|Standard Cyclopedia of Horticulture|
Dahlia (named after Professor Andreas Dahl, a Swedish pupil of Linnaeus, and author of "Observationes Botanicae"). Syn. Georgina. Compositae. Stout perennial herbs, sometimes somewhat woody, much grown out-of-doors for the rich and profuse autumn bloom. Plate XXXIV.
Tuberous-rooted (Fig. 1205): st. mostly erect, branching, glabrous or scabrous: Lvs. opposite, 1-3-pinnate: heads long-peduncled, large, with yellow disk and rays in a single series and mostly in shades of red and purple and also in white (in cult.); ray-fls. neutral or pistillate, disk-fls. perfect and fertile; involucre double, the inner series of thin scales that are slightly united at base, the exterior series smaller and somewhat leafy; receptacle plane, bearing chaffy scales; rays spreading, entire or minutely 3-5-dentate: fr. oblong or obovate, strongly compressed on the back, rounded at the apex, obscurely 2-toothed or entirely bald.—Probably 10 or 12 species, in the higher parts of Mex., some of them now much modified by cult., and the domesticated forms often difficult of systematic study. The nomenclature of the group is confused because systematists are not agreed on the rank to be given to forms that have received independent names. Voss (Bluinengartnerei) combines the three species of Cavanilles, D. pinnata, D. coccinea, and D. rosea, all under the name D. pinnata. His arrangement is as follows: D. pinnata, Cav.; var. coccinea, Voss (D. coccinea, Cav. D. rosea, Cav., in part. D. frustranea, DC. D. crocea, Poir. D. bidentifolia and D. mexicana, Hort.); var. gracilis, Voss (D. gracilis, Ort.); var. Cervantesii, Voss (D. Cervantesii, Lag.); var. variabilis, Voss (D. variabilis, Desf. D. rosea, Cav., in part. D. sambueifolia, Salisb. D. superflua, Ait. D. purpurea, Poir.). It seems to be well, however, to keep D. rosea and D. coccinea distinct, and perhaps also D. pinnata; and this is the method adopted for the present treatment. Of the three Cavanillesian names, D. pinnata has priority.
D. gracilis, Ort. Lvs. bipinnate and ternately divided, glabrous, the lfts. small, ovate and coarsely toothed: fls. brilliant orange-scarlet; outer bracts of involucre almost orbicular: 4-5 ft, making a dense bush with very slender growths, bearing heads 2½-3in. across. Apparently not in general cult.—D. pinnata, Cav. Plant scarcely 3 ft, high, glabrous: Lvs. 5-foliolate; lfts. ovate, crenate-dentate, glaucous beneath, sessile; rachis winged: fls. large, solitary; female corolla large, blue-red, exterior involucre with 6-7 bracts, ovate, narrowed toward the base, spreading and reflexed incurved, the interior with coriaceous lobes. The plate of Cavanilles shows semi-double fls., i.e. with several rows of rays, with the rays incurved at the margin and becoming at the base nearly tubular.—It. Zimapanii, Roezl, is by some retained in Dahlia and by others referred to Bidens; in this work it is described under Cosmos (C. diversifolius). Wilhelm miller. L. H. B.
Types and varieties of the dahlia.
Practically all of the named varieties of dahlias have come from one immensely variable species, usually known as D. variabilis, but more properly as D. rosea. For garden purposes, however, a second form of great importance, D. Juarezii, the parent of the Cactus forms, must be kept distinct. There are other species cultivated to a slight extent. It is curious that these showy plants should be closely related to a common weed, the beggar's tick, of the genus Bidens; but other species of Dahlia have leaves whose forms pass gradually into those of Bidens. Other close allies are Cosmos and Coreopsis. Cosmos flowers are some shade of purple, rarely white in wild nature, and only one species has yellow flowers; Coreopsis has yellow flowers only; Bidens, yellow or white; and none of these genera has produced double-flowered forms of the first importance. Dahlia has all these colors and more, being far richer in bright reds, and lacking only sky- blue and its closely related hues, which are seen to perfection in the China asters.
Although dahlias are popular plants, especially in old gardens, they are destined to still greater popularity from the new "Cactus," "Decorative," "Peony-flowered," and "Collarette" types. There exists a prejudice against dahlias in many localities in which these new types have never been seen. This prejudice is part of a reaction against formal and artificial flowers in general. The old-time dahlias were round hard and stiff like a ball. The new-time dahlias are flatter, and tend toward loose, free, fluffy chrysanthemum-like forms. The dahlia has now become immensely variable.
