Horticulture Magazine

Mandevilla ‘Rock Trumpet’ Plant Care & Growing Tips

white mandevilla on a garden wall

Mandevilla Overview

Official Plant NameMandevilla
Common Name(s)Dipladenia, Rock Trumpet, Chilean Jasmine
Plant TypeClimber / Houseplant
Native AreaAmericas
Hardiness RatingH2/H3
ToxicityToxic
FoliageSemi-evergreen climber
FlowersLarge, showy flowers
When To Sow (Indoors)April, May
Flowering MonthsMay, June, July, August, September
When To PruneMarch
Sunlight

Preferred
Dappled / Partial Shade

Exposure
Sheltered (Indoors)

Size

Height
1 – 2M

Spread
0.1 – 0.5M

Bloom Time
May – October

Soil

Preferred
Loam

Moisture
Moist but well drained

pH
Neutral / Acidic

Mandevilla, were previously named Dipladenia, but are probably better known as ‘Chilean Jasmine’ or ‘Rock Trumpet’.

They are named after Henry Mandeville, an English diplomat and botanist. Mandevilla are usually climbers with showy, sometimes scented, flowers opening in the summer. However, they originate from warmer climates and are thus tender and are happiest grown in a conservatory or greenhouse here in the United Kingdom.

What are Mandevilla plants?

Mandevilla are perennial climbers that originate from Central and South America. They are stunning ornamentals that can have red, yellow, pink or even white flowers that are often scented and can bloom for months on end during the summer.

close up of pink flowering Rocktrumpet in the garden
Pink flowering Rocktrumpet

Flowers are produced on the current year’s new growth and it is important to provide the right warm and humid conditions for the new shoots to grow to produce blooms later in the year.

Varieties that are commonly available here in the United Kingdom include: Mandevilla sanderi ‘Bloom Bells Pink’ (H1.5M x S1M), Mandevilla laxa AGM (H2.5-4M x S1-1.5M) with creamy white flowers and Mandevilla boliviensis AGM (H2.5-4M x S1-1.5M) with white and yellow flowers.

It is important to note that mandevilla plants are considered toxic and care is required if pets and children are present.

Mandevilla is a great climber, with an exotic feel and easily grown in a pot. It can be a great addition to a conservatory or even an outside terrace, but only during the warmer months.

How to grow mandevilla

Mandevilla are most commonly grown from small plants available from local plant nurseries or online. They need indoor protection during the colder months and prefer full sunshine, although will need shading from the hot midday sun.

woman tending to mandevilla plants in a greenhouse
Indoor conditions such as a conservatory or greenhouse are preferred

Mandevilla are tender plants and need to be kept over winter in temperatures above 10C and during spring require a humid and warm environment with temperatures of 18C at night and 21C during the day. However during the summer months they can be placed outdoors in a sheltered and sunny spot.

Mandevilla can be grown from seed in spring, but will need the warmth of a propagator to get them to germinate, or grown from softwood cuttings taken in early summer. If taking cutting, new growth must be selected and in order to take root will need the bottom heat of a propagator.

Where to grow

Mandevilla prefer full sun and a sheltered spot to grow well and produce the wonderful blooms they are known for. They are most commonly grown in pots so they can easily be moved depending on the seasons. Due to their temperature requirements they are often grown in a conservatory or heated greenhouse and only placed outside during the warmest months of the year.

Supports 

Supports are required for the climbers to grow up. Bamboo canes forming a tripod are often provided in the pot when bought, but in time and depending on space a taller support will be required. Longer term, metal climbing supports such as obelisks are ideal as they will not rot over time and provide a strong frame for the plant to grow upon.

rocktrumpet plant with red flowers growing up a garden obelisk
Support from an obelisk will help your plant grow skywards

Caring for mandevilla

To plant mandevilla fill a pot with a free draining, soil based compost such as John Innes no.2 and plant at the same depth as previously planted. The shoots will need tying in to begin with and the tops can be pinched out to promote bushier growth if required. During the growing season mandevilla will need watering and feeding often, they do not like to have wet roots so make sure there is adequate drainage. During the winter months, growth will slow and the plant will need less moisture so reduce watering and cease feeding until spring.

Mandevilla are grown for their flowers which are only produced on new growth, thus it is important to care for the plants during spring when the plant begins growing again after winter.

It is recommended that mandevilla are re-potted each spring with fresh compost and a larger pot as required.

Pruning

Depending on the variety mandevilla can grow to 4.5M tall. However, Mandevilla sanderi will usually grow to no more than 1.5M and thus might be a better size if pot grown and moved around depending on the seasons. Mandevilla are classed as pruning group 12 and require pruning in late winter or early spring before any new growth appears. To prune, cut back the lateral shoots to 3 or 4 buds from the main framework and cut back any vertical shoots out growing the supports. The white sap produce when cut is an irritant and gloves must be worn when handling to avoid irritation.

Common diseases and problems

Mealybugs

Mealybugs are insects that feeds of the sap of house and greenhouse plants, including mandevilla. They leave a sticky honey dew behind them and can weaken the plant and lead to leaf drop if not dealt with swiftly. Mealybugs like warm conditions and are hence  rarely a problem outdoors. The telltale sign of mealybugs is a white fluffy residue left on the leaves and in the leaf joints. Mealybugs do not mean the plant is destined for the compost pile, but can easily be dealt with if quick remedial action is taken. Firstly remove the affected plant from any others to avoid any spreading and contamination. Wipe away any sign of mealybugs from the plant using a wet sponge or baby wipe and remove any damaged leaves which may harbour eggs. Ladybirds like to eat mealybugs and their eggs and can be introduced during the summer months as a non pesticidal approach.

Pesticide control can include spraying the affected plant with plant oils, fatty acids and natural pyrethrum. Insecticides including cypermethrin and deltamethrin can also be used but care must be taken not to apply when the plant is in flower to prevent any danger to local pollinators.

Mealybugs don’t travel far without help and infestations are usually brought in on new plants. To avoid potential infestations newly obtained plants can be quarantined away from other plants for a few weeks prior to joining the others.

Why is my mandevilla not flowering?

Mandevilla need the correct pruning regime, seasonal environment conditions and nutrients in order to flower. It is important not to prune the plant any later then spring as the new growth and subsequent blooms may be pruned off accidentally. Flowers are produced on new growth and thus it is important to make sure that the conditions are correct for the new shoots to appear. The correct temperature, soil kept moist, but not wet and feeding the plant from spring onwards should help encourage the flowers to bloom.

pink Mandevilla sanderi flowering in summer
Ensure you’re facilitating the right conditions for trumpet-like flowering

Why are the leaves falling off?

Mandevilla are semi-evergreen and may drop some leaves during the winter months, this can be seasonal and nothing to worry about. However, if leaves are dropping during the summer then check you are not over or under watering the plant and that there are no obvious pests, such as mealybugs on the plant.

© 2021 TKO DIGITAL LTD | Registered in England and Wales No. 10866260 | This website uses cookies. Read our privacy policy.