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What is Philadelphus?

Debra Durkee
Debra Durkee

Philadelphus is a genus of small, deciduous shrubs found throughout North America. Generally showing a rapid growth rate and attractive flowers, the genus belongs to the family Hydrangeaceae and consequently has much in common with the popular hydrangea shrubs. Most popular among the genus is the sweet mock-orange, the scentless mock-orange, and the hoary mock-orange.

The Philadelphus coronarius, or sweet mock-orange, is a large, hardy shrub that can survive winter temperatures down to -30°F (about -31°C). Like other members of the Philadelphus genus, the sweet mock-orange sheds its leaves in the winter and regrows them in the summer without displaying the colorful fall foliage of many deciduous plants. The sweet mock-orange follows the spring leaves with fragrant white flowers that cover the entire form of the rounded shrub. Within the species, there are a number of cultivars that present gardeners with variations on the basic plant; these include the yellow-leaf aureus and the dwarf nanus.

Man mowing the grass
Man mowing the grass

As its name suggests, the hoary mock-orange is a spindly member of the Philadelphus genus. It has the same white flowers as its fuller cousins, but the hoary mock-orange has thinner branches and leaves and grows taller. Fruits remain on the bush throughout the summer and fall, appearing after the flowers disappear.

The scentless mock-orange also has a name suggestive of its traits. This shrub sports showy white flowers, as other members of the Philadelphus genus do, but lacks their distinctive fragrance. Leaves are lighter on the bottom than they are on top, and hide reddish-brown bark. A relatively small shrub, the scentless mock-orange generally reaches a mature height of around 10 feet (about 3 m).

Traits shared throughout the genus include oval leaves that are green in the summer and simply fall in the autumn without turning brilliant colors first. Leaves are opposite, meaning they occur in pairs down thin branches arcing out from the thicker, main branches of the shrub. In most varieties of Philadelphus, they are simple leaves with non-serrated edges, although some cultivars can sport more complex leaves. Flowering generally occurs in the late spring and early summer, with small fruit capsules sectioned into four compartments that last through the autumn.

Hybrids of the species share many of the same traits, but have generally been created for one or two differences. Some, like the Virginal, have double flowers as opposed to the normal, single row of petals. As the scent of the Philadelphus shrubs is so attractive to so many, some hybrids have been created to be even more fragrant than the standard species.

Frequently Asked Questions

What is Philadelphus and where does it originate from?

Philadelphus, commonly known as mock orange, is a genus of about 60 species of shrubs native to North America, Asia, and Europe. It's celebrated for its fragrant white flowers that resemble orange blossoms, hence the name. The genus was named by Linnaeus, a Swedish botanist, in the 18th century, and it belongs to the Hydrangeaceae family.

How do you care for Philadelphus plants?

Caring for Philadelphus involves planting them in well-drained soil with access to full sun or partial shade. They require moderate watering, especially during dry spells, and benefit from annual pruning to remove old wood and encourage new growth. Fertilization is not typically necessary, but a layer of mulch can help retain soil moisture and suppress weeds.

When is the best time to prune Philadelphus, and why is it important?

The best time to prune Philadelphus is immediately after it finishes blooming, usually in late spring or early summer. Pruning is crucial as it helps maintain the shape of the shrub, encourages the growth of new flowers, and prevents the plant from becoming too woody and overgrown, which can diminish its flowering potential.

Are Philadelphus plants resistant to pests and diseases?

Philadelphus shrubs are generally hardy and resistant to many pests and diseases. However, they can occasionally be affected by common issues such as powdery mildew or aphids. Good air circulation, proper spacing, and keeping the area free of debris can minimize these problems and keep the plants healthy.

Can Philadelphus be used in landscaping, and if so, how?

Philadelphus is an excellent choice for landscaping due to its lush foliage and aromatic blossoms. It can be used as a specimen plant, in mixed borders, or as part of a hedge. Its ability to attract pollinators like bees and butterflies also makes it a valuable addition to wildlife gardens.

What are some popular varieties of Philadelphus to grow?

Popular varieties of Philadelphus include 'Belle Etoile' with its single flowers and maroon centers, 'Virginal' known for its double blooms, and 'Aureus', which boasts golden-yellow foliage. Each variety offers a unique aesthetic, with flowering times ranging from late spring to early summer, depending on the species and local climate conditions.

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