Of the important and very variable florists' flowers, the dahlia was one of the latest to come into cultivation. The first break of considerable importance in the wild type occurred about 1814. Up to that time there were perhaps a dozen well-marked colors in good single-flowered varieties. Dahlias had been cultivated in Europe since 1789, and it is a curious fact that they showed signs of doubling the very first year of their European residence; but it was not until twenty- five years later that a marked gain in doubling was made. The dahlia seemed to be undeveloped until 1814, when the era of doubling began. Before another twenty-five years had passed, the dahlia had sprung into the front ranks of garden plants. In 1826 there were already sixty varieties cultivated by the Royal Horticultural Society. In 1841, one English dealer had over 1,200 varieties. Today it is not uncommon for the leading tradesmen to keep 500 to 1,000 distinct varieties. In the absence of good records, it is conjectured that over 3,000 different names of varieties have been published in the catalogues. Most of the varieties are the Show and Fancy types, which are as spherical and regular as possible, and differ only in color. At first the distinction between the two types seems to have been the same as that between "self- colored" and "variegated" flowers in general. Lately, for purposes of exhibition in prize competitions, the following arbitrary distinction has been adopted: A Show dahlia (Fig. 1210) is often of one color; but if the edges of the rays are darker than the ground-color, the variety may be exhibited in the Show section. A Fancy dahlia (Fig. 1211) always has two or more colors, and if the rays are striped or if the edges are lighter than the ground-color, the variety must be exhibited in the Fancy section. The two types reached full perfection certainly by 1840, and after that date the improvements were mostly in matters of secondary importance. Most of the longest-lived varieties belong to the Show and Fancy type. These types held full popularity until about 1879, when the first Cactus dahlia appeared in England with a promise of new and freer forms. This form is the one which is perhaps farthest removed from nature, and it is probably so highly esteemed largely because the most work has been spent on it.
A reaction against formalism in all departments of life arid thought set in about the time of the American Civil War. It was in the sixties that the Japanese chrysanthemums did much to emancipate the floral world. With dahlias the reaction came much later and has proceeded more slowly. The first Cactus dahlia was so called because of its resemblance in form, but chiefly in color, to the brilliant crimson-flowered Cereus speciosiasimus, a well-known garden plant (which is known in the present work as Heliocerus speciosus). The name is now highly inappropriate because the color range of the pure Cactus type has been extended to include all of the important well-defined colors of which the dahlia seems capable. The original Cactus dahlia was named Dahlia Juarezii, after President Juarez, the "Washington of Mexico." It was pictured for the first time in the Gardeners' Chronicle for 1879, and this interesting picture is here reproduced in a reduced size in Fig. 1207. The type is still cultivated under the same name and in all essentials seems to be unchanged. Forms of the Cactus dahlia are shown in Figs. 1212, 1213.
The origin of the Cactus type, as of all the other types of dahlias, is uncertain, and our efforts to secure full and definite information upon some of the most interesting points may perhaps always be baffled.
A Dutch dealer secured a root from Mexico that produced one plant which is the parent of all the Cactus forms. It is not known whether the seed which may have produced the original root came from a wild or a cultivated flower. It has been said that seedlings of D. Juarezii have produced in cultivation forms approaching the Show type of D. rosea. The reverse process is also said to have taken place, but full, authoritative and convincing statements are wanting. In the garden, D. Juarezii is exceedingly distinct from the florists' forms of D. rosea. It is usually a slenderer, taller and longer-jointed plant, with much handsomer and more delicate foliage, the leaves being narrower than in the coarse and almost ugly foliage of the old forms. It has another peculiarity of growth, which is still one of the most serious defects in the true Cactus type: the plants tend to hide some of the flowers beneath their foliage. This comes about in a curious way. At a node between two young leaves there commonly appear, at about the same time three new growths: the middle one develops into a flower with a naked stalk only 2 or 3 inches long, while the side shoots quickly overtop it and repeat the same threefold arrangement. The other most serious objection to the true Cactus type is that it does not stand shipment well and does not last so long as a cut flower as the Show dahlias.
The Decorative or Cactus Hybrid types are numerous, and their popularity is more modern. They have been largely seedlings from show flowers. Their rays are rarely, if ever, recurved at the margins. All the other types of dahlias are well defined, and a single picture of each one will represent its type with sufficient exactness. No one picture, however, can give any conception of the great variety of forms included in this more or less open horticultural section. The name Cactus Hybrid means practically "miscellaneous," and is analogous to the "Japanese" section of chrysanthemums. It is on this section and the pure Cactus type that the greatest hopes for the future of the dahlia are based.
Dahlias considered to be of true Decorative type are those possessing broad flat and nearly straight petals, arranged somewhat irregularly; but the flowers are not spherical in shape like the Show dahlia, but are inclined to be flat and massive, and are always full to the center. Dahlias of this character score a greater number of points at exhibitions.
