How To Care For Mock Orange: Growing Philadelphus Lewisii

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In 1806, the famous Lewis and Clark expedition was in full swing, and Meriwether Lewis was documenting a lot of new species along the way.

One of these was Philadelphus lewisii (Fil-uh-DEL-fuss, Lew-ISS-ee-eye), a compact shrub with a wide range but tended to be sparse within that range.

Flowering mock orange (Philadelphus lewisii)Pin

This perennial member of the Hydrangeaceae family is best known as mock orange and is the state flower of Idaho.

Other common names include:

  • Gordon’s mock orange
  • Indian arrowwood
  • Lewis’ mock-orange
  • Syringa
  • Wild mock orange

Natively, it can be found in California, Idaho, Montana, Oregon, Washington, and British Columbia.

Mock Orange Care

Size and Growth

This rounded, multi-stemmed ornamental shrub can grow to an impressive 10′ feet tall and 6′ feet wide, although it tends to be a much smaller 4′ to 6′ feet tall when grown in a container.

Young stems are reddish-brown but will fade to grey as they age, making the bark flaky.

As the plant enters dormancy, its light green foliage turns yellow in the fall.

They have a rough texture and can be either serrated or smooth-edged.

Flowering and Fragrance

During their bloom time from May to July, mock orange becomes covered in white, four-petaled flowers with a bright yellow center filled with tall sepals.

The white flowers tend to be grouped in clusters of 2 to 15 double flowers each.

When the petals fade and fall, the sepals will be left behind, extending the display.

Fertilized flowers will give way to small capsules with woody wings and numerous tiny seeds.

But what makes the white blooms interesting isn’t the sepals or their numbers but the scent.

The fragrant flowers give off a heady, sweet scent similar to orange blossoms but with a hint of pineapple. The blooms also look similar to citrus flowers, hence the nickname.

Light and Temperature

Mock orange shrubs love sunlight but need it in moderation.

Immature plants are more sensitive to direct sun, although they become a lot more durable as they age.

For this reason, a spot that can receive full sun in the morning or evening with some light to partial shade in the afternoon will often work best.

Syringa is surprisingly adaptable to various conditions and can handle temperatures as low as -10° degrees Fahrenheit.

However, it’s not as fond of especially hot weather and is thus best grown outdoors in USDA hardiness zones 4 to 8.

Watering and Feeding

This plant can survive brief periods of drought once established and can often survive on rainfall alone.

For both potted and garden specimens, you will want to water the immature plant when the soil feels dry 1″ inch down.

You can test the dryness by sticking your finger directly into the soil. The distance from your fingertip to the first knuckle is approximately 1″ inch. 

Mature plants will need less water and can be watered when the soil is dry 2″ inches deep (or the second knuckle of your finger).

While it often doesn’t need a lot of feeding, you may wish to give your Indian arrowwood a dose of water-soluble fertilizer in early and late spring.

Avoid fertilizers with too much nitrogen unless you want a mass of leaves and fewer flowers.

That said, both a balanced 10-10-10 fertilizer and a 4-8-4 rose fertilizer are great options for more abundant flowers.

This will also promote flower production and healthy growth.

Soil and Transplanting

The mock orange shrub can handle a wide variety of soils, from sandy to clay.

However, since it does best in fertile, well-drained soil, you will want to amend any heavy clay soil with an aggregate such as coarse sand or perlite.

This plant can also handle moist soils but cannot tolerate being waterlogged.

It can also handle a wide range of pH levels, although a mildly acidic soil to neutral pH works best. This plant can also tolerate slightly alkaline soils.

Moreover, the mock orange has some drought tolerance once established. However, don’t let the soil completely dry.

When growing this plant in a container, you must repot it every 2 to 3 years to replace the soil and increase the container size if it’s showing signs of becoming rootbound.

You can improve your poor soil conditions by applying a mulch of organic matter and adding some nutrients.

A layer of compost in the late spring will also help work in the soil.

Grooming and Maintenance

It’s generally best to prune this deciduous shrub as soon as the flowers begin wilting.

This timing allows the plant to heal before cold weather sets in and encourages healthy blooms the following year.

Begin by selecting older stems and prune 1 out of every 3 away at the base, just below a leaf node.

This not only encourages new growth but also increases the airflow through the plant, reducing the risk of disease.

You can also remove any leggy branches to improve the shape.

Finally, remove the top 1/3 of the plant to encourage more new growth the following year.

How To Propagate Wild Mock Orange

Syringa can be propagated in a number of ways, with seeds and stem cuttings being the most popular methods.

For those who want to have more fun, you can also propagate using the suckers or through air layering.

Indian Arrowwood Pests Or Diseases

Gordon’s mock orange is quite hardy once established and can tolerate the salt of sea air, pollution, and tolerance against Japanese beetles.

It is also drought-tolerant and winter-hardy.

Deer tend to leave it alone, although rabbits enjoy nibbling on the plant.

However, aphids are the most common pest, and poor health or exposure can also lead to an infestation of scale, leaf miners, or spider mites.

 When exposed to overly wet, humid conditions, it can be prone to disease problems. 

Additionally, poor watering habits can lead to several fungal infections, including: 

  • Bacterial blight (Pseudomonas syringae)
  • Canker
  • Leaf Spot
  • Gray Mold
  • Powdery Mildew
  • Rust (Gymnosporangium speciosum)
  • Twig Blight (Nectria cinnabarina)

Mock orange is not considered toxic to humans, although the pollen may set off your hay fever.

Additionally, while not toxic to dogs, the plant is poisonous to cats.

Philadelphus Lewisii Uses

The sweet-scented blooms of this low-maintenance shrub attract more than just humans. Bees, butterflies, and hummingbirds also flock to the flowers.

Its arching branches also make a wonderful backdrop for other plants, although you may prefer to put it by a deck, patio, or entryway to take advantage of the scent.

When grouped, they also make excellent screen plants and hedges. Mock oranges shrubs also make specimen plants in the spring, as they provide the first flush of blooms.

When planted as a screen or border, it envelops the space with its sweet fragrance.

While not long-lived, the flowers are also popular for clipping and can be dried for potpourri.

Native Americans have also found extensive uses for this plant. The flowers were used for tea and perfume, while the green leaves and bark were ground and used as soap.

The older wood was used for everything from snowshoes and pipes to tools and even furniture.

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