Mandevilla competition


Hello, I’ve been growing Mandevilla on my south-facing, mid-town Toronto balcony for five or six years now, and am curious about the following: Most summers when I have grown the Mandevilla by itself in a pot (starting it as a small, 6″ to 12″ plant from the garden centre), it has flourished, reaching as much as two or three feet in height (see photo). But whenever I have included smaller plants in the same planter around the Mandevilla’s base (e.g. Ivy, Creeping Jenny etc., to add visual interest), the Mandevilla hardly increases in height, although it stays fairly healthy throughout the season with lots of blooms. I’ve noticed large and attractive planters containing Mandevilla as the “centrepiece” in public places around the city, also with ivy, Creeping Jenny and much more around the base, but with very tall and flourishing Mandevillas! What could be causing this “height challenge” in my balcony planter? Is it possible that these “filler” plants somehow “compete” with the Mandevilla for the nutrients in the soil? And if this is the case, should I just remove those plants and let the Mandevilla have the whole planter to itself? Or is there another approach I could take?

Thank you for your assistance and best regards,


Thanks Susan, for reaching out to the Toronto Master Gardeners. I have been pondering this question and am not sure that  I  have a proper answer for you. You seem to have good experience with growing these plants.

It made me look at my own container gardening with Mandevilla where  I do  plant companion plants. The Literature suggests a variety of companion plants so that would not be the issue here, I don’t think. I too had been wondering if this year they were slow . The one in the most sun of course is growing faster than the ones in shorter sun time.

The markets are flooded with Mandevilla this year more than ever it feels. Could something have changed in the breeding for which I have no knowledge? Do you change the soil in the pot every year or so? Do you fertilize on any schedule? Any change in your watering schedule?  Weather always can play a role in plant changes. We had a span of good heat, and then it dropped to quite cool for a while. This may have affected the growing tips of a tropical plant. Have you checked the tips of the growing vine for viability? Cut back to growth if you see it is soft or dying.

Like you I love the vine of colourful flowers but we might need to be patient to watch it grow over the summer. Keep the companion plants.

July 1, 2021