Spur Flower (Plectranthus) – The Complete Guide

The spur flower (Plectranthus) is not related to the real frankincense tree (Boswellia) but exudes a very similar, wonderfully ethereal-spicy fragrance. It is a real sensory delight on sunny seats on the balcony, terrace, or even in the living room!


The spur flower belongs to the large genus of herbaceous perennial plants with the botanical name Plectranthus, within the Lamiaceae family. This genus includes a handsome number of over 350 species, some of which differ from each other in growth and habit.

Spur flowers come mainly from tropical to subtropical areas of Africa and the Far East. But some species are also native to parts of Australia and New Zealand as well as the Near East.

Thus, depending on the species, they colonize quite diverse habitats ranging from warm, moist forests to cooler, maritime climates such as the Cape region of South Africa. The vast majority of Plectranthus species are not hardy.

Basically, only the cultivated varieties of the two common species Plectranthus glabratus and Pectranthus forsteri are called spur flowers. Pectranthus coleoides is also included, but is less common in its pure form.

The species Pectranthus glabratus is native to the tropical Far Southeast, parts of India, Thailand, Sri Lanka, and Vietnam. Whereas the species Plectranthus forsteri is native to the southwestern Pacific Islands, in particular Fiji and Vanuatu.

The spur flower emits a spicy ethereal fragrance. It is reminiscent of that of the true frankincense tree (Boswellia carterii), but the spur flower is not remotely related to it.

Nevertheless, spur flowers, with their scent character, have a very high value for the sensory design of balconies and terraces. In addition, they supposedly repel moths and mosquitoes.

However, not only spur flowers but also most other Plectranthus species have quite intense and ethereal scents. Some of them also serve as spice plants.

Origin at a glance:

  • Plectranthus species are generally native to much of tropical to subtropical areas in Africa, the Far East, and Australia.
  • Usually the name spur flower refers to varieties of the species Plectranthus glabratus and Plectranthus forsteri. These are native to tropical Southeast Asia and the southwestern Pacific Islands
  • There is no botanical relationship with true frankincense tree (Boswellia), only a similar spicy-etheric scent.


Plectranthus species usually grow as perennials, although some are annuals only or form a semi-shrub habit. There exist also succulent varieties of Plectranthus plants.

The erect to overhanging stems form long shoots and are hairy.

Especially the spur flowers form a more hanging than upright habit. They grow to a total height of only 8 to 12 inches (20 to 30 cm) but develop very long hanging shoots that take up a lot of space.

This is something you should take into account, especially when growing it on a balcony. Spur flowers also grow very quickly.

Growth characteristics in keywords:

  • Plectranthus species are mostly perennials, rarely annuals, sometimes semi-shrubs.
  • They have hairy, erect to pendulous stems.
  • Plectranthus plants show distinctly drooping habit with 8 – 12 inches (20 – 30 cm) height and long shoots
  • Rapid growth


The leaves are the main thing in spur flowers from an ornamental horticultural point of view. With their shape and coloration, they have much more to offer aesthetically compared to the inconspicuous flowers.

Spur flowers therefore clearly belong to the foliage ornamental plants in garden culture.

As with most Plectranthus species, the foliage leaves of spur flowers attach to the richly branched stems in opposite directions. They are short-stalked and have an ovate outline with softly notched leaf margins.

The pretty variegation is characteristic of the varieties sold in specialized shops. It usually appears in a fresh green center and shows irregular edges in a creamy white color.

The essential oils contained in the leaves are, of course, responsible for the incense-like fragrance that is intensely emitted, especially when touched.

Leaf characteristics in brief:

  • Leaves are spur plants main ornament
  • they have short stalked, ovate, notched leaf edges
  • Cultivated varieties have pretty variegation
  • Essential oils exude spicy fragrance


As already mentioned, the flowers of spur flowers only play a minor role.

They are small, inconspicuous, rispy inflorescences of a whitish hue that appear between about May and August.

Which Location is Suitable for a Spur Flower?

Spur flowers need a sunny, warm location, but can also cope with semi-shady places.

However, you should ensure a few hours of sunlight in any case, if you value a vital, compact growth and a beautiful formation of the leaf variegation.

In partial shade, the plant can become somewhat sparse and lacking in foliage. Because of its rich overhanging growth with the long shoots, cultivation in the plant hanging basket is very advisable.

This way, the plant not only has enough space downwards but also shows off its hanging habit to the best advantage.

The spur flower can also be kept indoors all year round. There you should give it a bright window place. It does well with a comfortable living temperature of 64 to 68 °F (18 to 20°C).

To remember:

  • A sunny, warm location is best, but partial shade is also possible.
  • Growth and variegation perform best with plenty of light.
  • The spur flower is ideal in hanging baskets.

