What Are the Hardiest Gardenia Varieties?

Since January is the month Alexander Garden was born, let’s take a timely look at the popular shrub that commemorates him.

note: Often the purpose of links is to indicate further information is available on related topics. The links here are independent, which means this web site has nothing to do with them!

a photograph of a gardenia plant growing in the snow in January

The Frost of Death was on the Pane—
“Secure your Flower,” said he.
Like Sailors fighting with a Leak
We fought Mortality—

In the past few years, many people who have grown gardenias outdoors have shared Emily Dickinson’s lament for the unspecified vegetable victim from poem F 1130. You may wonder just what the hardiest gardenia varieties are. The answer is developing, so let’s consider what we know about what’s available.

 

an illustration of a branch and single flower of Gardenia from the 1820s by Kawahara Keiga; the Japanese name for the plant is kuchinashi
Gardenia, or kuchinashi (1820s)
by Kawahara Keiga

Gardenia jasminoides, an evergreen shrub in the madder family, Rubiaceae, is an Asian plant that grows wild primarily in the subtropics, from India east to Vietnam, and north to Korea and Japan. In China it has been cultivated for around 1,000 years; single and double-flowered forms have long been known. Called zhi zi, it is first mentioned in the The Divine Farmer’s Materia Medica (Shennong Ben Cao Jing, 200–250 C. E.), the oldest Chinese herbal text, where it is placed in the second of three classes of herbs for its berries. Described as “human,” “commoner,” or “middle herbs,” the 120 plants in this group are considered therapeutic, but can have toxic or potentially toxic properties. In this category, we also find dianthus, peony, ginger, and cucumber.

Gardenia by Chinese artist Shen Zhou (1427–1509), from the album "Dreaming of Traveling While in Bed"
Gardenia by Shen Zhou (1427–1509) from the album “Dreaming of Traveling While in Bed”

The first plants to leave Asia and survive the long voyage were a single-flowered form brought to England in 1744 via the Cape of Good Hope on the Godolphian, a vessel of the British East India Company. The earliest published name was not the one we currently know, but Warneria augusta in 1755 because the plant was introduced to Europe by Richard Warner. The official name would be settled in a few years; for the full story, see “Naming the Gardenia” by Margaret Denny (1948).

The genus Gardenia and the species Fothergilla gardenii are named for the Scottish physician, botanist, and zoologist Alexander Garden (1730–91), who lived for many years in Charleston, South Carolina and corresponded with John Bartram, Benjamin Franklin, and Carl von Linné, among others. The naming was done by British linen merchant and naturalist John Ellis in 1760; the official name was published, however, in 1761. This is the reason both dates appear sometimes and both are correct in a way. Alexander Garden first grew it himself in 1762. He received two plants from England. One arrived dead and the other one died the next year.

One of the earliest illustrations of a gardenia made outside Asia. "The Jasmine? with a single flower per branch, double, coriaceous petals, that flowered in the curious garden of R. Warner, Esq. at Woodford, Essex, July 1758" by Georg Ehret (1708–70), plate 15 from Rare Plants and Butterflies (1759). Only two copies are recorded in American institutions: the Arnold Arboretum at Harvard University and the Library of the United States Department of Agriculture in Washington, D. C.
One of the earliest illustrations of a gardenia made outside Asia. “The Jasmine? with a single flower per branch, double, coriaceous petals, that flowered in the curious garden of R. Warner, Esq. at Woodford, Essex, July 1758” by Georg Ehret (1708–70), plate 15 from Rare Plants and Butterflies (1759). Only two copies are recorded in American institutions: the Arnold Arboretum at Harvard University and the Library of the United States Department of Agriculture in Washington, D. C.

The development of hardy gardenia cultivars began after the late 1970s and early 1980s brought severe winters to much of the eastern United States and killed many plants. At about the same time two nurserymen were working separately about 2,850 miles apart in Virginia and California; there was also a third in Georgia. Patenting did slow the introduction process, but second and third-generation hybrids are now on the market.

Given this trilemma in space and time, where to begin?

black-and-white illustration by John Tenniel of the King for Alice in WonderlandOh, yes: “Begin at the beginning, and go on till you come to the end; then stop.”