The Colossal dahlia is the basis of much discussion, especially at exhibitions, the cause of debate being that these dahlias are in reality not classified; that is, the same variety is exhibited in one display as a Show dahlia, and in the next as a Decorative dahlia; but in reality there should be a Colossal class for this type of dahlia. This type, if it may be so called, has large cupped but not quilled rays or petals; the flowers are 5 inches and over in diameter, and spherical in shape; they therefore partake of both types, but are sufficiently different to spoil the harmony, when exhibited in either the Show or Decorative class. "Le Colosse" is the first of this type of dahlia, and hybridization has given a large number of seedlings, which are almost identical in form, shape, and size, the most prominent being at present American Beauty, Giant Purple or Royal Purple, J. K. Alexander, Surpasse Colosse, and Janne (Yellow) Colosse.
The Pompon type is a small form of the Show and Fancy types. It has the same colors and the same form, but the flowers are smaller and more abundant. As a rule, the smaller the flowers the prettier and more individual they are. The larger they are, the more they suffer by comparison with the Show type. Perhaps their greatest point is their productiveness. When profusion is the main idea, not great size and quality, the Pompons are the favorite type of dahlia for cut- flowers. The Single dahlias may be freely produced, but they are not so lasting for cut-flowers. The Single type has had many ups and downs. In the reaction against formalism, it came to the front about 1881, and for several years thereafter several hundred forms were kept distinct and they were made the chief feature of the European shows. When the dahlia first came into cultivation, its rays were relatively long, slender, acuminate, notched at the end, and with such wide spaces between the tips of the rays as to give the flower a stellate appearance. In the course of the evolution of the single type, the gardeners retained the most regular and symmetrical forms. Single dahlias with always and only eight rays were preserved.The rays of dahilias became broader and rounder, as in Fig. 1214, until finally in pedigree varieties the vacant spaces were closed up. The same mental ideals have produced the rose-petaled geraniums and the shouldered tulips. In a high-bred single dahlia there are no minute teeth or notches at the tips of the rays.
Most of the single dahlias of high pedigree have rays of uniform coloration with no secondary color at the base, but a few have a distinct ring of color at the base, often called an "eye or crown," which is sometimes yellow and rarely red or some other color. Usually the rays of a single dahlia are spread out horizontally, sometimes they bend back, and rarely they bend inwards and form a cup-shaped flower. These three forms can doubtless be separated and fixed during those periods when the interest in the Single type warrants it. Semi-double forms are frequent (Fig.1215).
Single dahlias are likely to lose some of their rays after a day or two in a vase. In cutting them it is well to choose the younger flowers. A vigorous shake often makes the older ones drop their rays. It is an easy matter to keep the seeds from forming, simply by removing the flowers as they mature, and by so doing save the strength of the plant for the production of flowers.
There are three other dahlia types of minor importance,—the Single Cactus, the Pompon Cactus and Tom Thumb. The Single Cactus type differs from the common Single type in having rays with recurved margins, which give a free and spirited appearance to the flowers. Instead of spreading put Horizontally, the rays often curve inward, forming a cup-shaped flower. This type originated with E. J. Lowe, Chepstow, England, was developed by Dobbie & Co. about 1891, and was first disseminated in 1894. The Single Cactus dahlias are very interesting and pretty. The Tom Thumb type is a miniature race of round-rayed single dahlias, which grow from 12 to 18 inches high, and are used for bedding. The type originated in England with T. W. Girdlestone, and was developed and introduced by Cheal & Sons.
The "green" dahlia (Dahlia viridiflora, Hort.) is an interesting abnormal form in which the rays are partially or wholly suppressed, and the chief feature of interest is a confused mass of green, not resembling petals at all, but evidently a multiplication of the outer involucral scales, which, in the dahlia, are green, leafy bracts. The "green" dahlia is not unhealthy: it is as strong and vigorous as any of the other forms, but very unstable and variable, producing flowers of solid green color, others of green with small cup-shaped crimson- scarlet petals intermingled, and others of solid crimson- scarlet color, and all on the same plant. This freak was pictured as long ago as 1845 in G.C., p. 626; and again in G.C. III. 30:294.
Another interesting variation which hardly ranks in present importance with the eleven types contrasted below is the laciniated form, which makes a very pretty though rather formal effect. Examples are Germania Nova, Mrs. A. W. Tait and its yellow variety among large double forms, and White Aster among the Pompons. In these cases, the notches at the tips of the rays, instead of being minute and inconspicuous, are deepened so much that they give the laciniated effect. At present this form is available in a very narrow range of colors. It is not probable that it will be an important factor in producing chrysanthemum-like forms.
