How to grow and care for mandevilla

What you need to know about mandevilla

Name: Mandevilla (Mandevilla sanderi and varieties).

Height: climbing vine requiring support (trellis or frame).

Foliage: glossy, mid-green, medium to large depending on variety.

Climate: temperate to tropical; not cold tolerant.

Soil: well-drained loam with added organic matter.

Position: full sun; tolerant of light shade.

Flowering: large, sometimes fragrant, trumpet-shaped flowers in shades of white, yellow, pink and red.

Feeding: use a long-term controlled-release fertiliser; don’t over-feed.

Watering: keep moist but not wet; mulch in summer to keep retain moisture.

Appearance and characteristics of mandevilla

There are two distinct types of mandevilla: the lush, glossy leaved, very vigorous mandevilla with big trumpet flowers, and the smaller but equally handsome dipladenia. Today, they are all mandevillas, botanically speaking, but many gardeners still use the two names to differentiate them.

A ‘real’ mandevilla has big, dark green leaves and quite big flowers—up to 10cm or more across—in colours ranging from pure white through startling yellows to flame red and crimson.

The smaller form, dipladenia, has light green leaves and medium-sized flowers up to 5–6cm across. Colours range from white through to pinks and brick red.

All mandevilla varieties produce long tendrils that need to be trained around a trellis or pergola when the plant is young. They do not twine naturally around their supports until they are well established.

Both types produce masses of flowers, making them quite spectacular.

How to grow mandevilla in Australia

• Mandevilla is generally grown by specialist nurseries as a named variety. A quick check of the label will show you the colour and tell you any other important information.
• Mandevilla is frost tender, and does best in a temperate to warm climate. Dappled sunlight with shade during the hottest part of the day and a moist, rich soil that drains well are best.
• Before planting, add compost and well-weathered manure to the soil and dig it in. A mulch of sugarcane or pea straw spread around the main stem, but not touching it, will help keep the soil moist. Add a dressing of manure or compost every winter to enrich the soil.
• Large mandevillas need a permanent trellis on a fence or pergola, or a garden arch to allow them to climb. The smaller types can be trained on a lattice or against a fence. While the large-flowered vines are generally too vigorous to be grown long-term in pots, the smaller types make excellent container plants, and can be grown on a verandah or terrace for many years. Top up the potting mix each spring, and regularly trim back the long tendrils to encourage a bushy habit.
• Use a large pot—a half wine barrel is excellent—and premium-quality potting mix. Place a fan-shaped trellis in the back of the pot for training the vine.

Watering mandevilla

Mandevilla enjoys moist but not wet soil—water often during warm weather. Plants in pots need to be watched carefully because they can dry out very quickly. Water these in the early morning and repeat again late afternoon if necessary. Try to avoid wetting the leaves, because direct sun through droplets can disfigure them.

Fertilising mandevilla

Mandevilla is quite vigorous, but that doesn’t mean it should be overfed. Too much fertiliser can cause excessive lush growth at the expense of flowers. Use a controlled-release fertiliser twice a year in spring and late summer at the recommended rate. To keep your plant flowering well, use a liquid or water-soluble bloom booster fertiliser at full strength every 4–6 weeks from mid-spring through to mid-summer.

How and when to prune mandevilla

Mandevilla needs pruning yearly to keep it reasonably tidy and to encourage flowers, which are produced on new growth. Cut vines back by about half in winter, making each cut just above a pair of leaves.

Long tendrils can also be trimmed back during the warmer months, but don’t be too severe, as this could result in fewer flowers.

Always wear gardening gloves when pruning mandevilla—it exudes a milky sap, which can irritate the skin.

Diseases and pests

Aphids can be troublesome on juicy young shoots of plants, but a spray with pyrethrum will soon dispatch them. Repeat again in a couple of weeks if necessary to mop up any new hatchlings.

Scale may also be present over summer. A horticultural oil (‘white’ or pest oil) applied to all leaves and stems is usually effective. Make sure the undersides of leaves are treated too.

If you like this then try

Frangipani: a tall, warm-climate shrub with highly scented flowers ranging in colour from white to deep cerise.

Poinciana: flame Tree, with brilliant red flowers and fern-like foliage; prefers a tropical or sub-tropical climate.

Poinsettia: grows outdoors in warm climates; produces bright red through pink to cream showy bracts.

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