Plectranthus ‘Magic Mona Purple’: The little-known purple perennial for autumn

A little-known purple perennial really comes into its own at this time.

Anyone who traditionally fills their balcony planters with petunias, geraniums or fuchsias will know the issue: by late summer, their display is over and pots soon look drab. Yet garden centres stock a rather unassuming plant that becomes the secret star of this season – flowering precisely when most others have long since given up.

The little-known plant: Plectranthus ‘Magic Mona Purple’

The focus here is Plectranthus ‘Magic Mona Purple’, which is also frequently sold as ‘Mona Lavender’. Botanically, it belongs to the extensive sage family, originates from South Africa and has been further developed by breeders specifically for containers and hanging baskets.

It grows into an upright, well-branched shrub, reaching around 60 to 70 centimetres in height and roughly the same in spread. A single plant can therefore easily fill a larger pot or hanging basket without becoming overcrowded.

Its bicoloured foliage is especially striking: dark green on the upper side and intensely purple underneath. This makes it decorative and refined even when it is not in flower, rather like a houseplant from a design catalogue.

“The special thing is this: while other balcony plants become tired in autumn, Plectranthus ‘Magic Mona Purple’ only then begins its big show with long purple flower spikes.”

Autumn flowering rather than a summer spectacle

The greatest advantage of this perennial is its flowering time. Although many summer plants put on an enormous display in June and July, they then begin to fade. Plectranthus concentrates on late summer and autumn, sending up numerous long, delicate flower spikes in rich purple at exactly that point.

Each bloom is somewhat reminiscent of sage or lavender – unsurprising, as they are related. The perennial is considered a valuable source of nectar, and bees along with other pollinators readily visit it when the remaining supply is already dwindling.

In very mild, frost-free areas, the plant behaves as a genuinely perennial species. In colder locations, it is not strictly hardy, but it performs very well in a pot and can be overwintered free from frost. With this approach, many home gardeners enjoy its potential for several years.

The ideal position: a shade star for balconies and patios

Plectranthus ‘Magic Mona Purple’ enjoys bright conditions but cannot tolerate relentless midday sun. Partially shaded spots are ideal, where it receives sun in the morning or evening but has some protection during the day.

• East-facing balcony: morning sun followed by bright but non-scorching conditions – almost perfect.
• North-facing balcony: a surprisingly good choice, provided it is bright enough.
• Beneath a canopy: protected from blazing sun and heavy rain.
• Under lightly spaced trees: a filtering leaf canopy provides pleasant light.

This species is particularly beneficial on urban balconies where other plants struggle because of excessive shade. It brings colour to places where often only foliage plants survive.

Choosing the right pot and growing medium

As this perennial is grown in a container, the choice of pot affects both its health and growth. Good drainage holes are particularly important, so that waterlogging does not develop. Plectranthus likes fresh compost, but not wet feet.

Planting step by step

1. Choose a sufficiently large pot or a sturdy hanging basket with drainage holes.
2. Add a drainage layer of expanded clay or coarse gravel.
3. Mix good-quality potting compost with a little compost and a free-draining material, such as broken expanded clay or coarse sand.
4. Position the plant, fill in compost around it and firm it gently.
5. Water thoroughly so the roots make contact with the compost, but do not leave the plant standing in water.

With this foundation, the perennial establishes quickly and soon forms a dense, compact shrub. In hanging baskets especially, it is noticeable how neatly and completely it fills the available space.

Watering, feeding and pruning: care suited to beginners

In day-to-day care, Plectranthus is pleasingly straightforward. Keep the compost evenly and slightly moist, but never permanently wet. Pushing a finger one to two centimetres into the compost soon reveals whether watering is needed.

During the spring and summer growing and flowering period, it can be fed regularly. A liquid fertiliser for flowering plants added to the water every two weeks is usually sufficient. This keeps the plant vigorous, the foliage dense and the blooms abundant.

A light trim maintains its shape and encourages branching. Pinching out shoot tips in spring produces an even more compact, bushier plant. After the main flowering period, individual shoots can be cut back again to keep it tidy.

“A few simple tasks each year are enough to turn an unassuming pot into an impressive, long-flowering autumn display.”

Overwintering without frost: keeping the perennial for years

As Plectranthus ‘Magic Mona Purple’ cannot withstand frost, overwintering is crucial. As soon as the first nights approach zero degrees, the pot should be brought indoors.

A bright place in the house or conservatory is ideal, for example:

• directly beside a window in the stairwell
• a bright hallway
• a not overly warm south-facing window in the living room

The cooler the room, at around 10 to 15 degrees, the less water the plant requires. Moderate watering is enough during this period, and the surface of the root ball may occasionally dry out slightly. Do not feed it during winter dormancy.

In spring, once there is no longer a risk of frost, the perennial can move outside again. Initially, place it in a sheltered, partially shaded spot so that it can acclimatise to wind and sun. After one to two weeks, it is fully ready to return to a hanging basket or large pot on the balcony.

Easy propagation: new plants from cuttings

Anyone taken with this purple autumn perennial can propagate it without difficulty. The plant is very easy to raise from tip cuttings. In spring or late summer, cut younger shoots that have not become woody.

Remove the lower leaves, then place the shoot tip in a glass of water or directly into moist seed compost. Roots often form in water after only a few days. Then pot the cuttings into small containers, position them somewhere bright and water moderately.

In this way, a whole group of identical plants can gradually be produced – ideal for planting several window boxes, hanging baskets or shady corners of the garden in the same colour palette.

Which plants complement the purple perennial?

With its dark leaves and purple flowers, Plectranthus has an elegant, slightly mysterious appearance. Pairing it with other shade-loving plants creates interesting contrasts. Suitable companions include:

• white or cream begonias for pronounced light-and-dark effects
• Hosta varieties with variegated foliage
• ornamental grasses in pots to add lightness
• evergreen ivy varieties as a backdrop

Those who prefer a single focal plant can also fill a larger pot solely with this one species. Its dense habit then makes the container appear like one compact cushion of flowers, supported by matching coloured foliage.

Why it is worth looking beyond the classics

Many home gardeners automatically choose the same summer-flowering plants every year. Plectranthus ‘Magic Mona Purple’ demonstrates just how much potential lies in lesser-known species. Particularly during hot summers, a plant that does not want to stand in glaring midday sunshine, but instead shows its strengths in shaded areas, becomes appealing.

Low maintenance, suitability for pots and hanging baskets, decorative foliage and flowering when others have already faded – this combination makes the perennial a genuine insider tip for anyone wanting to enjoy their balcony planting for longer.

So, anyone who does not want empty planters in September, but would rather celebrate autumn with an abundance of purple colour, will find an unexpectedly dependable companion in this ornamental South African perennial.