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Spritzhenry's Garden

Prostanthera denticulata 'Mint Royale'

Genus: Prostanthera.

Species: Prostanthera denticulata.

Photos of this plant

  • Prostanthera_mint_royale_

Reminders for this plant

Due over 13 years ago:

Care of plant

Zone 9 is shown as just in your area down to -1. There are lots of different species but they are all similar in requirements. A local hps member has one that seems to have come through the winter but it was heavily fleeced. They are quite short lived she said.

Under glass, grow in pots of soil-based potting compost. Provide good light and airy conditions. In the garden, if you have a suitable climate, prostantheras can be grown in a variety of soil types, but thrive in a lightly textured, well-drained soil. Newly planted specimens need care and attention until they are well established. Autumn is a good time to plant, leaving the winter months for becoming established, and spring for rapid growth.

Prostantheras generally prefer morning sun with afternoon shade, although many species tolerate light shade all day. The root systems of these plants are shallow, so planting in a sheltered position amid rocks, larger shrubs and trees is worthwhile, to prevent their being blown over in strong winds or rain. Most species will flower in the first year.

Most also benefit from regular pruning, especially straight after flowering. From the time of planting, tip pruning should be undertaken to encourage the development of a compact, bushy shape. Regular tip pruning is more effective than occasional heavy cutting, as cutting into older wood can often set back the plant severely or even kill it.

The root system of this plant is close to the surface, so avoid disturbing soil near the plant. A mulch of coarse river sand or decayed leaf mould will help reduce weeds and maintain moisture, as will the placement of large rocks around the roots.

Prostantheras can be propagated from seed or cuttings. Growing from cuttings is the easiest method for these plants, as they flower earlier and are true to type. Cuttings of side shoots taken in late spring after flowering, or in early autumn, are best. Place cuttings in a propagating case, with bottom heat and keep the compost moist at all times. Since cuttings are easy to strike, it is a good idea to have new plants always under way, especially if cultivating some of the more spectacular flowering forms.

Prostantheras will take light frosts and are fairly free from the usual insect pests and diseases, possibly due to the aromatic oils contained in the foliage. Phytophthora root rot is possibly the cause of most plant failures. This fungus thrives in warm weather, in water-logged soils.