Cultivation Dahlia

1 cultivation

1.1 horticultural classification

1.1.1 history
1.1.2 modern system (rhs)
1.1.3 branding


1.2 double dahlias
1.3 stars of devil
1.4 award of garden merit (rhs)

cultivation

dahlias grow naturally in climates not experience frost (the tubers hardy usda zone 8), consequently not adapted withstand sub-zero temperatures. however, tuberous nature enables them survive periods of dormancy, , characteristic means gardeners in temperate climates frosts can grow dahlias successfully, provided tubers lifted ground , stored in cool yet frost-free conditions during winter. planting tubers quite deep (10 – 15 cm) provides protection. when in active growth, modern dahlia hybrids perform in well-watered yet free-draining soils, in situations receiving plenty of sunlight. taller cultivars require form of staking grow, , garden dahlias need deadheading regularly, once flowering commences.

horticultural classification
history

the inappropriate term d. variabilis used describe cultivars of dahlia since correct parentage remains obscure, involves dahlia coccinea. in 1846 caledonia horticultural society of edinburgh offered prize of 2,000 pounds first person succeeding in producing blue dahlia. has date not been accomplished. while dahlias produce anthocyanin, element necessary production of blue, achieve true blue color in plant, anthocyanin delphinidin needs 6 hydroxyl groups. date dahlias have developed five, closest breeders have come achieving blue specimen variations of mauve, purples , lilac hues.

by beginning of twentieth century number of different types recognised. these terms based on shape or colour, , national dahlia society included cactus, pompon, single, show , fancy in 1904 guide. many national societies developed own classification systems until 1962 when international horticultural congress agreed develop internationally recognised system @ brussels meeting year, , subsequently in maryland in 1966. culminated in 1969 publication of international register of dahlia names royal horticultural society became central registering authority.

this system depended on visibility of central disc, whether open centred or whether ray florets apparent centrally (double bloom). double bloom cultivars subdivided according way in folded along longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). if end of ray floret split, considered fimbriated. based on these characteristics, 9 groups defined plua tenth miscellaneous group cultivars not fitting above characteristics. fimbriated dahlias added in 2004, , 2 further groups (single , double orchid) in 2007. last group added, peony, first appeared in 2012.

in many cases bloom diameter used further label groups miniature through giant. practice abandoned in 2012.

modern system (rhs)

there more 57,000 registered cultivars, officially registered through royal horticultural society (rhs). official register international register of dahlia names 1969 (1995 reprint) updated annual supplements. original 1969 registry published 14,000 cultivars adding further 1700 1986 , in 2003 there 18,000. since hundred new cultivars added annually.

flower type

the official rhs classification lists fourteen groups, grouped flower type, abbreviations used rhs;

group 2 – anemone-flowered dahlias (anem) — centre of flower consists of dense elongated tubular florets, longer disc florets of single dahlias, while outer parts have 1 or more rings of flatter ray florets. disc absent.

(e.g. boogie woogie )












group 3 – collerette dahlias (col) — large flat florets forming single outer ring around central disc , may overlap smaller circle of florets closer centre, have appearance of collar.

(e.g. starsister , lilian alice , apple blossom )


















group 4 – waterlily dahlias (wl) — double blooms, broad sparse curved, curved or flat florets , shallow in depth compared other dahlias. depth less half diameter of bloom.

(e.g. cameo )


















group 5 – decorative dahlias (d) — double blooms, ray florets broad, flat, involute no more seventy 5 per cent of longitudinal axis, twisted , bluntly pointed. no visible central disc.

(e.g. berliner kleene )


















group 6 – ball dahlias (ba)— double blooms ball shaped or flattened. ray florets blunt or rounded @ tips, margins arranged spirally, involute @ least seventy 5 percent of length of florets. larger pompons.

(e.g. barbarry ball )












group 7 – pompon dahlias (pom) — double spherical miniature flowers made entirely florets curved inwards (involute) entire length (longitudinal axis), resembling pompon.

(e.g. small world )












group 8 – cactus dahlias (c) — double blooms, ray florets pointed, majority revolute (rolled) on more fifty percent of longitudinal axis, , straight or incurved. narrower semi cactus.

(e.g. nuit d eté )
























group 9 – semi cactus dahlias (s–c)— double blooms, pointed ray florets, revolute greater twenty 5 percent , less fifty percent of longitudinal axis. broad @ base , straight or incurved, spiky in appearance.

(e.g. mick s peppermint )












group 10 – miscellaneous dahlias (misc) — not described in other group.

(e.g. moonfire , carolina burgundy )


















group 11 – fimbriated dahlias (fim) — ray florets evenly split or notched 2 or more divisions, uniformly throughout bloom, creating fimbriated (fringed) effect. petals may flat, involute, revolute, straight, incurving or twisted.

(e.g. marlene joy )












group 12 – single orchid (star) dahlias (sino) — single outer ring of florets surround central disc. ray florets either involute or revolute.

(e.g. alloway candy )












group 13 – double orchid dahlias (dblo) — double blooms triangular centres. ray florets narrowly lanceolate , either involute or revolute. central disc absent.

(e.g. pink giraffe )












group 14 – peony-flowered dahlias (p) — large flowers 3 or 4 rows of rays flattened , expanded , arranged irregularly. rays surround golden disc similar of single dahlias.

