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My appraisals for this column are for annual flowers and tender perennials grown as annuals that weather the siege and thrive in spite of the difficulties.
It is important to distinguish between heat tolerance or the plant’s ability to tolerate high temperatures and drought tolerance, which is the ability to use less water.
Some plants are able to tolerate both conditions and still thrive. As you select flowers, group those with similar requirements together to maximize the tolerance to one or both of these conditions.
Lisianthus or Eustoma grandifloru, is a flower that has been around for a long time but plant breeders are adding new varieties to the garden palate. The plants grow 12 to 18 inches high and have many fragrant cup shaped flowers on each stem.
These flowers are outstanding performers even with the heat and drought. The flowers are fragrant and the colors are ivory, pink, or several shades of purple and blues. They grow well in containers or in mixed beds and make excellent cut flowers.
Gazania or Gazania rigens grows 6 to 12 inches high and is covered with fragrant daisy looking blossoms. The flowers are usually yellow and orange but newer shades include lavender, red, or muted pink.
They thrive in the full sun and bloom throughout the season until they freeze. These plants work well as mass plantings, borders, containers and mixed plantings. The flowers are both heat and drought tolerant.
Joseph’s Coat or Amaranthus tricolor is also know as summer poinsettia. The plants grow 1-6 feet high and will make a real showstopper in the garden. Grow them for their highly colored leaves that are ablaze with shades of red, orange, purple, gold, or lime.
The reason this plant is so heat and drought tolerant is because it is an ornamental pigweed. Fortunately, it does not seed like its wild cousin and it is very colorful all season. Use it for mass planting or for a tall background.
Vinca or Catharanthus roseus is about as close as you can get to a showy heat and drought tolerant annual groundcover for Utah. The plants grow 4 to 18 inches high and have white, pink, lavender or red blossoms. They tolerate full sun to partial shade and bloom from planting until frost. In addition to the groundcovers use, they are excellent for mixed borders and containers.
Dwarf Morning Glory or Convolvulus is a cousin to field bindweed or wild morning glory. It does not have the perennial underground root system so it is safe to grow in your gardens. It reaches a height of 12 inches and has very bright blue, pink, or purple flowers.
Grow the plants in full sun for blossoms from summer through fall. It is excellent for rock gardens, walls, edging, and containers. The one drawback to this plant is susceptibility to spider mite infestations.
Snow-on-the-mountain or Euphorbia marginata is one of the most heat and drought tolerant plants I know of. It grows 2-3 feet high and has white flowers. Grow it in full sun in beds, borders and mass plantings.
Globe Amaranth or Gomphrena globosa is a partially dried flower that is excellent for cutting or drying. The plants reach 18 inches high and have globe or strawberry shaped blossoms of white, pink, purple, orange, or red. Grow it in full sun and it will bloom from summer through fall.
Sunflower or Helianthus is a versatile heat and drought tolerant plant. If you think that the common sunflower and the seed sunflower are the only choices, think again. These plants have been revolutionized by plant breeders and grow 2-15 feet high with white, yellow, gold, or red flowers. Grow them in full sun or light shade as borders, screens, fences, or in containers.
The true morning glory family is not the same as our wild morning glory or field bindweed mentioned previously under Convolvulus. There are several very heat tolerant annuals in this group. They must have regular watering to thrive so they are not highly drought tolerant. They are all vines and will grow from 3- 15 feet depending on the height of the trellises.
Moonflower Vine or Ipomoea alba has large white flowers that bloom in the evening, giving it the common name. Use it on a trellis, fence or arbor and around patios, porches, and outdoor dining areas. Ipomoea purpurea grows like the moonflower vine with purple, red, white, violet, blue flowers. These showy flowers open each morning and then close that night and do not reopen.
Another Ipomoea is Sweet Potato Vine or Ipomoea batata. These very showy plants are grown for their foliage, not for their flowers. They tolerate sun to partial shade and are excellent for baskets and containers and as ground covers. Blackie' is a dark leafed cultivar, 'Tricolor' has shades of pink, cream, green and 'Chartreuse' is lime-green.
Moss Rose or Portulaca grandiflora is the final selection on my list only because of space not because they are not more flowers to feature. It grows 6 inches high and has brilliant pink lavender, pink, yellow coral or white blossoms. Plant it in full sun and do not overwater it.