Another form which baffles description, but is nevertheless very distinct, is that of Grand Duke Alexis. It is nearer the Show type than any other, but is perhaps best classed with the Cactus Hybrid section, simply because it seems advisable to keep the Show type the most sharply defined of all. It is a very flat flower, and the rays are remarkably folded, leaving a round hole at the top of each one. Up to 1909 the variety of colors of the type of Grand Duke Alexis has been increased, including the varieties Dreer White, Mrs. Roosevelt, Purple Duke, Pythias, W. W. Rawson, and Yellow Duke.
About midway between Grand Duke Alexis and the Show or cupped type is an interesting form, the "quilled" dahlia, a name which is perhaps necessary, though unfortunate. In A. D. Livoni the rays are rather tightly folded for about two-thirds of their length, leaving a round hole at the tip as in Grand Duke Alexis, but giving a peculiar whorled effect, which plainly shows the spiral arrangement of the successive tiers of rays. Among Pompons, Blumenfalter is an example of this rosette-like or quilled form, and many colors are procurable. However, the word "quilled" usually suggests a long tube with a flared opening, whereas in the form described above the margins of the ray are merely rolled tightly together, but not grown together into a thin seamless tube. Perhaps the most important variation that has not yet appeared in the dahlia is the wonderful elongation of the disk florets into long, thin, variously colored tubes which have produced such charming effects in the China aster and have culminated in the marvelous grace of many chrysanthemums. The dahlia may not be denied such possibilities, for in G.C. III. 20:339 (1896) a new dahlia was described in which the quills are really tubes for two-thirds of their length.
The Collarette dahlia is a very novel and distinct type. The flowers are single, with an additional row of short petals around the disk, which forms a frill or collar usually of a different color from the remainder of the flower. The same method obtained in the development of the Collarette dahlia as in the development of the Single dahlia, Varieties having only eight rays or petals, with the additional collar, and presenting a symmetrical and concentrated impression, were preserved. The collar consists principally of three or four smaller and more gracefully curved rays, produced at the disk, at the center of each of the eight larger rays or petals, and taking the same direction as the large rays, thus showing distinctly the golden yellow center, so pronounced in the Single dahlia. The first Collarette dahlia was President Viger, and was originated at Pare de la Tete d'Or, or in the gardens of the City of Lyons, France, then under the supervision of Professor Gerard, who was succeeded by M. Chabannes. President Viger was first shown in 1900 at the Universal Exposition, and offered for sale in 1901 by Rivorie Pere & Fils of Lyon. In 1902 appeared the variety Joseph Goujon also obtained at the Pare de la Tete d'Or, Lyon; then in 1903 Rivorie offered Etendard de Lyon and Gallia, which figured with honor for that firm. During the next ten years, from 1903 until 1913, all the known varieties of the Collarette dahlia were developed by Rivorie Pere & Fils. and appeared in the following order: 1903, Etendard de Lyon, and Gallia; 1904, Mme. LePage Viger, La Fusee, Duchesse J. Melsi D'Ehril-Barbo, Prince Galitzine, Comte Cheremeteff, and Maurice Rivoire: 1905, Exposition de Lyon Orphee, and Prince de Venosa; 1906, Merveille de Lyon, Mme. Georges Bernard, Comte Nodler, Deuil de Brazza, Princesse Olga Altieri, Corbeille de Feu, and Signorina Rosa Esengrini; 1907, Comtesse Dugon, Ami Cachat, and Volcan; 1908, Jupiter; Pluton, Pan, Etoile de Moidiere, and Mme. Chamrion; 1909, M. Mery de Montigny; 1910, Abbe Hugonnard, Comte de Vezet, Mme. Pile, Souvenir de Bel-Accueil, and Vicomtesse des Mons; 1911, General de Sonis, and Deuil du Docteur Ogier;1912, Cocarde Espagnole, Etincelant, and Stella; 1913, Geant de Lyon, Maroc, and Etoile de Monplaisir. In 1912, J. K. Alexander, a dahlia specialist in East Bridgewater, Massachusetts, succeeded in developing the first Collarette dahlia of American origin, the variety Champion; this added the red and yellow coloring to the type. Previous to 1912, three other foreign varieties, Directeur Rene Gerard, Mme. E. Poirier, and Souv. de Chabanne, found their way to America, and were offered the following year in the leading seedsmen's catalogues. The year 1913 gave a collection of nearly fifty distinct named varieties of the Collarette dahlia, including every known color in the dahlia world.
