How to Grow Blue Spur Flowers

Blue spur flower (Plectranthus barbatus)

Dinesh Valke / Wikimedia Commons / CC BY-SA 2.0

In This Article

The Plectranthus genus is large and is related to the Lamiaceae, or mint, family. Its 72 members come in a variety of colors and sizes, but the blue spur flower (Plectranthus barbatus) stands out for its large, upright bushy structure. Also known by the botanical name Coleus barbatus, this plant is native to Africa but has spread abundantly.

These plants can grow up to eight feet in size and have aggressive runners that can choke out native plants if not kept in check. However, this same destructive behavior makes them wonderful plants for creating dense garden beds. The blue spur flower features deep green foliage and sends up stalks with six to eight deep blue-to-purple flowers.

Before planting, be sure to check your area to ensure it is not a pest concern. One way to avoid unwanted spreading is by planting them in containers. The Plectranthus genus does well grown in pots and can even be kept indoors.

Botanical Name Plectranthus barbatus, Coleus barbatus
Common Name Blue Spur Flower, Candlestick Plant, Speckled Spur Flower, Zulu Wonder
Plant Type Perennial 
Mature Size 2 to 8 feet tall
Sun Exposure Sun to partial shade
Soil Type Rich, well-draining
Soil pH Neutral to acidic
Bloom Time Late summer to early fall
Flower Color Lavender
Hardiness Zones 9 to 11
Native Area Africa

Blue Spur Flower Care

Though it has vibrant blooms and a commanding presence, the blue spur flower is an easy-to-care-for addition to your garden. These plants thrive in dappled sunlight and well-draining soil. Try to mimic the environment of the rich forest floor and your Plectranthus barbatus will be very happy.

Because blue spur flowers are such prolific spreaders, occasional pruning is needed to help maintain a bushier, fuller plant. They are quite hardy and can withstand a wide range of temperatures. However, a deep freeze will kill these flowers, so be sure to protect them from very cold temperatures.

Light

Most blue spur flowers can tolerate full sun, but they prefer partial shade to really thrive. They are naturally found in forests or river banks with filtered light, so imitating this type of lighting will create the healthiest specimens.

For indoor lighting, place in an area with bright, indirect lighting for best results.

Soil

These vibrant flowers need rich soil like those found in the forest. Adding some organic matter or compost to your soil before planting will mimic this fertile environment. This will also help the soil to drain well and prevent problems with overwatering.

Water

The Plectranthus genus is drought resistant and, therefore, not very picky when it comes to watering. A regular watering schedule is still beneficial but resist the urge to water it constantly.

If you live in a hot, dry climate, more watering may be needed to keep it healthy. However, be sure not to overwater, as this can quickly kill your plant.

Temperature and Humidity

Consistent with its hardy nature, the blue spur flower can withstand a wide range of temperatures. It does well with heat and can also survive a frost.

A deep freeze will kill this plant though, so be sure to protect it if you have any harsh weather heading your way. One way to do this would be to bring your blue spur flower inside for the winter.

Fertilizer

The Plectranthus family is quite hardy and does not require frequent fertilizing to maintain a full and healthy plant. Adding organic material and compost to the soil before planting will provide its nutrition needs. If you would like to encourage growth and flowering, a general fertilizer will do the job nicely.

Potting and Repotting

The blue spur flower does quite well in pots and can even be brought inside during harsh winters to be kept as a houseplant. If you would like to keep this plant in a pot, make sure you choose one with good drainage.

Since these plants are drought-tolerant, they do not like to sit in water. Too much water can quickly kill them. This makes drainage holes a must.

Propagating Blue Spur Flower

The blue spur flower is an aggressive spreader. It does this by sending out offshoots under the soil. To propagate, you can simply dig up some of these offshoots and move the divided plant to its new area.

Another option for propagation is by using stem cuttings. The cuttings root easily in soil and can be grown without much hassle. Here’s how:

1. Using sharp garden snips or scissors, cut a section from your plant that is a few inches in length.

2. Remove the bottom leaves.

3. Place your cutting in damp soil. Keep moist while rooting.

Your new Plectranthus should take root rather quickly, and, before you know it, you will have another thriving plant.