The Spur Flower On the Balcony

A spur flower looks very nice on a balcony. There it can enhance a rather cramped seating area not only with its leaves, which are very pretty in detail but also with its fragrance, which comes out intensely when touched.

In addition, a balcony often provides good conditions for a spur flower due to its closeness to the house and its sheltered character. Of course, it is best if it faces south.

What Soil Does the Spur Flower Need?

When it comes to the substrate, spur flowers are not very picky. It should only be reasonably rich in nutrients and permeable.

You can best use a universal potting soil and enhance it with some leaf compost. This will provide your spur flower with a permanent supply of good, organic fertilizer.

Loosen the soil even more with some sand to ensure good water drainage. Some mineral content will also help retain water.

Watering the Spur Flower

Spur flowers are relatively thirsty and require your continued attention. Especially in the summer and when they are standing or hanging in sunny conditions.

If very warm, sunny weather prevails, you will need to water the plant at least once each day. Make sure the soil stays moist at all times, but avoid waterlogging.

In addition, it is also good for the tropical plant to get a refreshing shower from the water disperser from time to time. This is especially recommended if you keep it indoors all year round. It is best to use soft, lukewarm water.

The spur flower is also suitable for hydroponics.

To remember:

  • Water relatively much, especially on hot summer days.
  • Avoid waterlogging.
  • In addition, occasional showering.
  • Use soft, lukewarm water.

Fertilizing the Spur Flower Properly

During the main vegetation phase, approximately from May to August, you can provide the spur flower with some liquid fertilizer for balcony or green plants about every 14 days. In winter, do not fertilize it.

You should fertilize a freshly purchased or repotted specimen after about 6 weeks at the earliest.

Are Spur Flowers Winter Hardy

Like most Plectranthus species, incense plants native to the warm tropical regions of Far Asia are naturally not equipped for colder winters. Permanent cultivation outdoors is therefore not possible in areas where it gets cold in winter.

Wintering the Spur Flower

If you keep a spur flower outdoors in summer, you must bring it indoors in autumn, as soon as the first frosts appear, because of its sensitivity to cold.

Although it is not accustomed to seasons like ours from its homeland, you should adjust the environmental conditions a little in winter. After all, light deprivation is unavoidable.

The resulting pause in vegetation must also be accompanied by a slightly lower ambient temperature and less watering. In the winter quarters, the temperature should be about 54 to 61 °F (12 to 16 °C).

And you should reduce watering to a minimum. Water the spur flower only enough so that the root ball does not dry out completely.

From March, when the sunlight increases noticeably, you can start watering again. And you can also start fertilizing the plant again.

Pruning the Spur Flower Properly

Actually, spur flowers do not require pruning. If you keep them in a sunny and warm place, they form a beautiful, compact growth.

And if you keep them in a hanging basket, the long hanging shoots give them their typical character.

Nevertheless, they can of course become too long for some people. In this case, you can shorten them without any problems. You should also prune out any shoots that have become overgrown or dried out.

Use sharp cutting tools for pruning if possible so as not to bruise the somewhat delicate stems and do not cut into the woody lower areas.

Propagating the Spur Flower

The best way to propagate spur flowers is via cuttings. To do this, cut about 3 inches (7 cm) long cuttings from healthy shoots in spring, preferably just below a leaf base.

Remove the leaves in the lower part and put the prepared cutting into a planting container with growing soil. Place it in a bright, warm place with an ambient temperature of around 68 °F (20°C).

Keep the soil evenly moist, if possible. The cuttings have a good chance of growing in an evenly moist warm microclimate under foil or in a mini-greenhouse.

As soon as the cuttings form new shoots, you can place them in a larger planter with more nutrient-rich soil.

Is the Spur Flower Poisonous ?

The frankincense plant is not poisonous. Although Plectranthus glabratus and Plectranthus forsteri varieties are not suitable as spice plants, they are not dangerous to curious small children or pets.


You can find many crossed cultivars especially of Plectranthus glabratus and Plectranthus forsteri in specialized shops. These differ mainly a little in the coloring of the leaves.

The best known and most sold variety is probably Plectranthus forsteri ‘Marginatus‘. It is attractively variegated with the typical creamy-white banding around a fresh green leaf heart.

The cultivar Plectranthus forsteri ‘Aureus Variegatus‘ has somewhat yellowish-green leaves. It is mainly characterized by long, beautifully drooping shoots.

Another relatively popular variety is Plectranthus forsteri ‘Nico’. Its leaves have no variegation but look no less attractive with their fine-margined, pointed outline and the combination of the dark green upper side and the purple lower side.