How to Grow Winter Gem Boxwood

Close up of Winter Gem Boxwood (Buxus microphylla japonica)

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Everyone knows boxwood by sight, if not by name. It is a common evergreen shrub found coast to coast, from the Gulf to the Upper Peninsula. A few varieties are especially preferred when looking for a type of hardy shrub to plant in a cold climate. A great choice is Winter Gem Boxwood (Buxus sinica var. insularis ‘Winter Gem’).

This dwarf-variety boxwood cultivar was introduced in 1982 at a nursery in New Jersey. It was selected especially for its cold weather hardiness, ultra-shiny dark green leaves, and lime green new growth.

New growth can be encouraged with yearly pruning in the spring. The foliage will seem to grow thicker whenever it is pruned.  ‘Winter Gem’ shines brightest when used formally in straight lines, as patterns as a hedge, or when shaped in a ball or square. It can also, however, hold its own in a landscape without trimming and its compact growth habit makes it an ideal choice for landscapes with limited space.

If you are shopping for Winter Gem Boxwood and cannot find a plant named Buxus sinica var. insularis ‘Winter Gem’, do not worry. In commerce, the shrubs are usually sold under the synonyms Buxus microphylla var. japonica ‘Winter Gem’ or Buxus microphylla var. koreana ‘Winter Gem.’ 

Botanical Name  Buxus sinica var. insularis ‘Winter Gem’ or Buxus microphylla japonica 'Winter Gem'
Common Name  Winter Gem Boxwood
Plant Type   Broadleaf evergreen
Mature Size  2 to 3 feet tall 2 to 3 feet wide
Sun Exposure  Full Sun
Soil Type  Moist, sandy loams with good drainage
Soil pH  Neutral
Bloom Time  April
Flower Color  Yellowish-Green
Hardiness Zones  5-9
Native Area   China, Japan and Korea
Toxicity  Yes

Winter Gem Boxwood Care

When people complain about boxwoods, it is often about needing to trim or prune the shrub. Most people want the beauty without the work. ‘Winter Gem’ does not offer maintenance-free plant ownership, unless there is a landscaper involved, but it can be low-maintenance in comparison to some other varieties.

Achieving a low privacy or border hedge with Winter Gem boxwoods can be done by spacing the shrub 12-24 inches apart when planting.

Light

‘Winter Gem’ Boxwood grows well in a wide range of light conditions, from full sun to partial shade.

Soil

The shrub will do okay in any soil that is not consistently wet. It prefers medium moisture in a well-drained soil that is sandy or loamy and with a neutral pH.

Water

Ensuring a newly planted Winter Gem boxwood receives one inch of water per week is essential until the plant is established. Minimal supplemental watering is necessary for established boxwood.

The ‘Winter Gem’ is somewhat drought-tolerant but not for extended periods. Mulching the beds under the shrubs is vital for moisture retention to guard the very shallow root system.

Temperature and Humidity

The ‘Winter Gem’ cultivar is ideal for people who have tried this species in areas where it suffers from burnt foliage due to frosty temperatures. The shrub is hardy down to temperatures as low as -20o Fahrenheit.  The perfect range for this shrub is anywhere in USDA Zones 5-9

Fertilizer

Every spring ‘Winter Gem’ will benefit from a shot of fertilizer. A suitable fertilizer for boxwood is a 10-6-4 mix, but it should only be applied if the beds under the shrub have been mulched. Applying fertilizer directly to the soil can harm the boxwood’s shallow roots. 

Pruning

The ‘Winter Gem’ boxwood will reach a height of three to five feet tall and have a spread of two to four feet naturally. This form can be desirable in its own right, but most gardeners prefer the formal look of trimmed boxwoods.

In colder climates pruning any boxwood should only be done in spring, never fall or winter. This will help achieve dense, compact growth.

Is Winter Gem Boxwood Toxic?

Winter Gem boxwood is toxic to dogs, cats, horses, and humans alike. Boxwood’s alkaline compounds cause acute toxicity known as boxwood poisoning. The compounds are so potent that they thwart even the hungriest of deer. 

It isn't going to be the best shrub for gardens with curious or greedy dogs or kids.

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