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The Charleston Gardener: Summer flowers: here comes the sun (and the humidity)

By Louisa Cameron

The unique bloom of the mangave, a sun-loving temperennial succulent. Images courtesy of the author.

Until we cut back overhanging crape myrtle branches, had a crew help us dig up a maze of roots in the flower beds beneath them, added bags of compost to the bed and got rid of most of the weedy perennials that were just barely hanging on, we could never get our southern exposure border to look anything other than tired in the summertime. Larkspur saved the look of the beds along our 100-plus-foot brick wall from late spring through early June but needed to be pulled out as the plants dried up and went to seed. Very few spring annuals such as pansies, snapdragons and sweet alyssum survived past the third week in May. The roses gave up blooming until the fall, and the digitalis looked pitiful and had to be pulled out along with everything else.

Tough stuff

Then I found butterfly weed (asclepias) plants in red, orange and yellow at a nursery in the Upstate while visiting family, brought them home and have had great success with them in the middle border where they grow to about three feet. They reseed, are good cut flowers and are steady summer bloomers. I cut them back as I deadhead or pick flowers for arrangements and cut them back again when they have finished producing seed in late summer, so they do not take up much room in the fall. Last year, just for fun, I planted tithonia, the Mexican sunflower, at the very back against the wall. Not only did these sturdy plants grow about seven feet tall and produce masses of brilliant orange flowers, but they also reseeded with a little help from some of the seeds I saved and scattered, and are coming up this late spring of 2022.

Other summer volunteers are one or two happy dwarf sunflowers and some zinnias. The bright chartreuse sweet potato vine is an excellent ground cover or climber that does not bloom but spreads quickly and usually comes back each year. It is easy to transplant and can tolerate some shade. Tall pale-green stems of loosely clumped plumbago peek out from between our Italian cypresses with their soft-blue round flower heads, providing contrast in color and texture. Perennial Plumbago auriculata came to Charleston by way of South Africa and is a reliable addition to any sunny spot. Golden Thryallis (Galphimia gracilis) is a fast-growing new addition to a dry spot that gets sun, though not the full sun it would appreciate. So far, I have been able to keep it in bounds, and although it could be more floriferous if planted a few feet farther south in the garden, it is drought tolerant and has many small seedlings sprouting around its base that I will pot up to try in the “hot” bed. It is a native of Mexico and has soft dark-green leaves and clusters of small chrome-yellow five-petal blossoms. The stamen turn red as the flower opens.

A couple of years ago, a friend gave me a few small pots of aloe. These have grown into large plants that have been showy since March. Three- to three-and-a-half-foot-thick stems with pinky-orange clusters of tubular blossoms at the top have continuously been emerging from mottled green rosettes of spiky succulent leaves. They multiply quickly, and we have been dividing them and spreading them down the border. Aloes are tough, and we have two as-yet-not-positively-identified relatives in pots in full sun that have also done well. They are either mangaves or manfredas. The mangave is a cross between an agave and a manfreda and seems to be high up on the list of currently popular plants. Last year was the first time they bloomed, and they are gorgeous. Ours have been in their pots for several years, and they finally sent up a four-foot rod-straight spike with small burgundy flowers at the top that look somewhat like sparklers. There is a smorgasbord of them for sale on Etsy.

Tithonias and sweet potato vine.


Next to the aloe, lavender-flowering Tradescantia pallida, a spiderwort, flourishes and spreads over the warm brick borders and adjacent flagstone pads that are in front of nearby benches. This particular spiderwort has dark-purple fleshy leaves and makes an excellent midheight groundcover. It also adds deep contrast and texture in the front of the border and mixes nicely with other plants. I have it next to a pink Noisette rose called Natchitoches that blooms for months and wants to grow at least six feet tall, but I keep this particular rose severely pruned so it will stay in scale. We let it grow unheeded until it has finished blooming in other parts of the garden. It doesn’t seem to mind being pruned. It is a “found” rose that had been blooming by a grave near a fort in Natchitoches, Louisiana, for more than 100 years, according to the Antique Rose Emporium. I don’t know if the wind blows the seeds through the garden or if the birds deposit them as they roost, but we have several small plants in odd places that we are nurturing until winter, when we can move them without too much trauma.

Several kinds of marigolds, phlox, lantana, nasturtiums, petunias, verbenas, cosmos and zinnias will also provide summer blooms, and most will reseed or you can collect seeds from ones you let fully mature and don’t pick for bouquets. I cast the zinnia seeds in late April without raking them into the soil, but there is a new technique I want to try: Mix lots of seeds in a container filled with potting soil and place the mixture where you want the seeds to germinate.

Lantana is a wonder plant. It spreads all over the garden, partially due to the birds that drop the seeds, and it comes in a huge variety of colors. It’s easy to make topiaries from a single-stemmed plant. I first saw large “lollipop” versions of trained lantana at historic Paca House in Annapolis, Maryland.

I allow cherry tomatoes to spread out because they are so delicious that many we pick never even make it to the kitchen and I so enjoy the smell of the leaves. The orange/yellow variety whose tag I lost (I think it may be “sungold”) is sweet as sugar. I read that tomatoes thrive and produce more fruit with a few doses of “banana water” made by letting a banana peel soak in a large jar of water overnight or all day. Last year I fed my plants with this every week, and they definitely produced a better crop.

We tucked a few heat-loving bougainvilleas in corners and on arbors for a gorgeous hot pink show in midsummer. They are vigorous and need pruning and also a little protection from a freeze. Mixed in with all the above are a couple of dozen daylilies that I ordered from a farm just down the coast. They were small divisions but have thrived in spite of some rust and aphids. I am constantly debriding dead leaves from around the base of the plants, and I try to remember to pick off the dead blossoms every day. There are some striking reds that are my favorites at the moment.

Speaking of striking, one of my absolute favorite plants that appears every year is the gloriosa lily, Gloriosa rothschildiana. It is a knockout. The center is chartreuse ringed in bright yellow, and the six long petals spreading out from the center are deep red, sometimes edged with yellow. The bloom turns inside out as it matures in a day or two, and the petals become narrower, giving it a slightly different but fantastic shape. Gloriosas come up where they please, as they move about by tuber and seed. These lilies are strong climbers and clamber up our lemon trees, tea olives, figs and roses. It took me several years to get them established, but now they are in numerous spots throughout the garden — except on the arbors where I would like them to take over for the summer and twine up the spent climbing roses. The Alstroemeria lilies that I brought into the garden decades ago continue to spread deeply around the bases of the shrubs in the beds, and I don’t think we will ever be able to get rid of them. At least they make great cut flowers. I offer them to anyone who will dig them and take them away.

Be careful with these hardy spreaders

Ruellia (Mexican petunia) is one of the most persistent late spring and summer blooming plants in our garden. It doesn’t care much where it grows but it loves the sun. I had to move it out of the main beds and put it in a narrow bed where it cannot move much, and I keep a beady eye on it now.

Vines can quickly get out of hand. I have crawled under the big azaleas and dug out the sweet autumn clematis, but it comes back to quickly cover the tops of the shrubs like a net cast where it can catch the sun. Wisteria should not even be mentioned. Unless you like it to ramble and scramble and choke everything in its path, I would not plant it except in a metal container, over a structure that needs hiding or on a strong support where you can reach it for pruning. It takes a lot of heavy pruning to keep it under control. It took years to get akebia (chocolate vine) and cashmere bouquet eliminated from the garden, but we still have wisteria vine pop up in the bamboo that has also lived in the back of our property for more than 40 years.

Soft ferns (I think they are Christmas ferns) that grow up to three feet have spread too quickly in dense colonies during the past year, and I have had to thin them again and again along with the dwarf umbrella plant that is vying with the creeping daisy (wedelia) to take over the garden, but all three are excellent for covering areas where it is difficult to grow much of anything else. The ferns are sun tolerant but prefer shade.

Recommended reading

The plants mentioned above are just suggestions for what is currently working (or not working) in our summer garden. My friend P. J. Gartin wrote two delightful books on plants that are heat tolerant: Some Like It Hot and Some Like It Hot Flowers are two of my favorite reference books for Charleston. These books have an extraordinary amount of information in addition to the color photographs. Not only are there scientific charts, heat and humidity and frost and zone maps but also many recommendations for using ornamental grasses, tropical plants and plants with interesting foliage and leaves, along with instructions for sowing seeds both inside and outdoors. These books cover many topics and are full of exhaustive horticultural advice. Of course, the wonderful growers who supply our local nurseries are always coming up with new plants for our region that have been in the testing phase for years.

Louisa Huger Pringle Cameron is a native Charlestonian married to Price Cameron, a retired plastic surgeon. She is the author of three books on the gardens of Charleston, enjoys duplicate bridge and is a proud grandmother of three.


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