The Holland Peony-flowered dahlia is now the most popular dahlia, possessing an entirely original form, resembling the semi-double peonies; the flowers are broad, flat, somewhat irregular in form, and are produced with remarkable freedom on long stems. This type of dahlia has proved the most satisfactory for garden purposes, the plants being covered with flowers the entire season. The origin of the Holland Peony- flowered dahlia, like all other types, is uncertain, and all efforts to secure full and definite information are unfruitful. Originally the Holland Peony- flowered dahlia was grown for some years in Germany, in a mixture known as "Half-double Giant Dahlias." A Dutch grower, H. Hornsveld of Baarn, Holland, was the first to note their possibilities, and selected from these "mixed dahlias" the best varieties, from which he propagated; then he drew the attention of the public to his new varieties, which he named and offered for sale. Other growers in Holland followed his example with great success. The Holland Peony-flowered dahlia was imported to America in 1908, and simultaneously appeared in the catalogues of the leading growers and seed- men. The number increased rapidly, and in 1910 appeared new varieties of American origin, notably the new varieties originated by the W. W. Rawson Co., of Boston, Massachusetts. The most prominent varieties are the following: Andrew Carnegie (1908), Bertha Von Suttner (1908), Caesar (1911),CeciIia (1911), Dr. K. W. van Gorkum (1906), Dr. Peary (1911), Duke Henry (1906), Geisha (1908), Germania (1906), Glory of Baarn (1906), Glory of Groenekan (1907), H. Hornsveld (1907), Hugo de Vries (1907), H. J. Lovink (1911), Kaiserin Augusta Victoria (1907), King Edward (1909), King Leopold (1906), La Rainte (1907), Mannheim (1908), Merveille (1907). Miss Gladys Dawson (1908), Paul Kruger (1906), P. W. Jansen (1907), Queen Alexandra (1909), Queen Emma (1906), Queen Wilhelmina (1906), Snow Queen (1907), and Sherlock Holmes (1912).
The fragrant dahlia is the pride of the true Peony- flowered type, possessing a pleasing and agreeable odor, so long desired. The fragrant dahlia was first detected by J. Herbert Alexander, in the year 1912, on the trial-grounds of J. K. Alexander of East Bridge- water, Massachusetts; hybridization and propagation was begun immediately with the new variety, and in 1913 a collection of five fragrant dahlias appeared in Alexander's catalogue.
The main types of dahlias may perhaps be distinguished more clearly by the following scheme: The Tom Thumb Types The Single Type. Fig. 1214. The Single Cactus Type. Fig. 1213. The Pompon Type. Fig. 1211. Also called "Bouquet" and "Lilliputian." The Pompon Cactus Type. The Show Type. Fig. 1210. The Fancy Type. The Cactus Type. Figs. 1207, 1212. The Decorative Type. The Collarette Type. The Peony-flowered Type; including the fragrant dahlia. Fig. 1215.
Useful dahlias for various purposes, as they exist in North America in 1913:
Cactus dahlias, for cut-flower purposes.—Alexander, Alight, Alfred Vasey, Clara G. Stedwiek, Countess of Lonsdale, Dainty, Effective, Eureka, Floradora, Forbes Robertson, Flame, Glory of Wilts, Golden Gem, Gazelle, Gabriel, Gen. Buller, Helene, Henri Cayenx Hereward, Ivernia, Jeannette, J. H. Jackson, J. Weir Fife, Killarney, Lightship Lady Fair, Lady Colin Campbell, Lord of the Manor, Mary Service, Mrs. DeLuca, Mrs. H. L. Brouson. Mrs. Winchester, Mrs. Mortimer, Mrs. Geo. Caselton, Mme. Henri Cayeux, Mrs, MacMullan, Reine Cayeux, Rosa Starr, Reliable, Stella, Sirus, Sandy, Thomas Wilson, and Yonne Cayeux.
Cactus dahlias for exhibition purposes.—Amazon, Clincher, Diavolo, Master Carl, Mercury, Mrs. S. T. Wright, Rev. Dr. Baker, Rev. T. W. Jamieson, Royal Scarlet. Schneswitchen, Snowstorm, T. G. Baker, Wellington, Whirlwind, White Swan. Wm. Marshall, W. B. Childs.
Decorative dahlias for cut-flower purposes.—Delice, Himmlische, Jack Rose, Jeanne Charmet, John R. Baldwin, Minos, Maid of Kent, Mme. A. Lumiere, Mme. Victor Vassier, Mme. Van den Dael, Perle de la Tete D'or, Reggie, Souv. de Gustave Douzon, Wilhelm Miller.
Decorative dahlias for exhibition purposes.—American Beauty, A. E. Johnson, Blue Oban, Gigantea, Grand Duke Alexis, Gettysburg, Le Grand Manito, Le Mont Blanc, Les Alliees, Mme. Helene Charvet, Mme. Augusta Lumiere, Mademoiselle Galy Miquel, Madame Devinat, Mme. Marie, Morocco, Peerless, Perle de Ocean, Papa Charmet, Ville de Lyon, Yellow Colosse.
