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Feel the Burn

Bill Calkins

Hot and humid. Hot and dry. No matter how the weather reporter or locals describe summer weather in Southern climates, we all know it’s hot, plain and simple. Plants also know it’s hot, and for many, performance is less than desirable. Thankfully, not for all of them.

Here’s a solid list of a dozen annuals and perennials that can take the heat and keep on thriving. Some are classics—old standbys that have been upgraded over the years through ongoing breeding—and others are newer to the market, but trialed and tested in hot climates.
You most likely have a go-to list for best performers in hot climates, but perhaps it’s time to add to it or change it up a little bit going into 2022.

Angelonia is a species that continues to evolve quickly, with new breeding and different attributes coming to market every year. There are leading varieties from seed and vegetative propagation, and different series run the gamut from spreading to upright and smaller-flowered to huge flowers, with an impressive color range of solid and bicolors.

Landscape growers have seen excellent heat performance from these dainty-looking plants and have become believers, leading to a lot of angelonia used in Southern beds. When homeowners spotted them surviving in some of the toughest garden settings, they started seeking them out at retail and the market for angelonia took off. What was once considered the best garden plant you’ve never heard of is now a staple and one that garden communicators continue to recommend.

Historically a rangy and wild-growing perennial, coreopsis has certainly come a long way in the past few years, with new introductions being released showing more controlled habits and larger flowers, and even elegant bicolors. With hardiness as far south as Zone 9b, coreopsis is a fantastic, showy perennial that can be counted on to keep blooming no matter what conditions it encounters. Growers are even using the new, more controlled varieties in containers, adding to its versatility.

Definitely not new to southern growers, lantana has taken on a whole new identity with breeding that’s brought new colors, sizes and sterility to the class. Gold and orange tones are still the leading sellers, possibly due to recognition and trust in the performance, but bicolors and lighter tones are causing shoppers to take a second pass through the lantana bench when creating designer containers and landscapes.

Breeding for sterility has brought huge benefits to lantana, which now flowers consistently through the hottest months in the hottest climates. It took years of trials to prove this out, but was well worth it. An added benefit is that lantana is an excellent pollinator plant, and with so much attention on bees and butterflies (and habitat gardening, in general), it’s a must-have in a range of colors and habits.

Big blooms, a climbing habit and super heat performance make mandevilla a garden favorite. Being native to super-hot climates ensures performance in blazing summer sun and gardeners can’t seem to get enough mandevilla. Thankfully, breeders continue to work hard on this plant, bringing new varieties to market that fit into greenhouse production plans.

Leading marketers in our industry have done an admirable job shining the spotlight on mandevilla, causing it to be front and center in just about any garden retail setting, from the biggest big box stores to independent garden centers across North America. More mandevilla in the hands of home gardeners and landscapers means everyone gets a chance to see the performance and take note. When a climbing vine is needed for hot, summer performance, they all know where to look.

Beardtongue is a funny name … had to get that in before moving on to performance. Penstemon is probably an underrated perennial in most assortments. Yet, when it blooms, it grabs attention with beautiful lavender-purple flowers standing out tall above dark foliage, which looks great in the garden even after the flowers are gone. Dark foliage is popular and penstemon certainly fits the current trend.

There’s been recent breeding and introductions in this perennial class, refining a classic and adding grower-friendly attributes. No matter what season and covering most of North America in terms of hardiness, penstemon works great in heat-loving perennial mixes.

You can actually find some pentas up north these days, thanks to top-notch new breeding and increased attention, but it’s still primarily a southern-market rock STAR (pun completely intended.) Back in the day, pentas had a pretty wide range of bloom times and habits, and often went out of bloom when temps went way up. That’s no longer the case with new introductions focused on solving those challenges. Most of the newer pentas will continue to bloom all summer and continue to throw up more and more blooms all season, with a tidier habit.

The trend in succulents has brought increased attention on portulaca when savvy retailers move them from the long row of seed annuals into a more premium position or even add them to designer combos. It seems like the new generations of garden shoppers find them appealing and could bring new life to this old classic.

Breeding on portulaca is also ongoing, with grower improvements in crop timing and consumer improvements in flower size and color range. Also, make sure to include in your product comments for wholesale customers that portulaca is a great addition to pollinator and habitat gardens. Drought-tolerant, heat-tolerant, pollinator-friendly succulent plant … seems like a solid marketing message these days.

A summer-blooming perennial that beats the heat—these are attributes that make salvia ideal for this list. And like others already mentioned, new breeding is adding a lot of consumer attributes and interest to the class, thanks to bigger flowers, better habits and more colors from which to choose.

For growers, the latest genetics are also beneficial with first-year-flowering options and more compactness. Add to all of this the fact that many southern botanical gardens list salvia towards the top of their “best-performing summer perennials” lists and there’s no doubt the salvia market is poised for significant growth in the coming years.

It really doesn’t get much more low maintenance than sedum, but historically, sedum hasn’t been all that interesting. That’s certainly changed in the past few years, with new selections in brighter colors, and with weird and wild plant structures and habits. Shoppers love the chartreuse varieties, and when they realize sedums are perfect for the driest and hottest areas of the garden, they can’t get enough. That’s fine because there’s a huge range of succulents for you to choose from when building an assortment—from tall and bold to low-growing groundcovers and everything in between.

This one sort of goes without saying—we all know annual vinca is a hot-climate staple. But it’s also another class with constant breeding attention from companies around the globe. The result is better and better genetics, with increased diversity in habit, color range and improvements in disease resistance. Shoppers and landscapers in hot climates can choose from mounding and trailing varieties now, adding to the number of places vinca can be used. Some of the latest genetics add unique color variations to the mix and we’re starting to see vinca incorporated into designer combinations, as well.

The Chicago Botanic Garden called zinnias the “hardest-working flower in the summer garden” and they weren’t exaggerating. Their hot summer performance is exceptional and their tolerance to drought and propensity for continuous blooming makes them one of the best on this list. A wide range of vibrant colors, and single- and double-flowered varieties means there’s a zinnia for any garden, landscape or municipal-sized container. You most likely have zinnias in your assortment, but when you’re moving the portulaca to a more prominent position, grab some zinnias, as well.

Here’s a wildcard to finish up the list: in the 1930s, cosmos were all the rage, winning an All-America Selections award of merit and finding a place in just about every garden. And they were fantastic, blooming in the hottest conditions with very little effort on the part of the gardener. But since then, they’ve been somewhat forgotten, although there have been new intros as recently as a few years ago. While you can still find cosmos on availability lists from time to time, maybe it’s time to give them some more attention. They seem to fit current trends well, and with a whole new group of gardeners emerging, what’s old can certainly be new again if the message is right. GT

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