How to grow mandevilla

Bear in mind that mandevilla is toxic to dogs and cats, and can lead to stomach upset, nausea and vomiting if ingested.

How to grow mandevilla

Grow mandevilla in a sunny, humid spot such as a heated greenhouse or conservatory, in free-draining soil or a large pot of loam-based compost with added grit to aid drainage. Train it up a trellis or obelisk to make the most of its fragrant blooms.

Where to grow mandevilla

Humidity is key to successfully growing mandevilla – spring conditions should be humid with an average daytime temperature of 21ºC and a nighttime temperature no lower than 18ºC. Winter temperatures shouldn't fall below 15ºC. The best places to grow mandevilla are conservatories and heated greenhouses, where conditions best mimic their natural tropical environment.

If possible, grow mandevilla direct in the soil of a greenhouse or conservatory border. Being a large, woody climber, it can struggle in pots.

How to plant mandevilla

For best results, plant mandevilla direct into the greenhouse or conservatory border, adding horticultural grit to the planting hole to aid drainage if necessary. Dig a hole slightly larger than the rootball, then place the plant in the hole, ensuring that it's at the same level it was in the original container. When you're happy with the planting depth, backfill with the potting mix, gently firm the soil around the plant and water thoroughly.

If planting in pots, choose as large a container as you can afford and use a loam-based compost such as John Innes No.3. Add horticultural grit to aid drainage.

After planting, choose three to five stems to make a permanent framework, which you can tie to your support. You will use this framework to prune around each year.

Caring for mandevilla

In spring and summer, water regularly and apply a monthly liquid feed in summer. Reduce watering in autumn and winter, and then increase again from spring. Mist daily in summer to increase humidity.

Pruning is essential to manage the size of mandevilla plants and promote healthy growth:

• If there is only one main shoot, trimming its length by one-third will stimulate further growth from the base – ideally, you want three to five main shoots to create a permanent framework that will make pruning easier in the long term.
• Remove overcrowded or weak shoots to maintain a compact and tidy appearance.
• From late winter to early spring, spur prune stems by cutting back side shoots to within three or four buds of the permanent framework. This will encourage the development of flowering wood. Avoid pruning in winter, as this can weaken the plant.

Propagating mandevilla

Mandevilla can be propagated by softwood cuttings or seed.

From cuttings:

• Take a 15cm cutting from a healthy stem and remove the lower leaves.
• Dip the cut end in rooting hormone and plant it in a moist but free-draining potting mix.
• Keep the cuttings in a lidded propagator with a bottom heat of 20-25ºC.
• Cuttings should start showing signs of growth after around a fortnight. Pinch back the new growth to create a bushier habit.

From seed:

• Soak mandevilla seeds in water for approximately 12 hours before planting.
• Sow seeds in moist, free-draining compost and cover lightly with more compost.
• Place in a lidded propagator with temperatures ranging between 18-23ºC.
• Pot seedlings into individual pots once there are are least two pairs of leaves per plant.

Pests and diseases

Mandevilla can be susceptible to pests such as aphids, mealybugs and spider mites. To deal with these pests organically, you can use insecticidal soap, following the instructions on the packaging. Signs of infestation include discoloured leaves, sticky residue and visible pests.

Mandevilla varieties

Mandevilla 'Fuchsia Flammé' – bright-pink flowers over a long flowering period. Height x Spread: 7m x 50cm

Mandevilla ‘Bloom Bells Red’ – crimson blooms over a long flowering period. H x S: 1.8m x 50cm

• Buy Mandevilla ‘Bloom Bells Red’ from Van Meuwen

Mandevilla sanderi ‘Bloom Bells White’ – bright white flowers against a backdrop of glossy, dark foliage. H x S: 1.8m x 50cm

• Buy Mandevilla ‘Bloom Bells White’ from Dobies

Mandevilla ‘Sundaville Flamingo Pink’ – unusual flamingo pink blooms. H x S: 1m x 50cm

• Buy Mandevilla ‘Sundaville Flamingo Pink’ from Thompson & Morgan