Gardenia 'Double Mint'
Gardenia Heaven Scent®
Gardenia Pinwheel®
Gardenia Pinwheel®

Why Gardenia jasminoides?

 

 

                                                                      Michael A. Dirr, PhD.

                                                                      Plant Introductions, Inc.

 

 

Answer is . . . why not? The proliferation of new and improved cultivars has heightened enthusiasm for this most recognizable and time-honored garden plant. Primarily a Chinese native, found in 15 provinces, also Taiwan, where it grows in thickets and forests at streamsides, on mountain slopes or hills, in valleys or fields, near sea level to 5000’. The species displays significant genetic and phenotypic variation; a fact undergirded by the tremendous range of cultivars. The Flora of China notes sizes from one to ten feet in height. I observed similar size variation on plants in cultivation.

 

Many references ascribe Zone 8 and warmer adaptability, but breeding opened the portal to increased hardiness (solid 7, perhaps 6b), more restrained habits and notable floral traits (single, double, persistent reblooming). Earlier introductions like ‘Kleim’s Hardy’ (single) and ‘Chuck Hayes’ (double) proved that a dollop of cold hardiness was present in the genome.

 

For my University of Georgia program the hardiness leap-forward came in ~1983 when I traded Illicium seed for wild-collected, cold-hardy Chinese Gardenia seed. Certainly, I had no idea these seeds would morph into the more cold hardy ‘Shooting Star’, ‘Griff’s Select’, Heaven Scent®, and Pinwheel® over a 30 year period.

 

In early April 2007, a field trial of seedlings from cold hardy taxa and known cultivars were severely inured or killed at the Horticulture Farm. Low temperatures were 28.6, 26.6, 33.6, and 31.6 on April 7, 8, 9, 10, respectively. Taxa like ‘Radicans’ were killed; ‘Frost Proof’ had 50% injury, while seedlings from Heaven Scent® and Shooting Star-01-03 (sister seedling of Heaven Scent®, but not introduced) displayed variable injury. Only numbers 2, 8, and 18 from Heaven Scent® were unscathed; not a single dead leaf. Subsequent testing (2009-2010) by Mike Hayman in Louisville, KY, with cold approaching zero, showed number 18 with a few tip burned leaves; number 8 with all dead leaves, and number 2 about 50% leaf kill. Number 18 became Pinwheel® (‘PIICA-1’, PP22,510) and was licensed to McCorkle Nurseries, Inc. by PII.

 

All the seedlings were singles, with abundant flowers in May-June, variable rebloom into September, with number 18 the most prolific. Single-flowered gardenias are not as highly prized as doubles. To be sure, there are many doubles on the market, so some breeder/selector figured it out. How does PII move beyond singles?

 

I discovered two fruits on ‘Chuck Hayes’, a cold-hardy to ~5°F, double flowered, typically sterile cultivar that originated in Virginia Beach, VA (HortScience 29:829-830, 1994). Dr. Raulston promoted this and plants had reached 5 to 6’ high and wide in the Arboretum. Seeds were cleaned, sown, with several resultant doubles, two of which became ‘Double Delight’ and Double Mint™, the latter with lustrous, leathery dark green foliage, more compact habit, 2” diameter, elegant, double flowers and persistent rebloom. Absolute hardiness is unknown, but based on no injury at 6°F on January 7, 2014, a strong 7a is justified. The serendipitous double-flowered seedlings from open-pollinated ‘Chuck Hayes’, as well as another read of the HortScience paper, portend a pathway to more doubles via cross-pollination.

 

Heaven Scent® and Pinwheel® (singles) were crossed with Double Mint™ (double) in 2011. In 2013, eight double-flowered seedlings were selected, one with perfectly formed, 3” diameter, glistening white, fragrant flowers. The range of leaf shapes (rounded, ovate, linear) and habits (compact, rigidly upright, spreading) was remarkable. The majority of the seedlings and all the early double selections were not injured by the January 7th 6°F.

 

The logical question to pose . . . where can breeders probe for Gardenia improvement? A true Zone 6 cultivar with double flowers and potent rebloom would prove a game-changer. I have yet to witness a trace of pink in seedling populations. Somewhere in the Gardenia jasminoides genome, a pink gene is waiting to be expressed!? I am hopeful.

 

The following checklist provides a guide to nomenclature and characteristics. Those described in the Dirr Manual (2009) or Encyclopedia (2011) are designated with a (D). On occasion, a notation has been added.

 

Checklist

 

‘Aimee Yoshida’ (‘Aimee’, First Love™) (D)

 

‘August Beauty’ (D)

 

‘Belmont’ (‘Hadley’ PP93) (D)

 

‘Billie Holiday’ (D)

 

Bitty Boutonniere™ (‘Leethree’ PPAF) – Mini, single white flowers, reblooming, compact, rounded, mounding, 2.5’ by 3.5’, Zone 7 to 10, HGTV introduction in 2014.

 

‘Buttons’ (PPAF) – Semi-double, 1.5-2’ by 1.5-2’ (2.5’ by 2.5’), Zone 8-10, Ball Ornamentals.

 

‘Candle Light’ (D)

 

‘Chuck Hayes’ (D)

 

Coconut Magic™ (PPAF) – Extra large cream-white flowers, listed as 5-6” diameter, 3-4’ by 3-4’, Zone 8b-11, Ball Ornamentals.

