Dipladenia and mandevilla are a popular tropical flowering plant known for their fantastic display of colour all summer long. Both are native to South American rainforests - and as a result love the hot weather of our summer months here in Southwestern Ontario. There are two main characteristics when determining if a plant is a mandevilla or a dipladenia. The easiest difference is the growth habit. Mandevilla are more of a vining plant that climbs upward. They are almost always sold with a trellis in the pot for the plant to be trained upward on. Dipladenia are fuller and more bushing. They do have some vines that grow, but they have a downward habit. When the plants are small and haven't started growing much you can determine them also by the size and shape of their leaves. Mandevilla have a broader leaf and dipladenia a leaner and more pointy leaf.
Regardless of whether the plant is a dipladenia or a mandevilla, their care is the same - both require sunshine and heat!! They will grow best when placed in full sun or very very bright indirect sun, and won't really start to bloom much until the overnight temperature stays above 18°C or 65°F. Once these beauties get growing they are a stunning display of colour and very easy to care for. They do best if you allow the top couple inches of soil to dry out between waterings and will bloom prolifically if fertilized every couple of weeks with a water soluble fertilizer that promotes blooming. They are very easy to care for and a sure winner every year!
In southwestern Ontario mandevilla & dipladenia are most often grown as an annual and discarded when the temperatures turn too cold for them. However with a bit of effort it is also possible to winter them over in your home. Dipladenia and Mandevilla have a natural dormant period from October to April. There is almost no growth during this time. It is normal for most or all of their leaves to fall off. Due to this it is most popular to winter them over in a cool/dark area of your home and bring them back out as spring arrives. In the fall before they get frosted trim the plant back until there is only 6-12" of plant remaining ... this will vary based on the maturity and size of your plant. Make sure there is some moisture left in the soil in the pot and place it in a cool dark spot to wait out the cold winter months - if a cool basement space isn't available a garage may work as well, as long as the temperature stays above 7°C all winter long. Check the pots periodically to make sure the soil hasn't completely dried out, but only water sparingly if it has. Keep in mind there is no active growth, so the plants need very little water. Do not fertilize them during their dormant period.
In mid-late March bring your plant out of its cold storage and place it in a bright window -- ideally south facing - and give it a bit of water. It may take several weeks for it to start showing signs of growth. The plants need to be kept indoors until all risk of frost is past. If there is no cold storage available they can also be grown as a houseplant. Before bringing them into your home inspect the foliage for any bugs and treat as need with an insecticidal soap. The vines may still drop their foliage even when placed in a bright window as this is a normal part of their dormancy. Water your plants as needed -- making sure to allow the top inch or two of soil to dry out between waterings. Resume regular fertilizing once the weather has warmed up and your dipladenia and mandevilla are growing outdoors.
For a video demonstration check out our YouTube video: