Summer in Mississippi means heat and humidity.

And, low rainfall this year is making the weather even more daunting and is adding stress to shrubs and trees that normally are unaffected by the summer heat. Savvy gardeners may notice that some plants are handling the heat and drought conditions better than others. A few old-time favorites deserve consideration for our modern gardens.

Altheas or Rose of Sharon used to be a standard landscape shrub in gardens throughout the South. These drought-tolerant shrubs bloomed in shades of pink, lavender and white in late summer when almost nothing else showed much color. Thomas Jefferson planted them at all of his homes — Shadwell in 1767, Monticello in 1794 and Poplar Forest in 1812. They were prominently listed in Southern nursery catalogs long before the crepe myrtle became popular.

“Altheas, in all their forms, are still supremely adapted to today’s gardens,” wrote Bill Welch in “The Southern Heirloom Garden.”

The late Dr. Donald Egolf of the National Arboretum in Washington, D.C., well-known for his work in developing the mildew-resistant strains of crepe myrtle, also worked extensively with altheas. He is credited with the development of modern sterile triploid altheas which produce earlier, larger flowers without the problematic seeds of earlier types that sprout and become invasive.

There is a renewed interest in Rose of Sharon with new selections making their way into the marketplace, says Tim Woods of Proven Winners, one of the largest U.S. plant growers.

The Egolf altheas — Diana (white), Helene (white with a maroon throat), Minerva (lavender) and Aphrodite (pink) — are becoming more available. They tolerate extreme heat, drought and poor soil but do best in dirt with moderate fertility and moisture. Growing 8 feet to 9 feet tall, they can be trimmed into small trees or used as specimen plants or for hedges in home gardens, parks, industrial complexes and mall landscaping.

Breeders in France, England, the Netherlands and South Korea are busy developing cultivars that are making their way into American production. One is a dwarf cultivar called Little Kim that will be ideal for small patio and container gardens. There is also a Chiffon Series and a Satin Series with several cultivars in each.

Oleander is another old-favorite that blooms in the hottest weather conditions. A native of Asia and the Mediterranean, they were favorites of the ancient Greeks and Romans. They are so heat tolerant that they have been used in median plantings along Texas highways near Galveston and San Antonio.

Jeff Richardson, the city’s landscaper, used white oleanders in a city planting along Halls Ferry in Marcus Bottom.

Oleanders are large, multi-stemmed shrubs bearing cream, white, pink or red blooms spring through summer. Mature plants tolerate heat, drought, wind and salt, making them popular in coastal areas. They are easy to grow with few insect and disease problems.

Vitex or Chaste tree is another heirloom shrub with profuse purple to pale pink blooms in early summer. If spent flowers are trimmed off, it often re-blooms in August. This bee and butterfly favorite is grown as a large deciduous multi-stemmed shrub.

Steve Bender, co-author of “Passalong Plants,” said he can’t understand why these are not used more frequently in Southern gardens — they are drought tolerant, not fussy about soil and have few disease or insect problems.

Vitex looks best if old wood is removed in winter and the previous year’s growth is cut back by several feet.

Southern heirloom plants belong in Southern gardens for three reasons, Welch says — they are tough, they are pretty and people don’t save ugly plants.

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Miriam Jabour, a Master Gardener and Master Flower Show judge, has been active in the Openwood Plantation Garden Club for over 35 years. Write to her at 1114 Windy Lake Drive, Vicksburg, MS 39183.