Gardenia jasminoides ‘Chuck Hayes’ (Plant Patent #8,755) was developed in the mid-1980s by Charles Hayes and Daniel Milbocker working at Virginia Beach. In June of 1983, Charles Hayes of Cavalier Nursery crossed an unnamed single variety with an unnamed double and selected the best of 400 seedlings after field testing and lab testing. It had very abundant double flowers. By the time this superior form was patented and formally introduced in 1993, Hayes had died and Daniel Milbocker at the Hampton Roads Agricultural Research and Extension Center in Virginia Beach handled the introduction.
The patent application describes ‘Chuck Hayes’ as having “cold tolerance similar to, if not superior to” ‘Kleim’s Hardy’ as well as superior heat tolerance. I suspect there’s a difference in how these two perform on the West Coast and in eastern states. ‘Chuck Hayes’ is known for producing a second flush of bloom on new growth, and the leaves are a bit larger than most hardy varieties. A tendency to turn yellow in winter has been noticed and improved upon, as you’ll see below. ‘Chuck Hayes’ has a semi-dwarf, spreading growth habit; the mature size is usually given as 3-4 feet in height by 4-5 feet wide, but a source in Maryland reports eventually to 6 by 7 feet with leaves up to 7 by 3 inches. It will survive temperatures a little below zero if grown in a location sheltered from wind and mulched for the winter, preferably with pine needles, oak leaves, or another material not likely to compact.

Gardenia 'Kleim's Hardy' in flowerKleim’s Hardy‘ (not patented, single) was discovered and introduced by Donald Kleim of the Henderson Experimental Garden in Clovis, California near Fresno in the San Joaquin Valley. In case you didn’t notice, William Henderson named his research plot after Luther Burbank’s Gold Ridge Experiment Farm, where he had trained. Kleim joined the Henderson operation in 1946 and took over in 1976 after the owner and founder William Henderson died. The record low in Fresno is 17° F set on January 6, 1913, followed by 18° in 1990, so although this temperature range in the upper teens is relatively cold for central California, it’s not growing conditions that you would expect to help select one of the hardiest Gardenia varieties. Kleim made his selection and first distributed plants in the late 1980s. The Gossler Farms Nursery in Springfield, Oregon received some of these early starts and would report that plants “thrived” after the temperature dropped to 0° F the winter of 1991. Even in Oregon they recommended a site with afternoon shade, not full sun. In the early 1990s, ‘Kleim’s Hardy’ was new but in commerce. The wholesale grower Monrovia would add it to their catalog in 1999, no doubt after a few years of trial and building up stock.

Dr. Michael Dirr would offer additional perspective on ‘Kleim’s Hardy’ after growing seeds collected by the Beijing Botanical Garden from the coldest part of the wild range. In short, he was not impressed, but admired its “lustrous black-green leaves.” A source in Virginia notes it has been evergreen down to -3° F. This variety definitely has a low, mounded habit, and reaches 2 to 3 feet tall and wide. Some authorities have wondered whether there is much difference between ‘Kleim’s Hardy’ and ‘Daisy’, ‘Daruma’, or at least the plants sold under those names in commerce. A side-by-side comparison of all the singles would seem worthwhile. The flowers on this one are usually around 2 inches across and numerous, that is, they compensate for their size with abundance. Although you only get one flush, the cute factor of a single Gardenia is undeniable.

a close view of flowers of Gardenia 'Kleim's Hardy'Dr. Michael Dirr would report that

For my University of Georgia program, the hardiness leap forward came around 1983 when I traded Illicium seed for wild-collected, cold-hardy Chinese gardenia seed. Certainly, I had no idea these seeds would produce the more cold-hardy ‘Shooting Star,’ ‘Grif’s Select,’ ‘Heaven Scent,’ and ‘Pinwheel’ over a 34-year period.

His first observation was that some of the Chinese seedlings had flowers bigger than ‘Kleim’s Hardy’ and some tolerated cold better. Dirr distributed seedlings to many people and horticulturist Mark Griffith propagated one he named ‘Grif’s Select.’ Parts of Dirr’s network would coalesce to become the gardenia research group at Plant Introductions, Inc. consisting of Rhonda Helvick, Oren McBee, Mark Griffith, Jeff Beasley, and Dirr.

Since the Chinese seeds Dirr grew would lead to several introductions, we’ll take the rest of the hardy gardenia varieties alphabetically from here.

‘Crown Jewel’® (Plant Patent #19896) is the best selection from a controlled cross between ‘Kleim’s Hardy’ (for dwarf habit, heavy bloom set) and ‘Chuck Hayes’ (for cold-hardiness, twice-blooming, and double flowers) made in 1998 by Philip Dark of Oakmont Nursery in Chatham County, North Carolina. Dark is a member of the consortium of growers, breeders, retailers and marketers that make up Garden Debut®, and he reports that cold testing is ongoing in Zone 5, which ought to be interesting (note my skepticism).
‘Crown Jewel’® is a spreading to prostrate gardenia that grows about 6 inches a year to 2 or 2 ½ feet in height and a spread of 4 to 6 feet. The intensely fragrant, 2- to 3-inch double flowers begin in early summer and repeat until frost, with a heavy flush in May or early June and another in September. Since ‘Crown Jewel’® blooms on both old and new wood, late frosts will not eliminate the fragrant floral display that year.

