bark is “lifted” from the cambium at a particular point on the limb.  All growth that is above the bark splitting will die.  Depending upon the extent of the injury, the plant usually will recover.  The best solution to bark splitting is to simply cut off the dead growth and hope the plant recovers.  It is not uncommon for bark splitting to kill newly planted boxwood that are 12” or smaller.  Bark splitting is most often seen on boxwood under three years of age, plants that are very vigorously growing, and plants that have just experienced an extreme cold event.

The best solution for fall or spring frost/freeze damage or for midwinter cold injury is to plant your boxwood where they have protection.  Forms of protection can be either evergreen or deciduous trees towering over the plants, a house or other building, or any type of woods or other ornamental plants near your boxwood.  The most effective protection is high shade on the south and west side that shields the boxwood from the late afternoon sun.  This over-story of trees that protects boxwood are often a hidden secret in the success of a garden.

Another source of protection used often in commercial nurseries are overhead sprinklers used in an early fall or late spring cold event.  When the temperature go below 32 degrees F, sprinklers are turned on and ice freezes on the plant leaves.  The freezing water releases heat, and will oftentimes protect the boxwood very well into the mid 20’s.

Once the temperatures get into the upper teens or low 20’s, the sprinklers freeze up and this type of protection is no longer effective.  It is therefore recommended that nurseries monitor the weather forecast closely in order to properly make decisions in advance of a cold weather event.

Boxwood are an excellent choice for use in a container. When planting in a container, take care to select a container that is larger than the root ball of your chosen plant. If you allow space for the roots to grow, the boxwood will have a longer life in the container. Use a potting media to fill around the root ball. Be sure the container has drainage holes in the bottom.

After several years it may be necessary to remove the plant from the pot to re-invigorate it. Cut and loosen the roots and replace much of the soil in order to stimulate new root growth on the plant before placing it in the same or a larger container. When the root growth is limited, a plant typically will begin to deteriorate. Fertilize lightly annually with well-balanced fertilizer that does not drive down the soil pH (See Fertilization).

Although boxwood are more drought-tolerant than many plants, be sure to provide adequate water throughout the entire year, including the winter. In winter it is very important that the plant is well watered before extreme cold spells. Filling the air space in the root system with water helps to insulate the plant. In summer, water as needed. Regularly monitor water and keep roots moist but not wet.