Plectranthus ‘Magic Mona Purple’: The easy purple perennial for shaded balconies

Many keen gardeners will recognise the pattern: hanging baskets and pots are bursting with colour in spring, but by late summer they contain little more than tired petunias and dried-up remnants. Yet there is one plant that truly gets going when most traditional balcony favourites are already fading – and it needs very little effort to look after.

Why this purple perennial is becoming a well-kept secret

The plant is called Plectranthus ‘Magic Mona Purple’, although it is often sold as ‘Mona Lavender’. Native to South Africa, it was selected there by breeders specifically for containers and hanging baskets. It is often tucked away among the standard summer-flowering plants in garden centres. Those who try it once generally continue growing it.

Rather than trailing or cascading, it develops into a densely branched bush. It reaches roughly 60 to 70 centimetres in height and spreads to a similar width. This means it rapidly fills pots, large window boxes and hanging baskets without leaving bare gaps.

The standout feature is that this perennial puts on its main display when many other plants are already slipping into autumn mode.

As geraniums and similar plants gradually lose vigour, Plectranthus begins a lengthy flowering season in late summer and autumn. Its shoots become covered in violet flower spikes resembling delicate lavender candles. At the same time, the undersides of its leaves shine a rich purple while the upper surfaces remain dark green, creating a striking two-tone effect even when it is not in flower.

The right position for Plectranthus ‘Magic Mona Purple’

Plectranthus ‘Magic Mona Purple’ prefers bright sites away from intense sunshine. Suitable locations include:

• east- or north-facing balconies
• patios with a light roof overhang
• partially shaded corners of a courtyard
• places beneath lightly canopied trees

Direct midday sun, especially at the height of summer, puts the plant under strain. Its foliage may scorch and the compost dries out too quickly. In partly shaded spots where many familiar balcony plants barely flower, however, Plectranthus really comes into its own.

There is a firm limit when it comes to temperature: it cannot tolerate frost. It may survive outdoors through winter in exceptionally mild areas, but conditions become risky once temperatures approach 0°C. In the UK, the usual routine is generally as follows:

• From May: move it onto the balcony or patio
• Late summer to autumn: its main flowering period outdoors
• Before the first frost: bring it into the house, conservatory or a bright stairwell

Planting in a pot or hanging basket: getting started successfully

To allow this perennial to reach its full potential, it needs a suitable container. Good options include:

• large window boxes with sufficient depth
• sturdy hanging baskets with strong supports
• stable planters with several drainage holes

A nutrient-rich but free-draining potting mix is ideal. A practical blend can include:

• multipurpose compost or compost for container plants
• a little well-rotted compost
• a loose drainage material, such as expanded clay or coarse sand

After planting, gently firm the compost and water thoroughly, ensuring that no water is left standing in the saucer. During its first few weeks, the plant establishes itself quickly, producing fresh shoots and naturally becoming denser.

Everyday care: little work, impressive results

Plectranthus is undemanding when watering, provided you strike the right balance. The compost should remain evenly slightly moist, but it must not become waterlogged. Do not allow the root ball to dry out completely, as the plant will quickly start to droop.

For a long and generous flowering display, regular but restrained feeding is beneficial:

• add liquid flowering-plant feed to the watering can every two weeks
• or apply a slow-release fertiliser in spring, for example in pellet or fertiliser-stick form

Very little else is required. If you have the time and inclination, lightly trim the shoot tips in spring and again after the main flowering flush. This encourages the bush to branch more freely and stay compact without developing sparse patches.

With just a few jobs each year, an unremarkable pot can become a dense, autumn-flowering mound – perfect for shaded balconies that might otherwise soon look dull.

Helping the perennial survive for several years

In our climate, Plectranthus ‘Magic Mona Purple’ is not considered hardy. Anyone wishing to keep it for several years should bring it indoors in good time. A bright spot behind glass is enough; an ordinary room is perfectly suitable, provided there is not a radiator blasting heat directly beneath it.

Water sparingly over winter. Allow the upper layer of compost to dry slightly before watering again. Growth and flowering reduce noticeably during this period, as the plant effectively takes a rest. In spring, once the days become longer, it starts producing new growth and can return outdoors once nights are frost-free.

Propagating from cuttings: new plants for next to nothing

If you become fond of this perennial, there is no need to buy fresh plants every year. Plectranthus is easy to propagate from cuttings:

• In late spring or summer, cut a non-woody shoot measuring around 8–10 centimetres.
• Remove the lower leaves, leaving only two or three pairs at the top.
• Place the cutting in a glass of water or straight into a small pot filled with seed compost.
• Keep it somewhere bright but out of strong sunlight, and maintain slight moisture.

Roots will form within a few weeks. The young Plectranthus can then be moved into a larger pot and later used to fill window boxes or hanging baskets too.

Which balconies benefit most from Plectranthus

This purple perennial performs particularly well wherever classic sun-loving plants reach their limits. Typical places to use it include:

• north-facing balconies that previously accommodated only foliage plants
• urban courtyards with tall surrounding buildings and limited sunshine
• sheltered entrance areas protected from rain
• window ledges that are too bright in summer but at risk from frost in winter

There is also an interesting extra benefit: the flowers are somewhat similar to sage in both shape and arrangement, attracting bees and other insects. This creates an additional food source in autumn, especially in densely built-up neighbourhoods.

Attractive combinations and potential pitfalls

Visually, the plant is especially effective when paired with contrasting companions. Popular choices include:

• grasses with fine blades for a light, floating effect
• simple evergreen partners such as ivy or small-leaved shrubs
• white or pale pink flowering plants that make the violet colour stand out

If planting very densely, keep an eye on nutrient requirements. Although this perennial is not particularly demanding, it will compete with neighbouring plants for water and fertiliser in small containers. Another common mistake is allowing too much water to remain in the saucer. This can quickly cause root rot, particularly in cool conditions.

For gardeners with limited time, Plectranthus ‘Magic Mona Purple’ offers a combination rarely found on a balcony: minimal maintenance, dependable autumn flowers, intriguing leaf colour – and the chance to turn one plant into a whole collection of new ones with just a few cuttings.