Gardening Notes

Hutt News, Volume 2, Issue 33, 23 January 1930, Page 9

Gardening Notes

THE DAHLIA.

ITS HISTORY AND CULTIVATION,

The dahlia is a native of Mexico. It -was discovered in. the early part of the seventeenth century by Francisco Hernandez, a Spaniard, and described by him under the Mexican name of Acoctii, in Jris work on the plants and animals of Mexico, which, was published in IGIS, Two forms of tihe sjpecdes, viz., D. variabilis and D. erocata, were figured in that work, both having single flowers. It was named after Dr. Dahl, a "Swedish botanist, by the Abbe Cavanilles, Director of the Royal Gardens at Madrid, in 1791,

It wak introduced into England, from Spain, in 1789, by the Marchioness of

Bute, but the plants raised'oh that occasion • were lost, 'John Fraser, of Sloane-square, • Lonlon, received seeds of D. coeeinea from Paris in 1802. Ij'rom these he-fsiHaised plantsrsffpSiieh flowered in his greenhouse. Lady Holland also sent seeds to England, in 1804, but unfortunately these also were lost to cultivation.

The probable cause of the carlv failTires to grow the Dahlia Avas tiiat cultivators regarded and treated it as a "tropical plant, requiring much heat, whereas the habitat of the plant is on "the -higher plntcaux of Mexico, where the temperature is comparatively low. Hui:h>oMt mid Bonplan:!, in 1799, found Dahlias growing wild in a prairie at an altitude of 5000 feet above sea level.

• A further stock of the plant was receive 1 from Fran.ecin 1815, am] those plants thrived and it is from the stock -then imported that a great number of •our present day Dahlias originated. Although there are twenty species ,of Dahlia known to botanists and all natives of Central America, it is consiiered probablel that coeinea, Mercki amd variabilis constitute the parentage of ■almost the wJiole of our old-fashioned Dahlias, and that Yuarezii, a plant bearing a splendid loose scarlet flower, "which reached Europe in 1872, and which was named after the then President of Mexico, is- the parent of the Cactus Dahlia of the present day.

The evolution of the Da-ilia is really "wonderful when one considers it for a moment; from plants bearing single "flowers we have, -by. process of cross fertilization, raised the following distinct classes of Dahlia: —The. Single, Show and Fancy, Pompon, Decorative, Cactus, Paeony and Collarette.

Fox a great number of years the aim of Dahlia cultivation appears to have Taeen the raising, of double flowers, such as the Show and Fancy, and even as «arly as 1526 there were upwards of sixty varieties of double Dahlias in the Hoyal Horticultural Society's Gardens at •Chi'Swiek.

.Germany appears to be the dounfrry in which the Pompon varieties •of .Dahlia originated; at any rate, it was from that country that England received those varieties. .They were not recognised, as florists' flowers, ot included in the schedule of the National "Dahlia Society until 1871.

The Decoratives have been familiar in English, gardens for quite a long time, .^ome of the varieties being known for over sixty* years, Some of those varieties originated in batches of seedlings raised from seed saved from. Show Dahlias, and were selected because of their effectiveness in the. garden.

Although Dahlia Yuarezii was, introduced into Europe in 1872, .it was not till 18S0 thot it was first exhibited in England. The readiness with which raisers turned their attention to the pTodtction of varieties of Yuarezii may be understood when in 1891 the number of varieties had so increased that the National Dahlia Society .provided a class for them in the schedule of its •exhibition for that year.

The Paoonv flowei-ed Dahlas were in-

troduced in 1900, but it was not till 1905 that they were first exhibited in London. They oTginated from the intercrossing of single and cactus varieties of robust habit.

The Collarette Dahlia-is .distinguished from all tie other forms by having a frill of short, erect florets ai-ound the eentrol disc. In the year 1899, in the municipal gardens at Lyons, twp Dahlia plants produced sports having those characteristics. These sports became fixed, and were propagated, and in.-1901 were distributed as Collarette DaWias.

Since then a number of varieties have been raised, but it was not till 1910 that thy received anything like the attention due to them.