Peony-flowered dahlias for cut-flower purposes.—Admiration, Bertha Von Suttner, Goddess of Fame, Geisha, Marie Studholme, Mrs. A. Platt, Mrs. Jacques Futrelle, Queen Wilhelmina, and Sunrise.
Peony-flowered dahlias for exhibition purposes.— Hampton Court, King Leopold, Priscilla, Snow Queen, Solfatara, Duke Henry, and Hollandia.
Collarette dahlias for massing.—Exposition de Lyon, Maurice Rivoire, and President Viger.
Show dahlias for exhibition purposes.—Acquisition, Alice Emily, Acme of Perfection, Brown Bess, Dreer's White, Dr. Keynes, David Johnson, Emperor, Ivanhoe, Harrison Weir, Mrs. Susan Wilson, Mme. Heine Furtado, Mme. Marika Anagnostaki, Mme. Alfred Mareau, Merlin. Muriel, Norma, Nugget, Queen of Autumn, Rosebud, Stradella, Standard, W. P. Laird, and Wm. Dodds.
Among the Show dahlias that are the best for flowering are: A. D. Livoni, Arabella. Ansonia, Dr. J. P. Kirkland or Cuban Giant, Dorothy Peacock, Imperial, Miss Fox, Perfection, Storm King, and White Queen.
Show dahlia for bedding purposes.—White Bedder.
Fancy dahlias of merit.—Chorister, Chas. Turner, Dazzler, Dorothy, Distinction, Duchess of Albany, English Dandy, Eric Fisher, Gloire de Guiscard, Frank Smith, Frederick Smith, General Grant, Gold Medal, Goldsmith, Geo. Barnes, Hercules, Lea Amours de Madame, Lucy Faucett, Mme. Lily Large, Polly San- dall, Rebecca, Rev. J. B. McCamm, S. Mortimer, Sunset, and Wizard.
Pompon dahlias for borders or hedges.—Achilles, Crusoe, Darkness, Fascination, Mabel, Pure Love, Rosalie, Red Indian, Snow Clad, Vivid, and Winifred.
Pompon dahlias for exhibition purposes.—Amber Queen, Ideal, Harry, Little Mary, Rosebud, Shalii, and Spy.
Pompon dahlias for flowering purposes.—Klein Domitea, Darkest of All, Fairy Queen, Star of the East, and Spy.
Societies and shows. — The dahlia is one of about a dozen genera of plants whose horticultural value has been attested by permanently successful special societies. There are national dahlia societies in England and America. Dahlia shows are usually held the second or third week in September. On December 21, 1906, the New England Dahlia Society was chartered; this Society led to great advancement in the dahlia, holding an annual exhibition in Boston, and issuing monthly a paper known as the "Dahlia News." Great interest was fostered, and in 1913 its membership list included nearly every state in the Union, and six foreign countries. At the present date of writing the New England Dahlia Society is considering the adoption of a new charter, whereby it can become the National Society. Other societies devoted to the welfare of the dahlia have been recently formed; principally "The Dahlia Association of Seattle," "Tacoma Dahlia Society," "Inter-town Dahlia Association" in Connecticut.
Literature. — As in many other cases, the magazine literature of the dahlia is the most bulky, and, in some respects, more important than the books on the subject. C. Harman Payne published a bibliography in G.C. III. 21:329 (1897). There had been about twenty-five books devoted to the dahlia, many of them pamphlets and cheap cultural manuals. These books were mostly published from 1828 to 1867, with none in North America for nearly forty years after that date until 1896, when Lawrence K. Peacock's book, "The Dahlia," appeared. The first American treatise was by E. Sayers, published at Boston, 1839. Many interesting facts came out in 1889, the centennial year of the dahlia. A report of the National Dahlia Conference is reprinted from the Journal of the Royal Horticultural Society for 1890, but Shirley Hibberd's statements therein regarding the botany of the dahlia agree very poorly with Hemsley's revision of the genus in G.C. II. 12:437, 524, 557 (1879). In 1906 W. W. Wilmore published "The Dahlia," a handsomely illustrated American manual, valuable to both amateur and professional. The annual catalogues of the leading dahlia specialists furnish much valuable matter, and cultural hints, and are the most up-to-date issues in the dahlia line. Wilhelm Miller. J. K. Alexander.
Cultivation of the dahlia.
The dahlia has no very special or particular requirements, and yet many growers fail of the best success because the few demands are not well met.
There are four methods by which dahlias are propagated: by cuttings (the commercial method), by division of roots (the amateur's method), by grafting to perpetuate rare kinds, and by seeds, to produce new varieties.
