The purple Coleus (Plectranthus scutellarioides) is prized for its dramatic, deep foliage, providing a striking color accent to gardens and indoor spaces. Unlike many plants grown for their flowers, the appeal of the Coleus lies entirely in its velvety leaves, which display rich shades of maroon, burgundy, and nearly black purple. A member of the mint family, the Coleus is known for its relatively easy cultivation. This guide provides the steps required to successfully grow and maintain a purple Coleus, ensuring maximum color saturation and plant vigor.
Initial Setup: Environment and Planting
Achieving the deepest purple coloration depends heavily on providing the correct light exposure. For dark-leaf varieties, the ideal environment is bright, indirect light or partial shade, which encourages the production of the anthocyanin pigments responsible for the color. Too much direct, intense afternoon sun can cause the purple leaves to fade or “bleach” to a duller tone. Conversely, too much shade will cause the color to revert to green. An east-facing location, receiving gentle morning sun and shaded during the afternoon, often provides the perfect balance for vibrant color saturation.
The Coleus is sensitive to cold and should only be planted outdoors once all danger of frost has passed, and nighttime temperatures are consistently above 60°F (15.5°C). The plant thrives in warm conditions, but its roots require a rich, loose, and porous soil structure. A planting medium consisting of organic matter like compost, blended with aerating materials such as perlite or vermiculite, provides the necessary drainage. The soil should maintain a slightly acidic to neutral pH, ideally between 6.0 and 7.0, to support nutrient uptake and growth.
Ensuring proper drainage is paramount to prevent “wet feet,” a condition that leads to root rot. When planting directly into the ground, loosen the soil to a depth of six to twelve inches and incorporate organic amendments to enhance fertility and texture. For container planting, always use a quality potting mix in a pot with sufficient drainage holes, allowing excess water to escape. Space multiple plants 12 to 18 inches apart to allow for mature growth and adequate air circulation, which helps deter fungal diseases.
Routine Maintenance: Watering and Feeding
Consistent moisture is a requirement for the Coleus, which prefers soil that is always moist but never saturated or soggy. This balance is achieved by watering when the top inch of soil feels dry to the touch, known as the finger test. Allowing the plant to completely dry out quickly leads to wilting and stressed foliage. Overwatering can drown the roots, causing rot and resulting in yellowed leaves.
Container-grown plants require more frequent watering than those in garden beds, sometimes needing attention daily during hot, dry weather due to the limited soil volume. When watering, aim the stream at the soil and the base of the plant, avoiding wetting the foliage, which can encourage leaf spot diseases. A layer of organic mulch around the base of the plant helps retain soil moisture and stabilize root temperature, reducing the need for constant watering.
Coleus benefits from regular feeding, particularly when grown in containers where nutrients leach out quickly. During the active growing season (spring through summer), apply a balanced liquid fertilizer every two to four weeks. The formula should contain equal ratios of nitrogen, phosphorus, and potassium, promoting foliage growth over flowering. Adhere to the recommended dilution rates, as over-fertilizing causes rapid, leggy growth that dilutes the purple color.
Regular inspection of the foliage is a necessary preventative measure against common pests. Aphids, spider mites, and whiteflies can infest the plant, particularly on the undersides of the leaves. Checking the leaves every few days allows you to catch potential infestations early, before they cause significant damage. Immediately removing affected leaves or gently wiping them with a damp cloth is often enough to control minor pest issues.
Shaping and Saving Your Coleus
Pruning is an intentional action that directly influences the plant’s shape and density. To encourage a compact, bushy form, regularly pinch back the growing tips. This process involves removing the top two leaves and the stem tip, cutting just above a leaf node (a set of existing leaves). Removing the apical meristem, the primary growth point, forces the plant’s energy into the side shoots, resulting in a fuller habit.
The removal of flower spikes, known as deadheading, should occur as soon as they emerge. Coleus flowers are typically insignificant small spikes of blue or white, and their development consumes substantial energy. Removing these spikes redirects the plant’s resources back into producing large, colorful foliage, which is the plant’s main ornamental feature.
The material removed during pruning can be used to create new plants through propagation. Coleus cuttings root readily, making it simple to duplicate favorite specimens. Take a stem cutting four to six inches long, cutting just below a leaf node, and remove all leaves except for the top set. Cuttings can be placed directly into a glass of water or a container filled with moist, sterile potting mix.
Within one to two weeks, water cuttings will develop visible roots, indicating they are ready to be potted into soil. In regions outside of USDA hardiness zones 10 and 11, where Coleus is treated as an annual, the plant can be saved by overwintering it indoors. Before the first frost, or when outdoor temperatures consistently drop below 50°F (10°C), either dig up a mature plant or bring containers inside. Check the plant thoroughly for pests before moving it indoors to prevent introducing insects into the home environment.
When overwintering, place the Coleus in a location that receives bright, indirect light, such as a south or west-facing window. Indoor care requires a significant reduction in watering frequency, as the plant’s growth slows during the colder months. The goal is to keep the soil only slightly moist. The combination of reduced light and excessive water is a primary cause of root rot in overwintered plants.