 

‘Crown Jewel’ (PP18,896) (D)

 

‘Cutie Pie’ (D)

 

‘Daisy’ (D)

 

‘Daruma’ (D)

 

Double Decadence™ (‘Leefour’ PPAF) – Double white flowers, reblooming, upright habit, 3.5-4’ high and wide, Zone 7 to 10, HGTV introduction in 2014.

 

‘Double Delight’ – Double white, seedling of ‘Chuck Hayes’, not as cold hardy as ‘Double Mint’, 3’ by 3’.

 

‘Double Mint’ (PP23,507) – Double, perfectly formed, 2” diameter flowers, reblooming, lustrous dark green foliage, compact habit, 2.5-3’ by 2.5-3’, Zone 7 to 9, no damage at 6°F on January 7, 2014, bred by Plant Introductions, Inc., introduced by Bailey Nursery in First Editions®.

 

‘Fortuneiana’ (D)

 

‘Fragrant Pathways’ (D)

 

‘Frostproof’ (D)

 

‘Four Season’s’ (‘Kimura Shikazaki’) (D) – Excellent reblooming double

 

‘Fukurinkoba’ (D)

 

‘Glacier’ (D)

 

Golden Doubloom™ (‘sPg-3-015’) – Double white flowers, to 5” diameter, golden young leaves, mature green, best in light shade, listed as Zone 7 which I doubt; leaves are large which usually equates with less hardiness, Garden Debut®.

 

Golden Magic (D) – 2 to 3” diameter double yellow flowers, 2-3’ by 2-3’, Zones 8b-11, Ball Ornamentals

 

‘Grif’s Select’ (D)

 

Heaven Scent™ (‘Madga 1’ PP19,988) (D)

 

‘Ice Diamonds’ – Single with camellia-like petals, foliage looks like ‘Frost Proof’, 3-4’ by 3-4’, described in The Garden 137(12):40-41, 2012.

 

Jenkins Form (D)

 

Jubilation™ (‘Leeone’ PP21,983) (D) – Double-flowered, reblooming, 3-4’ by 3-4’, bred by Robert E. Lee from open-pollinated ‘Daisy’, part of Southern Living Plant Collection, heavy cold damage at 6°F on January 7, 2014, at Plant Introductions.

 

Jumbo Lemon Drop™ (same as ‘Golden Magic’) – HGTV Collection rename

 

‘Kimberly’ (PP15,189) (D)

 

‘Kleim’s Hardy’ (D)

 

‘Lasting Beauty’ – White, double, good rebloomer, quite cold tolerant

 

‘Lynn Lowrey’ (D)

 

‘Linwood Hardy Gardenia’ – White, single, 3-4’ by 2-3’, Zone 7, Greenleaf Nursery

 

‘Martha Turnbull’ – Single flower, abundant fruits, from St. Francisville, LA

 

‘Miami Supreme’ (D)

 

‘Michael’ (D)

 

Moonspinner™ (‘Vietnam Star’ PPAF) – Single, 3-3.5’ by 3-3.5’, Zones 9-11

 

‘Mystery’ (D)

 

Pinwheel® (‘PIIGA1’ PP22,510) – Single white flowers, reblooming, 2 to 2.5” wide, larger than those of Heaven Scent®  compact habit, 3-4’ by 3-4’, lustrous dark green leaves, no foliar injury at 6.6°F in Dirr garden on January 7-8, 2014, also survived near zero temperatures in Louisville, KY; open-pollinated seedling of Heaven Scent®.

 

‘Radicans’ (‘Prostrata’) (D)

 

‘Radicans Variegata’ (D)

 

‘Rosedown Beauty’

 

‘Rosedown Star’ – Large lustrous dark green leaves and single star-like white flowers followed by orange fruits, Jane Symmes introduction from historic Rosedown Plantation, St. Francisville, LA, large plant 8-10’ by 6-8’, Zone 7 to 9, offered by Woodlanders, Aiken, SC.

 

Scented Pearls™ (same as ‘Buttons’; in HGTV collection)

 

Scentsation™ - Single, 3.5’ by 4’, Zones 7 to 10.

 

‘Shooting Star’ (D)

 

‘Star Bright’ (PP8,887) (D)

 

‘Star Dust’ (PP21,541) – Single, resistant to Race 2, root rot nematode.

 

Starlite™ - Single, 3-4’ by 2-3’, Zones 8b-11, Ball Ornamentals

 

Summer Snow® (‘BAB1183’ PP22,791) – Double, waxy white, fragrant flowers, 4-5’ by 4-5’, hardy to 0°F, from Doug Torn, Buds and Blooms, Brown Summit, NC; listed in promotion as Zone 6 to 10 adaptable.

 

‘Variegata’ (D)

 

‘Veitchii’ (D)

 

‘Veitchii Improved’ (D)

 

‘Veitchii Variegated’ (D)

 

‘Vietnam’ – Large leaf, single, absolutely fried in April 2007 freeze.

 

‘W.B. Cole’ (D)

 

‘White Gem’ (D)

 

‘Yellow’ – White double flowers, quickly turn yellow, 6-8’ by 4-6’, Zones 8 to 10, offered by Woodlander, Aiken, SC.