Plants of Gardenia 'Double Mint' in a nursery setting.
Plants of Gardenia ‘Double Mint’ in a nursery setting.

‘Double Mint’ (Plant Patent #23,507) is an open-pollinated seedling of ‘Chuck Hayes’ raised by Plant Introductions Inc. and introduced by Bailey Nurseries in the First Editions® branded plant line. Like ‘Crown Jewel’®, it has double, 2- to 3-inch flowers with great form and it reblooms. It also seems a little more resistant to root rot than other varieties. Reaching 2½-3 feet by 2½-3 feet, ‘Double Mint’ has a compact habit, and overall it makes a very beautiful small shrub. Plants are known to have survived 6° F with no damage, which suggests it could be top-hardy below zero. The growth habit is denser than ‘Chuck Hayes’, the leaves are smaller and narrower, and ‘Double Mint’ has foliage that tends to maintain its dark green color during winter better than ‘Chuck Hayes’, which often turns yellow-green in the cold. I would add that ‘Chuck Hayes’ seems to be a darker green overall and, at least as a young plant, this variety tends to be broader than tall.

Grif’s Select was introduced by Mark Griffith of Griffith Propagation Nursery and raised from Chinese seed distributed by Michael Dirr. The flowers develop into an abundance of red berries like its sibling varieties. ‘Grif’s Select’ is a cultivar that typically grows to 3 to 4′ tall and wide. It is particularly noted for its compact form, small leaves, fragrant single, daisy-like summer flowers to 3″ diameter, showy red berries (often called “seed capsules” or “hips”), and excellent winter hardiness. It was added to and dropped from the Proven Winners line, and now even Mark’s own operation isn’t growing it. A few years ago, Scott_6B tried 7 of the hardiest varieties and would report: “So far ‘Grif’s Select’ and ‘Summer Snow’ have clearly done better than the other varieties. I would probably give a very slight edge to ‘Summer Snow’ . . . ”

a gardenia with snow on the leaves
How much can a chilly plant survive? Here’s an unidentified Gardenia in a winter landscape.

‘Heaven Scent’® (Plant Patent #19,988) is another University of Georgia selection with hardiness similar to ‘Grif’s Select’ and ‘Shooting Star’, but more than most other varieties. With ‘Pinwheel’, it’s one of two cultivars licensed to McCorkle Nurseries for its Gardener’s Confidence Collection®, and they list ‘Heaven Scent’® as hardy to zone 6b. The flowers are single, and like its brethren they develop into an abundance of vividly colored berries. The petals are broader than ‘Pinwheel’ and they give a rounded bloom. Overall this cultivar is more compact than ‘Pinwheel’, distinguished by smaller leaves and more fruits.

Dirr mentions a variety ‘Lasting Beauty’ that doesn’t appear to be in commerce: double flowers, good re-bloomer; quite cold-tolerant. If anybody knows more, please put it in a comment below. Could this name be a confusion with ‘August Beauty’ or a corruption of it?

‘Pinwheel’ (Plant Patent #22,510) has single white flowers, larger than those of ‘Heaven Scent’ and reblooms. They have narrow petals, giving flowers a graceful, open effect, and tend to be about 2½ inches wide. The growth habit is compact, reaching 3-4 by 3-4 feet; lustrous dark green leaves. Dirr reports leaf injury after 6.6° F on January 7-8, 2014, and that ‘Pinwheel’ also survived temperatures near zero in Louisville, Kentucky. It originated as an open-pollinated seedling of ‘Heaven Scent’ and has been licensed to McCorkle Nurseries by Plant Introductions, Inc. for its Gardener’s Confidence® collection. They give ‘Pinwheel’ a 5-degree hardiness edge, listing it for zones 6a to 9.

‘ScentAmazing’ (Plant Patent #27,601) was bred by Robert Edward (Buddy) Lee and new in 2015-16 as an addition to the Southern Living Plant Collection. It was identified during October of 2000 in a group of openly pollinated seedling plants of unpatented Gardenia ‘Daisy’ grown in Independence, Louisiana. Buddy Lee finds it similar in most horticultural characteristics to the seed parent variety, but better. Plants of the new cultivar produce flowers that are smaller and stronger, grow with a habit that is overall more compact, and foliage is darker green and shinier. The flowers are small, single, fragrant, and rebloom is excellent. Size is estimated to reach 2½-3 feet by 2½-3 feet, which seems to be “the magic number” nowadays, and ‘ScentAmazing’ is listed as hardy to 0° F.

