Prostanthera

( pro - stan - THEIR - uh )

At-A-Glance Information

This genus of evergreen shrubs and subshrubs, commonly called Mint Bush, Mintbush or Native Mint, includes species which need full sun and moderate water to perform well in the landscape. All species in the genus are native to Australia and are prized for their fragrant foliage and profuse flowers that bloom in shades of blue, purple and white, often with patterned throats. They are short-lived plants but grow quickly and vigorously. Use Native Mint as an informal hedge or screening plant, as members of sensory, herb, or edible gardens, mass-planted on hillsides, or simply in containers on patios and walkways.

Prostanthera Species and Varietals

The genus Prostanthera includes around 100 species and is a member of the Mint family (Lamiaceae). The plants in this genus are closely related to those in Westringia (Coast Rosemary). Mint Bush grows well in USDA hardiness zones 7-10 or Sunset growing zones 14-17 and 19-24, though this varies somewhat depending on the species cultivated. For more information, see the species descriptions below. To find your zone, click here: Zone Map.

Prostanthera cuneata (Alpine Mint Bush, Rough Mint Bush, Australian Mint Bush)
This species grows to 3 feet tall and 3-5 feet wide, with a dense habit. Leaves are dark green and flowers are white with purple-spotted throats, blooming mainly in spring and sporadically into fall. Alpine Mint Bush grows well in USDA hardiness zones 7-10, thriving in mild winter regions. Cultivars include 'Badja Pink' (upright to 5-6 feet tall with larger leaves than the species and pale lilac blooms) and 'Cool Mint' (compact to just over 2 feet tall, with dark green glossy leaves and white flowers with purple throats).

Prostanthera spp. Hybrids (Hybrid Prostanthera, Hybrid Native Mint, Hybrid Mint Bush)
These plants were bred for their resiliencies, shape, size, or flower color. Cultivars are described below:

'Poorinda Ballerina'
To 6.5 feet tall with white flowers that have orange and purple markings. Non-aromatic.

'Poorinda Bride'
To 4-6 feet tall and wide. Leaves are olive-green and flowers are white to violet with orange-yellow throats.

'Ragged Robin'
Upright to 10 feet tall by 6.5 feet wide, with strongly aromatic leaves and mauve-blue flowers.

Prostanthera nivea (Snowy Mint Bush, Snowy Mintbush)
This species has an upright, compact habit reaching 3 to 13 feet tall and 3 to 10 feet wide with silvery, narrow leaves. Flowers are blue and bloom in springtime. Snowy Mint Bush is native to eastern Australia, and is suited for growing in USDA hardiness zones 9a-11. Varietal Prostanthera nivea induta is a smaller-growing shrub to 3 to 7 feet tall with white woolly hairs on branches and leaves.

Prostanthera ovalifolia (Mint Bush, Purple Mintbush, Oval-Leaf Mintbush)
Erect grower to 8-10 feet tall and 5-8 feet wide. Springtime flowers are purple-pink and leaves are medium green. Purple Mintbush needs more water than other species and is suited for growing in USDA hardiness zones 9-11 or Sunset climate zones 14-17 and 19-24.

Prostanthera rotundifolia (Round-Leaf Mintbush, Round-Leaved Mint Bush, Native Mint Bush, Native Mintbush)
This species reaches 6 feet tall and 5 feet wide with small round leaves and blue-purple flowers. It is native to southeastern Australia (New South Wales, Victoria, Tasmania, and South Australia). Cultivars include 'Ghost Cave' (with grey-green foliage purple flowers), 'Glen Davis' (with profuse dark purple flowers), and 'Rosea' (to 3-4 feet tall with dark green leaves and deep rose-pink flowers).

Caring for Prostanthera

Mint Bush does best in full sun (ideally at least 6-8 hours of direct sun per day). They need well-draining soil with an acidic to neutral pH (between 6.1 and 7.8). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, keep soil consistently moist but not waterlogged, and use deep waterings rather than regular frequent waterings.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. Prune carefully; avoid cutting into bare wood or doing any other hard prunings. Cutting back past green, leafy foliage often kills the branch or sometimes the entire plant. These shrubs can survive for between 5 and 15 years in the landscape before needing to be replaced. Towards the end of their ornamental life, they tend to become woody and develop bald patches.

Caring for Prostanthera in Containers
Prostanthera shrubs are wonderful in the ground, but can also be grown in containers. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a fast-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Prostanthera plants grown in containers will need more frequent irrigation than those grown in the ground, but are still considered very drought-tolerant. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

How to Harvest Prostanthera
Prostanthera, or Mintbush, produces aromatic, edible foliage that adds depth to savory and sweet dishes. The species most commonly cultivated for their edible foliage are Prostanthera incisa (Cut-Leaf Mint Bush), Prostanthera rotundifolia (Round-Leaf Mint Bush), and Prostanthera sieberi (Edible Native Mint). Foliage has a strong minty, Eucalyptus, or Oregano-type scent and flavor. They are harvested during their active growing season from spring through fall. The best time of day to harvest is in the morning, after dew has dried but before the heat of the day sets in; this is when the aromatic oil content is at its peak. Using clean snips, sever individual leaves or soft tip growth. Never remove more than a quarter to a third of the plant's foliage at any one time to avoid shocking it. Fresh leaves can be used as culinary seasoning or garnish or in herbal tea. They are also perfect for herb butters and spreads. Foliage can also be air-dried, either on stems or removed from them. Place stems in a bundle and hang them in a dark, dry, cool area with good ventilation. Leaves can be dried on a screen. They should be completely dried in 1 or 2 weeks. To dry them in the oven, remove leaves from stems and place them on a baking sheet in a single layer. Place them in the oven set at under 180 degrees Fahrenheit and bake them for 2 to 4 hours, monitoring closely so leaves do not begin to singe and lose flavor. Dried leaves can be used as a culinary seasoning, in potpourri mixes, or as an addition to herbal teas.

Disclaimer: Information contained on this website is strictly and categorically intended as a reference to be used in conjunction with experts in your area. Foraging and consumption of plant parts should never begin without the guidance and approval of a local plant specialist. The providers of this website accept no liability for the use or misuse of information contained in this website.

Propagation

Prostanthera can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your shrub, follow the instructions below:

Propagating Prostanthera by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Prostanthera by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination can take between 1 and 6 months from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.