Allegheny Spurge (Pachysandra procumbens)

Allegheny-spurge (Pachysandra procumbens) is a flowering shrub often planted for ornamental ground cover. It spreads through rhizomes to form a dense carpet of leaves. This species has tiny, fragrant flowers that bloom in early spring.

I. Appearance and Characteristics 

Pachysandra procumbens, the Allegheny pachysandra or Allegheny spurge, is a flowering plant in the family Buxaceae, native to the southeast United States from West Virginia and Kentucky south to Florida, and west to Louisiana. The name Allegheny is sometimes spelled Alleghany.

Pachysandra procumbens is a shrubby ground cover which grows 8-12″ tall and spreads indefinitely by rhizomes to form a dense carpet of matte blue-green leaves mottled with purple and white. It is native to woodlands from North Carolina and Kentucky south to Florida and Texas. Ovate to suborbicular leaves (to 3″ long) are coarsely toothed at the apex but untoothed at the base. Leaves are typically deciduous in USDA Zones 5 and 6 but semi-evergreen to evergreen in Zones 7 to 9. Even where evergreen, the leaves may appear worn and tattered by mid winter. Tiny, fragrant, greenish white to white flowers bloom in terminal spikes (2-4″ long) in early spring before the new leaves arrive.

Genus name comes in reference to the male parts of the flower (thick stamens). Specific epithet from Latin means trailing in reference to the rhizomatous ground cover habit.

It spreads slowly to form a dense carpet 8-10” tall. Allegheny pachysandra performs well in a variety of soils from moist to dry and a range of soil pH as long as it is growing in partial to full shade. This woodland plant is also considered by many to be very deer and drought resistant.

II. How to Grow and Care

Light and Temperature

As the foliage of your Allegheny spurge can easily sun-bleach, it’s best if grown in dappled shade or full shade. This plant thrives in the shade of large trees, as sunlight filters through the canopy.

Temperature-wise, your Pachysandra procumbens prefers moderate climates. It grows well outdoors in zones 5 to 9. Even in moderate climates, it can begin to look a bit ragged in winter, but it recovers once warm weather returns.

Water and Humidity

Consistent medium moisture is good for Allegheny spurge It doesn’t require heavy watering, but it likes the soil to be moist at all times. An inch a week is likely all you’ll need to keep it happy.

If your Pachysandra procumbens plants are less than 2 years old, provide slightly more frequent watering in those initial years. This ensures they have the medium moisture they need to develop good foliage and form a dense carpet of matte blue green leaves.

Avoid overhead watering for Pachysandra procumbens. It is susceptible to leaf blight problems, and these can make them worse. When possible, use a soaker hose at the base of the plant for slow, gradual watering purposes.

Tolerant of southeastern US humidity, your Pachysandra procumbens plant can hold on in both dry and wet air conditions. It will accept dryer air, of course, but seems to thrive at about 50% humidity.

Soil

Your Allegheny spurge likes mildly acidic soil. Aim for a range which is 5.5-6.5 pH. If you’re not sure about your soil’s pH level, do a pH test before you plant. This gives you the ability to amend the soil before planting.

Organically-rich, well-draining soil is necessary for your Pachysandra procumbens plant to thrive and form a dense carpet. It should remain consistently moist for best development. Adding peat moss to your soil can help with moisture retention. Leaf mold is another great option, as is forest humus. Ensure excess water drains away easily.

Fertilizing

Fertilizing in the early spring is best for your Pachysandra procumbens. Most spurge species prefer a balanced fertilizer in the 10-10-10 or 12-12-12 range. Slow-release granular options are easiest to apply around your shrubby ground cover plants. Follow the manufacturer’s instructions for application.

Apply your fertilizer just as new growth begins to form. If necessary, you can apply a second dose in early summer. Usually it isn’t necessary to apply more fertilizer, as the plant is not a heavy feeder and its white flowers bloom either way. It will form a dense carpet through its rhizomatous ground cover habit regardless.

Pruning

As Pachysandra procumbens tend to stay around 6″ in height, you may not need to prune for height at all. If you’re using it as a dense carpet ground cover, this requires medium maintenance. You can set your lawnmower at 4″ and trim it down to a consistent size if you wish.

Slow-growing, this spurge doesn’t tend to be invasive like its relative Pachysandra terminalis. That one, the Japanese spurge, will rapidly invade other spaces. With your Alleghany spurge, you should find that a light edge trimming keeps it in check.

Propagation

Propagation from softwood cuttings is the most common method for spurges. They will readily form roots and create new plants via their rhizomatous ground cover habit.

Taking softwood cuttings from your Pachysandra procumbens plant is best in the early spring or late fall. Select newer growth before white flowers bloom, and cut off a piece which is at least 4″ long. Dip the end into rooting hormone and place into moistened potting soil. Keep the soil moist while roots form.

You can also divide the rhizome of your Pachysandra procumbens plant. Select a larger plant and cleanly cut through the center to divide it in half. A sterile, sharpened shovel blade works well for this purpose. You can then transplant one half while the other remains in place.

Pests and Diseases

• Common Pests 

Most pests tend to ignore Allegheny pachysandra. Those which do are opportunistic and are usually found on multiple plants at the same time.

Aphids are among these opportunistic pests. Treatment of these can be as simple as using a hard spray of water to rinse them off. Applying neem oil can keep these at bay.

Slugs are also quite common, as the spurge provides both shelter from the sun and food. Using an organic snail and slug bait provides the best protection for your plants.

Other pests which are less-common include spider mites and scale. Both are fairly rare on your spurge. Neem oil is a common preventative for these as well.

• Common Diseases

Volutella stem and leaf blight strikes multiple types of pachysandra. While pachysandra procumbens is more tolerant of it than other forms, it can still strike. This fungal blight causes cankers on erect stems. It also creates tan to brown spots on leaves which gradually increase in size. Over time, the leaf blight can completely cover the leaf surface.

Promoting good air circulation around your spurge plants helps reduce volutella blight. It is more common in damp or rainy conditions, so avoid overhead watering. As the weather warms up, it’s less prone to develop. Apply copper fungicide to prevent further spread, and trim off damaged material.

A variety of root or stem rots can also form in overly-moist conditions. These mainly develop in poorly-drained soil. Fungal causes include pythium, fusarium, or alternaria among others. For these, prevention is better than trying to cure. Ensure you have well-drained soils and that roots won’t be in standing water conditions.

• Growing Problems

Yellowing leaves can be a symptom of one of two major problems for Pachysandra procumbens.

Soil which is too alkaline can cause this issue. Pachysandra procumbens plants prefer a slightly-acidic soil, and if the pH is too high, they won’t thrive. They can develop pale green or yellowish-looking leaves or be stunted in growth. Raising the acidity of the soil can help with this.

The other problem comes from too much sunlight. Full sun conditions can cause the leaves of your plant to bleach. Yellow-green leaves are common in this situation. They may appear burned or become brittle. Ensure your plants are in partial to full shade.

Multicolor leaves are not uncommon on a dense carpet of Allegheny spurge. As seasons change, you may notice your pachysandra developing silvery or whitish leaf patterns. This is not harmful to your plant and, in fact, is sometimes referred to as the plant “opening its windows to let in the light”. It’s particularly common in autumn when the days are growing shorter.

III. Uses and Benefits 

Allegheny spurge is popular ground cover for a variety of shady locations in the landscape including areas under trees, foundations, around shrubs or along walkways.