Here’s a good article on garden plants which thrive in the summer heat by the BH&G Garden Editors for Better Homes & Gardens.
Angel’s Trumpet
In full bloom, a good-size angel’s trumpet will stop you in your tracks. The hanging flowers are indeed trumpet-shape and can reach more than 1 foot long, depending on variety. The blooms also release a pleasant, sweet fragrance after sunset. If you have pets or children, just be sure to keep these plants out of reach, because all parts are poisonous if ingested.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: To 6 feet or more
Zones: 7-11
Agave
Though it’s not grown for blooms, agave is a stunning plant that lends an architectural flair to any container. There are striped and solid varieties of agave in different shades of green and blue. Most varieties have extremely sharp leaf tips, so if you have small kids or pets, you might want to cut them off or cover them to make them more friendly.
Light: Full sun
Water: Plant in well-drained soil
Size: To 4 feet or more, depending on variety
Zones: 5-11
Angelonia
This adaptable flower is sometimes called summer snapdragon. Its spikes of purple, white, or pink flowers appear all summer long, no matter how high the mercury rises. Some varieties of angelonia have larger blooms, while dwarf varieties are the perfect size for container gardens.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: To 2 feet tall or more
Zones: 9-11
Bamboo
Although it can be a fast-spreading menace when grown in the ground, bamboo is a dramatic specimen plant when grown in a large container (where it can’t escape). It makes a perfect, fast-growing screen for privacy. When planting bamboo, make the planting hole twice as wide as the root ball; if you’re planting in a container, make sure it’s big enough!
Light: Full sun
Water: Plant in moist, well-drained soil
Size: To 20 feet or more
Zones: 6-10
Banana
With its big leaves, banana makes a great big presence in the landscape. Place the plant in the center of a garden bed, or at the back of a garden against a fence for tropical height. While most are plain green, look for types with a mottling of dark red or white edges for extra interest.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: From 1 to 15 feet, depending on type
Zones: 9-10
Canna
Perfect for creating a lush, tropical look, canna offers large leaves (variegated in many varieties) and glowing flowers in shades of red, orange, yellow, and pink. These plants can often be found close to the water, so they need moist soil to be happy in a garden. You can also overwinter cannas indoors, then bring them outside the next spring.
Light: Full sun
Water: Plant in consistently moist soil
Size: From 1 foot to 15 feet, depending on type
Zones: 7-10
Lantana
Loved by butterflies, lantana produces multicolored flowers in festive shades of red, orange, yellow, pink, and white. Certain varieties have blooms that create an ombre effect, lightening or darkening from the outside in. Some varieties even have variegated foliage that add extra color to your garden even when they’re not in bloom.
Light: Full sun
Water: Plant in well-drained soil
Size: To 2 feet or more
Zones: 8-11
Mandevilla
One of the most regal flowering vines, mandevilla produces large trumpet-shaped blooms in shades of red, white and pink. It’s a fast-growing climber that blooms profusely with clusters of flowers along the vine. Keep in mind that this plant is poisonous if ingested.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: Climbs to 10 feet or more
Zones: 10-11
Passionflower
One of the most beautiful climbing vines, passionflower has intricate flowers in rich shades of almost every shade of the rainbow. Make sure they have a sturdy lattice or a trellis to climb. This is another butterfly favorite!
Light: Full sun
Water: Plant in moist, well-drained soil
Size: Climbs to 10 feet or more
Zones: 6-10
Pentas
Pentas produces clusters of beautiful starry red, white, or pink flowers. No matter how hot it gets, the flowers keep on coming all summer long. (And so do the butterflies that love them!) Their growth habit is neat and compact.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: To 2 feet or more
Zones: 10-11
Plumbago
The beautiful, sky-blue flowers of plumbago are known for attracting butterflies. This shrubby vine is a quick grower and flowers prolifically all summer long. While it can take the heat, it’s also cold-hardy and can be used as a beautiful flowering groundcover.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: Climbs to 10 feet or more
Zones: 5-9
Salvia
A wonderful, heat- and droght-tolerant plant with indigo-blue flowers, ‘Black and Blue’ salvia also attracts lots of birds and butterflies. Salvias don’t do well in cool weather, so be sure to plant them after chance of frost has passed.
Light: Full sun
Water: Plant in well-drained soil
Size: To 3 feet or more
Zones: 5-11, depending on variety
Sky Vine
This fast-growing vine smothers itself with large sky-blue flowers throughout the summer. It’s a favorite of butterflies; adults drink the nectar and some species will eat the foliage. In areas where it doesn’t freeze, sky vine is potentially invasive, so be careful if planting in a tropical area.
Light: Full sun
Water: Plant in moist, well-drained soil
Size: Climbs to 15 feet or more
Zones: 10-11
Solanum
A beautiful shrub, solanum produces clusters of dark violet-blue flowers. This easy-growing plant is often sold on a standard form, meaning trained as a patio tree. You can use this shrub as a living screen for backyard privacy.
Light: Full sun
Water: Plant in well-drained soil
Size: To 5 feet or more
Zones: 9-11
Tropical Milkweed
It’s hard to decide what’s prettier, the brilliant red, yellow, and orange tropical milkweed flowers or the scores of Monarch butterflies they attract.
Test Garden Tip: Monarch caterpillars will eat the foliage of this plant (so don’t worry if you spot a few holes in the leaves). Also, be careful when handling this plant, because the milky sap can irritate skin.