Cuttings. — Propagation by cuttings is employed mainly by commercial growers, and though the amateur may propagate plants successfully, the attention a few cuttings would probably require is so great that it would be cheaper to buy plants. The roots are planted closely in benches in the greenhouse early in January, and cuttings are made from the young shoots as fast as they form the third or fourth set of leaves. These cuttings are carefully trimmed and placed in pure sand in the propagating-bench, using a dibble and putting the cuttings in rows about 3 inches apart and ½-1 inch between the cuttings.
The propagating-bench is made by running a flue, hot-water or steam pipes beneath an ordinary bench, and boarding up the side to confine the heat. Although there may be a difference of opinion among propagators, yet a bottom of sand heat of 65°, with the temperature of the house from 5° to 10° less, will give the best practical results. With this temperature, the cuttings will root in about two weeks, and will be far stronger than if rooted in less time with greater heat. As soon as cuttings are rooted, they are potted off into small pots and grown in a cool greenhouse until danger of frost is over, when they are planted out in the open ground. Cuttings made too far below a joint, or too late in summer, will produce flowering plants but no tubers.
Division of roots.—This is the easiest and most satisfactory way for amateurs. As the eyes are not on the tubers, but on the crown to which the tubers are attached, care must be taken that each division has at least one eye, otherwise the roots will never grow. It is, therefore, best to start the eyes by placing the roots in a warm, moist place a short time before dividing. The roots are sometimes placed in a hotbed, and shoots grown to considerable size, then set out as plants; but this plan has many drawbacks, and is not advised.
Grafting.—A very interesting, though not profitable mode of propagation is by means of grafting. The top of the tuber is cut slantingly upward, and the cutting slantingly downward, placed together and tied with raffia or any soft, handy material. They are then planted in a pot deep enough to cover the lower part of the graft with earth, and they will soon adhere if placed under a hand-glass or in a frame. Grafting is practised only for the preservation of rare and weak- growing sorts.
Seeds.—The chief use of seeds is the production of new varieties. Seeds are also used by those who chiefly desire a mass of color, and are not particularly desirous of finely formed blooms. If planted early enough indoors and transplanted to the open as soon as safe, fine masses of color can be secured before frost, and the roots of the more desirable kinds can be saved, and will give even better results the next season.
Field or garden requirements.
Dahlias are easily destroyed by high winds unless they are given a protected position, and they need plenty of air and sunlight for best results. In shaded, close, airless quarters the growth is sappy, and the flowers are poorly colored.
The soil is not so important, except in its ability to hold moisture during severe droughts. Any rich soil that will grow corn will also grow dahlias to perfection, if all other conditions are favorable. They will grow equally well in clear sand, clay or gravel, if the proper kinds and quantities of plant-food are added and well and thoroughly worked in. It is, however, unreasonable to expect dahlias or any garden plants to succeed in a hard clay, devoid of humus, easily baked and never tilled.
Feeding.—It is always best to broadcast the manure and plow or spade it into the soil; thorough spading is absolutely necessary if the manure is not well decomposed. On heavy clay or gravelly soils, loose coarse manure may be used, but on light or sandy soils, manure should always be fine and well rotted. Commercial fertilizers are also largely used, and are most valuable when used in connection with manure. Any good fertilizer, rich in ammonia and phosphoric acid, with a liberal amount of potash, will answer at the time of planting, but as a top-dressing later, nothing equals pure bone-meal and nitrate of soda, four parts bone-meal to one part soda.
Kinds of stock.—Dahlias are offered in five forms: large clumps, ordinary field-roots, pot-roots, green plants and seeds. The clumps give the best satisfaction the first year, but are entirely too large and unwieldy for anything but a local trade and exchange among amateurs. The ordinary field-roots are the most valuable, as they can be handled easily and safely, and always give satisfactory results. Pot-roots are largely used in the mailing trade, and, while they will not give as good results the first year, are valuable for shipping long distances where larger roots could not be profitably used, owing to heavy transportation charges. Green plants are mainly used to make up any deficiency in the field-crops, owing to unfavorable seasons, or an unusual demand for certain varieties.
Planting.—There is diversity of opinion as to the proper time to plant dahlias, but the writer has always found it best to plant early, and would advise planting large strong roots about two weeks before danger of frost is over. This would be, in the vicinity of Philadelphia, about April 15; and as it requires from two to three weeks for the plants to get up through the ground, there will be no danger, while the plants will bloom that much earlier. It is best, however, not to plant small roots or green plants until danger of frost is over—in the vicinity of Philadelphia, about May 1 to 10, according to the season. A good rule to follow everywhere would be to plant small roots and green plants as soon as danger of frost is past, and large roots about three weeks earlier.
