Mandevilla laxa (Chilean jasmine) is a delicate deciduous creeper with sweetly-scented white flowers.
If your pergola, trellis, garden arch or wire fence is still bare because you can’t decide what evergreen flowering creeper or vine to plant, then pause here, because you can’t go wrong with the magnificent mandevilla. Once planted, for much of the year it will treat you to beautiful clouds of bright pink, trumpet-shaped flowers. Gardeners who have been around for a while may remember using earlier varieties of this plant, particularly for training up the concertina-like trellises that were used as features on sunny suburban verandas, or to screen off unattractive sights such as the washing line. They were called dipladenias in those days, from the botanical name Dipladenia splendens, which has since been relegated in favour of the name Mandevilla splendens. Plant breeders have been really busy with the genetic material from this exotic genus, and out of their efforts have come the prettiest and the best creeping and semi-creeping plants for large gardens with arches and pergolas, and small gardens where these treasured plants find homes in pots.
When do they bloom?
Expect blooms throughout the year in some of our temperate climates, and through summer and deep into autumn in colder climates.
Most suitable climate
They can tolerate light frost in the temperate summer rainfall regions and in the Highveld, but it would be safer to plant them in sheltered areas or in pots, and to protect them with frost cover. They flourish in subtropical gardens, but can suffer from wind damage if planted in gardens very close to the coast. In drier regions with cold winters they will need to be planted in a completely sheltered area and they will need water more regularly during summer. In the winter rainfall regions of the Western Cape they can sometimes be semi-deciduous, but they still deliver a breathtaking performance in summer and deep into autumn.
What they need
Location: full sun or light shade (such as morning sun and afternoon shade). Mandevillas don’t like stifling-hot places, walls that reflect heat, or poor air circulation. They are happiest on sturdy, freestanding structures such as trelliswork, garden arches, fences and gazebos, and they need supporting wires or a framework to grow along.
Soil: well-drained loamy or sandy soil, enriched with compost and bone meal, ensures a healthy root system. Heavy clay or poorly drained soil that stays damp for long is not suitable. Where these conditions prevail, rather plant mandevillas in pots using a good quality commercial potting soil.
Water: they do not need excessive quantities of water, but do need to be watered regularly during summer – although only when the soil in the garden or pots has dried out considerably.
Fertilizing: you expect loads of flowers so the plants must be fed in spring and again in late summer with potassium-rich granular fertilizer. Give those growing in pots a monthly application of liquid fertilizer in addition to the granular fertilizer.
Pruning: woody or sparse plants can be pruned back in spring to encourage new growth. A severe pruning every four years, taking the plant down to knee height, does no damage and encourages dense growth. In summer, when semi-creeping mandevillas in pots are growing actively, you can pinch off the growth points to encourage more side stems to form.
Watch out for this
* During very dry and warm weather, mandevillas are sometimes plagued by aphids and red spider mites. Light infestations of either of these pests can be washed off the plant using a strong jet of water from a hosepipe. If the problem worsens, consider using an insecticide.
* Plants losing leaves during summer can be a sign of either too much or too little water. During winter (especially in cold temperatures, or areas with high winter rainfall), it is quite normal for the plants to be semi-deciduous.
* The root system of the mandevilla doesn’t like to be disturbed, so ensure that there is very little or no digging around the plant.
In a nutshell
* Like sunny growing conditions and good air circulation.
* Sturdy freestanding supports preferred, avoid hot walls.
* Grow rapidly and bloom from a very young stage.
* Ideal for colourful vertical gardening.