One more frozen Gardenia--no particular variety--in an outdoor setting.
One more frozen Gardenia–no particular variety–in an outdoor setting.

‘Shooting Star’ (not patented) is a compact cultivar that typically grows 3 to 4 feet tall (MOBOT) or an upright grower to 6–8 feet tall and wide (Steve Bender), with large leaves and single flowers in late spring and early summer. Although this cultivar doesn’t rebloom, Dirr noted its extended period of display and “exceedingly fragrant flowers.” He also says ‘Shooting Star’ did not discolor or die back from winter over 18 years of observation in Athens, Georgia, and in laboratory hardiness tests the stems survived −11° F, making this cultivar safely hardy at least to 0° F. It derives from seeds sent to the University of Georgia from the Beijing Botanical Garden that were reportedly collected from the coldest part of its natural range.

‘Summer Snow’ (Plant Patent #22,797) comes from Doug Torn of Buds and Blooms Nursery in Brown Summit, North Carolina. It has double, waxy white, fragrant flowers up to 4½ inches across and beautiful glossy leaves. A moderate grower to 4-5 feet by 4-5 feet; listed in promotion as hardy to 0°F and adaptable to Zone 6. Around 1993, Torn received cuttings from what he believes to be a hybrid plant of unknown parentage in Dania Beach, Florida. Over the next 14 seasons, he grew them in USDA Zone 7 (Guilford County, North Carolina) and selected the best plants for sturdiness. Then his top candidates were tried for two years in USDA Zone 6, and he narrowed them down to this one, ‘BAB1183’.

‘Sweet Star’ (‘PIIGA-III’, Patent Pending) was selected from the same cold-hardy Chinese seed that spawned other University of Georgia varieties. It has shown no injury after many years of evaluations at Plant Introductions, Inc. in Watkinsville, Georgia. Desirable features include its compact, rounded habit, extremely lustrous, leathery dark green foliage, and semi-dwarf size, reaching 3-5 by 4-5 feet. The single flowers are abundant enough to hide the leaves at peak bloom, and it’s a potent rebloomer. Listed as Zone 7-10, ‘Sweet Star’ is offered by Bailey Nurseries in the First Editions® brand (2017).

‘Sweet Tea’ (Plant Patent #27,258) resulted from a controlled cross between ‘Double Mint’ and ‘Pinwheel’. It has a habit more upright than ‘Double Mint’, reaching 3-5 feet by 3-5 feet. The sweetly-scented double flowers reach 4 inches in size, and lustrous dark green foliage sets them off well.
This introduction has proven hardier than nearly all other doubles. During the winter of 2013-14, plants in containers survived 4 to 6 °F, which shows great promise. ‘Sweet Tea’ appears to be sterile, which means no colorful berries.

That makes a dozen potentially worthy of a try. What can you add from your experiences? Leave additional observations below.

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3 thoughts on “What Are the Hardiest Gardenia Varieties?

  • January 21, 2018 at 10:03 am
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    Todd,

    Thank you for this excellent piece on hardy Gardenias! I’ve often wondered on the heritage of the newly introduced Gardenias and their relation to Kleim’s hardy because of their similarity. It’s still a mystery to me on why Don Kleim would introduce a hardy Gardenia in fairly warm Central California, but he was a well known plant smith in the trade. Your writing is well researched and interesting to me. I’ll share it with my staff and my customers.

    Reply
  • January 28, 2018 at 7:07 pm
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    well done and accurate. pretty amazing what happened to develop cold hardy gardenias over the past few years. I like sweet tea. have in ground and container in personal garden. no discoloration this year. tennis ball-size, double flowers of great substance. this might be the best double out there. developed by plant introductions and licensed to bailey. I have no financial ties to plant as our company was sold to bailey in 2015. over the years have tested many/most gardenias. impressed with this one. three years ago, fruits developed on sweet tea and 100s of seedlings were germinated. had to pitch them for business reasons but to this day, I wonder what might have resulted, especially since the fruits were the result of self-pollination.. many people will tell you that double flowers are sterile. plants don’t read the literature and often surprise. keep up the good work. Mark Griffith forwarded your piece to me. thanks

    Reply
    • January 29, 2018 at 10:55 pm
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      I laughed out loud when you said plants don’t read the literature. Here’s an echo from French physiologist Claude Bernard: “It is that which we do know that is the great hindrance to our learning, not that which we do not know.” Glad to hear your enthusiasm for ‘Sweet Tea’ in particular; your endorsements always wield considerable heft.

      Reply

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