Tillage.—The first requisite of successful garden cultivation is thoroughly to stir the soil to considerable depth and enrich it, if it is not already rich, by broad-casting and plowing or spading in a good coat of well-rotted manure. Too much stress cannot be placed upon the thorough preparation of the land, as it not only allows the roots to go down deep after the moisture more readily during dry weather, but affords good drainage during excessive rains. Having prepared the land as above, mark out rows 4 feet apart and 6 to 8 inches deep, and plant the roots from 18 inches to 3 feet apart in the row, according as solid rows or specimen plants are desired.
In its early stage of development, the dahlia grows very rapidly, and should be kept thoroughly tilled. But while deep tillage is beneficial during its early stages of development, it is almost fatal to the production of flowers if practised after the plants come into bloom. Therefore, when the plants begin to bloom, cease deep tillage, and stir the soil to the depth of 1 to 3 inches only, but stir it often, and never allow the surface to become hard and baked. This will not only prevent excessive evaporation of moisture and keep the under soil cool and moist, but will also prevent the destruction of immense quantities of feeding-roots.
As long as the roots supply more nourishment than is needed to support the plant, both the plant and the flowers increase in size and beauty; but as the supply gradually becomes exhausted, the plants cease growing and the flowers become much smaller. This condition is what is generally called "bloomed out," but what is really "starved out," and can easily be prevented if the proper attention is given to the plants. As soon as the flowers begin to grow smaller, broadcast around each plant a small handful of pure bone-meal, and nitrate of soda, in proportion of four parts bone to one part soda, and carefully work it into the soil.
Watering.—This is a debatable subject, and, although a judicious application of water during a severe dry spell is very beneficial, yet in nine cases out of every ten in which water is applied, a thorough stirring of the surface soil would give better results.
Many persons think Dahlias should be watered every evening, and as soon as they are up begin watering them daily unless it rains. This practice is very injurious, as it causes a rapid but soft growth, and as the soil is seldom stirred, the roots become so enfeebled that they are unable to supply the needs of the plant; as a consequence, but few buds are formed, and they generally blast before developing into flowers. In other cases, as the enthusiasm wears off, watering is stopped, probably right at the beginning of a severe drought, and the weak, pampered plants are fortunate to survive, much less bloom.
If large, strong roots are planted and the soil is kept thoroughly stirred, there will be little need of artificial watering until after the plants come out in full bloom. However, if it should become hot and dry after the dahlias come into bloom, it would be very beneficial to give them a thorough watering once each week or ten days during the continuance of the drought. But care should be taken to stir the soil to the depth of 1 to 2 inches the next day, carefully pulverizing it later in order to break the natural capillarity by which the moisture is evaporated.
The best rule to follow is not to allow the plants to suffer for want of moisture, not to water them except when they need it, but to water them thoroughly when necessary, and not to allow excessive evaporation for want of frequent stirring of the soil.
Training.—In planting the roots or tubers, place them on their sides with the eye as near the bottom as possible, and cover only 2 to 3 inches deep. As soon as the shoots appear, remove all but the strongest one, and pinch out the center of that one as soon as two or three pairs of leaves have formed, thus forcing it to branch below the level of the ground. As the plants develop, the soil is filled in gradually by subsequent hoeings. By this method the entire strength of the root and the soil is concentrated on the one shoot, causing it to grow vigorously; while the pinching back not only causes it to branch below the surface of the soil, and thus brace it against all storms, but also removes all of those imperfect, short-stemmed flowers that appear on some varieties. If the plants are pinched back low, as described, there is no danger of the branches splitting down, as the soil around them will hold them securely in place. However, when they branch above ground and are inclined to split down, drive a short stout stake near the stem and tie the branches to it. These short stakes are not to hold the plants up, but to prevent the branches splitting down when the above directions have not been followed closely.
By this method it is possible to grow dahlia blooms on stems from 18 inches to 2 feet long. It has always been thought necessary to tie dahlias to stakes to prevent them from being blown down by heavy winds. The system of staking is not only unsightly during the early stage of their growth, but is attended with considerable labor and expense. Staking, however, is unnecessary, if the directions already given are followed, as the plants will branch out below the surface of the ground, and the stems will become so heavy as to resist the strongest winds. The plants are one- third dwarfer, compact and regular in form, and produce much finer flowers on long stems well supplied with buds and foliage.
Storing the roots.—As soon as the plants are killed by frost, lift the roots, and, after removing all the soil possible from them, allow them to dry in the air for a few hours, when they should be stored in the cellar or some other cool place secure from frost. If the cellar is very dry or is not frostproof, put the roots in a barrel or box and cover completely with dry sand or some other suitable and convenient material, such as sawdust or tanbark, to prevent freezing or loss of vitality by drying or shriveling. Lawrence K. Peacock.
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Pests and diseases
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- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963