The question of whether a Mock Orange is invasive or merely aggressive is complex because the common name refers to two entirely different plants. Gardeners often confuse the terms, often using “invasive” to describe any plant that spreads vigorously. However, the true definition of an invasive species involves a non-native organism that causes environmental or economic harm. An aggressive plant is typically native or naturalized and simply grows vigorously in a cultivated area. Understanding which plant you have is the first step in determining its growth habit and management needs.
Defining the Plants Called Mock Orange
The name Mock Orange is most commonly applied to the genus Philadelphus, a group of deciduous shrubs prized for their fragrant white flowers that resemble orange blossoms. These traditional garden Mock Oranges include species native to Europe, Asia, and North America, such as Philadelphus coronarius and Philadelphus lewisii. A completely different plant that shares the common name is Murraya paniculata, also known as Orange Jessamine. This evergreen, tropical shrub belongs to the citrus family, which explains its similar flower fragrance. While Murraya paniculata can be legally classified as invasive in warm regions like Florida and Hawaii, the temperate Philadelphus species are the primary subject of the “aggressive versus invasive” confusion for most home gardeners.
The Non-Invasive Status of Philadelphus Species
The Philadelphus species generally grown in gardens are not considered invasive in temperate climates, as they do not cause widespread ecological or economic damage outside of a cultivated setting. For example, the popular Sweet Mock Orange (Philadelphus coronarius) is classified as naturalized rather than invasive in North America. The aggressive behavior associated with Philadelphus is due to its natural growth pattern of suckering. The shrub sends out new shoots, called suckers, from the base or root system, allowing it to slowly expand its footprint and form a dense colony. The small, seed-filled capsules produced by Philadelphus are not typically dispersed widely enough to colonize natural areas, unlike the bird-attracting berries of Murraya paniculata.
Managing Aggressive Spreading
Since the garden Mock Orange (Philadelphus) is aggressive rather than invasive, control focuses on managing its suckering habit and overall size. The most effective way to prevent the plant from colonizing a larger area is through consistent removal of suckers as soon as they appear, cutting or pulling them directly from the root system. Physical barriers can also limit the spread; installing a root barrier, such as thick plastic or metal edging sunk vertically into the soil, can contain the lateral spread of new shoots. For older, well-established shrubs, rejuvenation pruning is beneficial, involving cutting back three or four of the oldest, thickest stems right down to the base each year immediately after flowering. For smaller garden spaces, selecting a dwarf cultivar, such as Philadelphus ‘Manteau d’Hermine’, and growing it in a large container can eliminate the need for extensive spreading control.