The Silver Spurflower (Plectranthus argentatus) is a widely cultivated plant valued for its showy foliage rather than its flowers. This tender perennial is native to Australia but is frequently grown as an annual ornamental in cooler climates. Its signature characteristic is the dense, soft coating of silvery hairs that covers its leaves, providing a unique texture and color contrast in garden settings. This plant is a reliable feature in mixed plantings and containers, introducing brightness and visual interest.
Identifying the Silver Spurflower
The Silver Spurflower belongs to the mint family, Lamiaceae, and is sometimes classified as Coleus argentatus. The species name argentatus is derived from the Latin word for silver, referencing the plant’s most recognizable feature. Its leaves are broadly ovate with scalloped edges, growing up to four inches long. They possess a dense, velvety texture due to a layer of fine, silvery pubescence, which gives the foliage its distinct gray-silver appearance.
The plant typically forms an upright, spreading sub-shrub, reaching two to three feet in both height and width. While the foliage is the main attraction, the Silver Spurflower produces small, pale flowers on tall terminal spikes. These flowers are generally considered insignificant, and gardeners often pinch off developing spikes to encourage the plant to produce more dense foliage.
Essential Growing Conditions
For the Silver Spurflower to thrive and display its best foliage color, providing the correct light exposure is a primary consideration. The plant performs well in a range from full sun to partial shade. In regions with extremely hot summer afternoons, positioning the plant where it receives morning sun and afternoon shade helps prevent leaf scorching and maintains the silvery sheen. Plants grown in overly deep shade may become leggy and lose some of their characteristic compact form.
The soil requirements for this plant emphasize excellent drainage, as the Silver Spurflower is susceptible to root rot in waterlogged conditions. A rich, humusy soil mix amended with organic matter is suitable, allowing for medium moisture retention while ensuring quick drainage. The plant adapts well to a slightly acidic to neutral soil pH, ideally ranging between 6.0 and 7.0.
Since it is a tender perennial, the Silver Spurflower is only winter hardy in USDA zones 10 and 11. In most temperate areas, it must be treated as an annual and replanted each spring once all danger of frost has passed. It thrives in warm temperatures, ideally between 65 and 75 degrees Fahrenheit, and tolerates heat and humidity once established. The plant will suffer significant damage or death when exposed to freezing temperatures, necessitating a late spring planting schedule for outdoor use.
Ongoing Maintenance and Propagation
Consistent moisture is generally beneficial for the Silver Spurflower, but careful watering practices are needed to prevent fungal issues. The best technique involves watering thoroughly, then allowing the top layer of soil to dry slightly before watering again. Avoiding overhead watering is advisable, especially in the evening, because wet foliage that remains damp overnight can increase the risk of leaf spot and other diseases. Mulching around the base of the plant can help regulate soil temperature and conserve moisture.
To sustain vigorous growth and high-quality foliage, a regular feeding regimen is recommended. Apply a balanced, water-soluble fertilizer every four to six weeks during the active growing season from spring through summer. Avoid over-fertilization, which can lead to excessive, soft growth and diminish the density of the silvery hairs. Reduce or eliminate fertilization as temperatures cool in the late summer and fall.
Pruning techniques are important for maintaining the dense, bushy habit of the Silver Spurflower and preventing it from becoming sparse or leggy. Regularly pinching back the growing tips of the stems encourages the plant to branch out laterally, creating a fuller, more compact shape. Pinching off the terminal flower spikes redirects the plant’s energy back into foliage production. For plants that are overwintered, a harder cutback in the late winter or early spring can rejuvenate the plant.
The Silver Spurflower is exceptionally easy to propagate. Stem cuttings are the most reliable and common method, typically taken from healthy, non-flowering tips of the plant. Take a cutting about four to six inches long, removing the lower leaves. Placing the nodes below the soil or water line will encourage root development within a few weeks.
Using Silver Spurflower in the Garden
The unique silvery-gray foliage makes the Silver Spurflower an exceptional contrast plant in landscape design. Its light color and texture highlight and intensify the colors of neighboring plants, particularly those with deep green, burgundy, or brightly colored flowers. Gardeners use it to create a visual break or introduce a cooling, neutral tone to a hot border. The popular cultivar ‘Silver Shield’ is favored for its dense, uniform, and brightly silver foliage.
Due to its mounding and spreading habit, it functions effectively as a border plant, creating a soft, textural edge along walkways or garden beds. It is also superb for container gardening, often used as a “spiller” plant that cascades over the edges of pots and hanging baskets. This habit softens the container’s lines and allows the silvery texture to contrast with the arrangement’s other elements. It is also a successful houseplant, thriving indoors in a bright, cool location, which provides an option for overwintering outdoor specimens.