(e.g. bishop of llandaff )













flower size

earlier versions of registry subdivided groups flower size. groups 4, 5, 8 , 9 divided 5 subgroups (a e) giant miniature, , group 6 2 subgroups, small , miniature. dahlias described group , subgroup, e.g. 5(d) ‘ace summer sunset’. dahlia societies have continued practice, neither official nor standardised. of 2013 rhs uses 2 size descriptors

dwarf bedder (dw.b.) — not exceeding 600 mm (24 in) in height, e.g. preston park (sin/dwb)
lilliput dahlias (lil) — not exceeding 300 mm (12 in) in height, single, semi-double or double florets 26 mm (1.0 in) in diameter. ( baby or top-mix dahlias), e.g. harvest tiny tot (misc/lil)

sizes can range tiny micro dahlias flowers less 50mm giants on 250mm in diameter. groupings listed here new zealand society.

giant flowered cultivars have blooms diameter of on 250mm.
large flowered cultivars have blooms diameter between 200mm-250mm.
medium flowered cultivars have blooms diameter between 155mm-200mm.
small flowered cultivars have blooms diameter between 115mm-155mm.
miniature flowered cultivars have blooms diameter between 50mm-115mm.
pompom flowered cultivars have blooms diameter less 50mm.

in addition official classification , terminology used various dahlia societies, individual horticulturalists use wide range of other descriptions, such incurved , abbreviations in catalogues, such co collarette.

branding

dahlinova carolina burgundy (misc)

some plant growers include brand name in cultivar name. fides (part of dümmen orange group) in netherlands developed series of cultivars named dahlinova series, example dahlinova carolina burgundy . these group 10 miscellaneous in rhs classification scheme.

double dahlias

in 1805, several new species reported red, purple, lilac, , pale yellow coloring, , first true double flower produced in belgium. 1 of more popular concepts of dahlia history, , basis many different interpretations , confusion, original discoveries single flowered types, which, through hybridization , selective breeding, produced double forms. many of species of dahlias then, , now, have single flowered blooms. coccinea, third dahlia bloom in europe, single. 2 of 3 drawings of dahlias dominguez, made in mexico between 1570–77, showed definite characteristics of doubling. in days of dahlia in europe, word double designated flowers more 1 row of petals. greatest effort directed developing improved types of double dahlias.

during years 1805 1810 several people claimed have produced double dahlia. in 1805 henry c. andrews made drawing of such plant in collection of lady holland, grown seedlings sent year madrid. other doubles of time did not resemble doubles of today. first modern double, or full double, appeared in belgium; m. donckelaar, director of botanic garden @ louvain, selected plants characteristic, , within few years secured 3 double forms. 1826 double varieties being grown exclusively, , there little interest in single forms. time so-called double dahlias had been purple, or tinged purple, , doubted if variety untinged color obtainable.

in 1843, scented single forms of dahlias first reported in neu verbass, austria. d. crocea, fragrant variety grown 1 of humboldt seeds, interbred single d. coccinea. new scented species not introduced until next century when d. coronata brought mexico germany in 1907.

the exact date dahlia introduced in united states uncertain. 1 of first dahlias in usa may d. coccinea speciosissima grown mr william leathe, of cambridgeport, near boston, around 1929. according edward sayers attracted admiration, , @ time considered elegant flower, eclipsed splendid scarlet, countess of liverpool . 9 cultivars listed in catalog thornburn, 1825. , earlier reference can found in catalogue linnaean botanical garden, new york, 1820, includes 1 scarlet, 1 purple, , 2 double orange dahlias sale.

sayers stated no person has done more introduction , advancement of culture of dahlia george c. thorburn, of new york, yearly flowers many thousand plants @ place @ hallet s cove, near harlaem. show there in flowering season rich treat lovers of floriculture : every variety can seen growing in 2 large blocks or masses lead road dwelling-house, , form complete field of dahlia foreground house. mr t. hogg, mr william read, , many other known florists, have contributed in vicinity of new york, introduction of dahlia. indeed general has become taste every garden has show of dahlia in season. in boston there many collections, collection messrs hovey of cambridgeport mentioned.

in 1835 thomas bridgeman, published list of 160 double dahlias in florist s guide. 60 of choicest supplied mr. g. c. thornburn of astoria, n.y. got of them contacts in uk. not few of them had taken prices @ english , american exhibitions .

stars of devil

in 1872 j.t. van der berg of utrecht in netherlands, received shipment of seeds , plants friend in mexico. entire shipment badly rotted , appeared ruined, van der berg examined , found small piece of root seemed alive. planted , tended it; grew plant identified dahlia. made cuttings plant during winter of 1872-1873. entirely different type of flower, rich, red color , high degree of doubling. in 1874 van der berg catalogued sale, calling dahlia juarezii honor mexican president benito pablo juarez, had died year before, , described ...equal beautiful color of red poppy. form outstanding , different in every respect of known dahlia flowers. .

this plant has perhaps had greater influence on popularity of modern dahlia other. called les etoiles du diable (stars of devil) in france , cactus dahlia elsewhere, edges of petals rolled backwards, rather forward, , new form revolutionized dahlia world. thought distinct mutation since no other plant resembled found in wild. today assumed d. juarezii had, @ 1 time, existed in mexico , subsequently disappeared. nurserymen in europe crossbred plant dahlias discovered earlier; results became progenitors of modern dahlia hybrids today.

award of garden merit (rhs)

as of 2015, 124 dahlia cultivars have gained royal horticultural society s award of garden merit, including:-