Plumbago, known botanically as Plumbago auriculata and commonly as Cape Plumbago or Blue Plumbago, is a popular garden plant. Recognized for its vibrant blue, phlox-like blossoms, it offers a continuous display that enhances various landscape designs. Its appealing blue hue, uncommon in the plant world, makes it a favored ornamental.
Plumbago’s Growth Characteristics
Understanding the growth habits of Plumbago auriculata is important for gardeners. The term “invasive” typically describes a non-native species that causes environmental or economic harm by aggressively outcompeting native plants and disrupting ecosystems. While Cape Plumbago is not classified as truly invasive in many regions, it exhibits vigorous, sprawling growth that gardeners may perceive as aggressive.
This plant spreads through several mechanisms, including vigorous root suckering and rapid stem growth. Its arching stems can root where they touch the ground, allowing the plant to expand its footprint significantly. While self-seeding can occur, it is often less common compared to its vegetative spread.
The plant’s adaptability to various soil types and climates further contributes to its robust growth. It thrives in conditions from full sun to partial shade and in well-draining soils, allowing it to establish quickly and spread effectively. This aggressive growth habit can result in dense thickets, potentially crowding out other desired plants in a garden setting.
Managing Plumbago’s Spread
Controlling the spread of Plumbago auriculata involves consistent gardening practices. Regular pruning is a primary method for managing its size and sprawling habit. This includes routine maintenance to shape the plant and encourage new blooms, as flowers form on new growth. Hard cutbacks in late winter or early spring can significantly reduce the plant’s overall size; removing about one-third promotes denser foliage and more profuse flowering.
Containment strategies are also effective. Planting plumbago in large pots or containers restricts its root spread, preventing it from taking over garden beds. For plants in the ground, installing root barriers creates a physical boundary to prevent rhizomes and suckers from spreading. When selecting a planting site, choose locations where its spread can be tolerated or easily managed, such as open areas or slopes.
Regular removal of suckers and unwanted seedlings is another important task. Plumbago produces suckers from its rhizomes, which should be dug up and removed to control spread. Consistent removal is necessary to prevent unintended colonization. While plumbago is a robust plant, wearing gloves during handling is advisable as it can cause contact dermatitis in some individuals.
Alternatives to Plumbago
For gardeners seeking plants with similar aesthetic qualities but less aggressive growth, several alternatives exist. Blue Salvia, such as ‘Blue Mound’ or ‘Indigo Spires’, offers vibrant blue flowers and tolerates dry conditions once established. These salvias provide a long blooming season and attract pollinators.
Another option is Dwarf Plumbago (Ceratostigma plumbaginoides), a lower-growing groundcover with deep blue flowers from late summer into fall. This plant spreads more moderately by rhizomes and offers attractive reddish-orange fall foliage. For warmer climates, Agapanthus, or Lily of the Nile, provides stately blue blooms with a different texture and less aggressive spread. These alternatives offer similar visual appeal without the extensive management required for Plumbago auriculata’s vigorous growth.