Summer’s Hottest Selections: Bring on the Heat — These Plants Are Ready!
Cultivar entries at the University of Florida Trial Garden are subjected to heat, humidity and regular afternoon thunderstorms. Average summer weather conditions are days in the mid-90s, nights in the low 70s and 6-7 inches of rainfall each month (Table 2). We plant the trial garden in late March from 80-mm Ellepots and evaluate each cultivar every two weeks from mid-April until early August. A complete list of all the cultivars in the trial and their performance for this year can be found on our website (trialgarden.ifas.ufl.edu).
Top summer performers are selected in two categories, flowering and nonflowering, based on excellent garden performance during June and July. This year, all cultivars chosen had a summer average of 4 or better on a 1-5 scale. A complete list of the top performers can be seen in Table 1. In this list, you will find many familiar crops and also some repeat winners from last year's trial. The focus of this article will be on some of the newer, underused crops as well as new or improved cultivars from established crops that gardeners can be successful with during the summer months.
Caladium 'Firecracker Red' (University of Florida breeding)
Caladiums are a great summer crop, especially for landscapers and home gardeners looking to add a splash of color in a shady location. 'Firecracker Red' is a new caladium introduction from the University of Florida and has red leaves edged with green margins. During the breeding process, they were selected under full sun conditions so they can tolerate high light environments. Our plants were grown under 30-percent shade in the garden and did not show any signs of sunburn. In lower light environments (in shady spots and in late afternoon) you can see a glossy sheen on the leaf surface. One caveat with all caladium varieties: They are slow to emerge and fill in during the early spring months, but they more than make up for it with their summer performance.
Colocasia 'Maui Magic' (Ball Seed)
'Maui Magic' comes from breeding work done in Hawaii and is well suited for tropical locations. It grows rapidly in warm temperatures and can be used as a summer tropical in the Northern and Midwestern states during the summer. The leaves are dark black-green and can reach 30-36 inches long and 18-24 inches across, and the plants can grow up to 6 ft. tall during the summer in a warm locale. 'Maui Magic' produces an abundance of leaves held on sturdy, upright petioles, creating the appearance of a dense, full plant. The foliage moves in the breeze and can provide a visual and textural focus to a garden or landscape area. One word of caution: This colocasia is not suited for small spaces and can overtake a mixed planter if the container is not large enough.
Cyperus 'King Tut' (Proven Winners)
Now here's an impressive plant in the landscape: In the trial garden, it managed to grow more than 5 ft. tall in just six weeks, and by the end of July, it was close to 7 ft. tall! It was planted in two locations in the garden, and we noticed that it did not grow quite as fast or as tall in the drier, sandier location. We would not recommend planting 'King Tut' in a mixed container unless the container is large enough to offset its height. This cultivar would work better as an accent plant in the landscape or in a large, decorative pot that can be positioned as a focal point on a deck or patio. In addition to 'King Tut,' Proven Winners has a smaller cyperus named 'Baby Tut' that will grow about 4 ft. tall in the landscape. Both 'King Tut' and 'Baby Tut' are available as Proven Selections items.
Duranta 'Gold Edge' (GroLink)
Duranta has long been grown as a shrub or small tree for its flowers and fruit. Recently, though, there has been an increase in the number of cultivars with variegated or solid gold leaves. 'Gold Edge' is a selection with bicolor green and gold leaves. It grew 3_-4 ft. tall by August but had excellent branching and a dense canopy. This cultivar did not flower during the trial season, but the lack of flowers doesn't diminish its attractiveness. It is a stunning addition to a garden based on foliage color alone and can be placed in the back of a landscape bed to add height and depth or planted as a focal point in a small garden. It could be used in a mixed container if its growth is kept in check.
Impatiens 'Fanfare Bright Coral' (Ball FloraPlant)
This year we provided participating companies the option of planting their impatiens in either full sun or 30-percent shade in our trials. We pitied the impatiens planted in full sun, thinking they weren't going to live very long. However, many of them ended up surprising us and held their own with many of the sun-tolerant crops. We trialed three Fanfare cultivars this year, and all had similar growth habits. 'Fanfare Bright Coral' had better flower coverage than 'Fanfare Fuschia Improved' and 'Fanfare Orchid' and flowered continuously throughout the summer. Plants reached 3 ft. tall in the garden and did not lodge except for when they were mildly water-stressed (they recovered nicely after rewatering, however, and did not show any adverse effects from wilting). In order to get peak garden performance from 'Fanfare Bright Coral' in the full sun, plants need to stay well-watered.
Musa 'Little Prince' (Agri-Starts I)
'Little Prince' is a dwarf, ornamental banana grown from tissue culture by Agri-Starts I. It grew 2_-3 ft. tall in five months from a rooted liner. Relative to other banana plants, the pseudostem is very thick in relation to its height. The leaves have a thick, leathery feel to them, and this helps them remain intact during thunderstorms. In addition, raindrops tend to bead up on the leaf surface, creating an attractive effect. For maximum effect in a landscape, 'Little Prince' should be planted far enough apart that they can be seen as individual plants. It will also perform admirably as a centerpiece in a mixed container or by itself in a decorative planter.
Pseuderanthemum 'Black Varnish' (GroLink)
'Black Varnish' is a maroon-leafed foliage plant that stands out in the garden with its glossy leaves and upright plant habit. Plants will produce an occasional inflorescence of pink flowers that appear to pop out from beneath the foliage. This cultivar is not designed to be used as a mass planting but as a color and texture accent, making it a natural for mixed containers or small home gardens. In can grow 4 ft. tall in a summer and is strong enough that it won't lodge in high winds.
Scaevola 'Surdiva White' (Suntory)
'Surdiva White' was named one of our "Outstanding New Varieties" this spring, and its strong performance continued through the summer as well. It is a compact scaevola cultivar with excellent potential for landscapes, hanging baskets and mixed containers. Two other colors are available — Blue and Light Blue — but White was the strongest garden performer for us. It maintained its compact growth habit, full plant appearance and good flower coverage from May through August. In production, it will not need a lot of growth regulators to keep its growth under control.
Sedum 'Lemon Coral' (Proven Winners)
We've had success growing sedum in Florida during the cooler months, but never during the summer months. Our heat and humidity have a tendency to make sedum stop growing: They don't die; they just sit and wait for the weather to cool off before they start growing again. However, this sedum has a comparatively vigorous growth habit. It continued to grow even as the regular afternoon thunderstorms started and the night temperatures stayed above 70¡ F. We did not see any disease or dieback problems occur. 'Lemon Coral' is a new introduction with attractive yellow to lime-green coloration. It is versatile in its use and could be planted in a succulent garden or a regularly watered annual bed.
Torenia 'Yellow Moon' (GroLink)
Torenia is another crop that is underused as a summer landscape plant. 'Yellow Moon' is a selection with light-yellow flowers with deep-purple throats. It was grown in full sun and did well once acclimated, but it would probably grow best in light shade. This cultivar has a trailing growth habit and can effectively be used as a groundcover or in a hanging basket. We pinched plants prior to transplant, and it helped them branch well and fill in the plot. 'Yellow Moon' will work well in home landscapes or as an accent planting in a commercial flower beds.