Thtro is also Dahlia imperialis, t&e Kvyai Tree Dahlia, which was discovered ir 1863, and which grows to a height of from 8 to 12 feet, according to class of sou, situation, etc. T-he .flowers' are produced in clusters, and are large, sing] 3' and bell shaped. The eolouT is ivi'ite. PROPAGATION. Ti:; Dahlia is propagated by cuttings and divisions of the tubers; a large number of new \ varieties are also raised ■each, year from seed. In dividing the ol'l tubers it is necessary to have a smsil section of the crown with each tuber. ■Ti.e best plan" is to wait till the j.-"iM>ts break into growth. before dividin.; them; you will then be sure of having a. ntmiber of properly constituted plfu it, i.e., a number of suigLe pieces o p tx.ber with" one growth to each. Propagation toy cuttings the prin•/ixjal means used for increasing the ?toek of -Da-hlia plants.

liuly in September the tubers should h> placed in an open frame in a glass

house, or on a hot bed, and partly

c:jvcrea with moist soil or sand, or a mixture of either, mixed with chopped Spftjrhruni Moss and syringed daily. T-hey will soon start into_ growth; of course if there is a nice bottom, heat jji the house, say, of about 65 deg to "■j e'eg., the growth will start much .^ocrer than in the thot bed. .', . '

Tbey may also be started in an orit'iittry cold frame, but this process is rvr'aor slow, especially if large num-b-.'rs of plants are required. When the gvvAvrhs have .attained a length of from three to four inches, they should be taken off with ajsharp knife, at a distance of about half an inc-h. from the tubers; this will pTevent injury to the buds around the base of the shoots. On the removal of the growing shoot, t-hese buds will soon start into growth, and further cuttings taken from them from time to time* If the first cuttings are very., thick' and sappy, it is best to throw them away, as they will be found to be very difficult to strike. In the preparation of the cuttings, cut away the lower portion of the stem, close up to the lower pair of "eaves, which must then be cut off close to tiie stem. The cuttings should be inserted in pots or pans, or in a bed in the house, w-hich should be made up of drainage, a layer of fine sandy loam, topped with clean, washed sand. My, own practice Jias been to take o.CE the outtings a,nd to insert them singly in thumb pots. Care nmst be. taken that the cutting is not -hung up in. the soil-, but that the end or base is made to feel the bottom of the 'hole rrjaie by the. dibber. The sand should bd pressed fairly fionly round the base of v the cutting arid ■ watered in.' The cutting pots, are placed in apportion, of the house having the same temper at ui'e as that ' from which the cuttings 'have been taken, and shaded from direct sunlight. Watering should be carefully attended to. The sand should uot be allowed to become dry, neither should the pots be waterei till sodden/ The uxfaee of the pots should be kept moist.

"When the cuttings are rooted. they': should not be allowed to remain for any length of time in the cutting pots, or they will get very thin and spindly, but should be hardened off and pottedon into four-inch, pots,'in a richer ••ompost. .

In raising Dahlias from seed,the s-eel should be sown early in September iri shallow boxes or pans. The soil should be light and porous, and tha seeds, should be sown very thinly to give them room to devolp. If this s. not done, it will be found necessary to prick the seedlings off into other pans or boxes. Keep the soil moist,, and when the plants appeal, keep them.grow. , ing without a cheek. When the plants attain a height of'from throe to four inches, they should be planted out in the bed prepared for them. If the weather is hot, it will be advisable to shade them- for a few days' till they f get a grip of the soil. Dahlias grown from seed will flower wjthin six .months from the time the seeds are sovvn, "''■'.' SITUATION. . > Practically any position, with the. exception of a shady one,- will be found to suit the" Dahlia. Select a bed, if possible, where the plants will get plenty of air and sunshine, but where they will be sheltered from the hot north and north-west winds.

SOIL. THhe best soil, in my opinion, is a well-drained, rich, heavy loam; at the same tme I may state that I have seen first-class Dahlias grown in stiff clay, also in light, sandy soil. Where the ground is new, it should be trenched to a depth of two feet, taking care that the sub-soil '.s not brought to the surface. During the trenching operations, a fairly liberal dressing pf stable manure should be added, taking care to distribute it evenly right through the soil. The •treatment of the soil here reconmiended is on the" understanding that a piece of land for Dahlia culture only is available, and- the advice given re trenching and manuring is for preparatory work in Fhe winter. The surface shoud be. left rough, so as to give the sun,-rain and frost a chance to sweeten the soil. I have found a light dressing of bone-dust in addition to the stable manure to be very bene- ;. ficial. ■■'■ • ."■•''" ;•■ -■'"■ - -:: ; :' "■■";■ "• " Where the ground has been well cultivated previously, and where the Dahlias are to be planted in mixed borders, I. would recommend that the holes for the plants should be dug, manured and filled in again some weeks previous to time of planting. A short stake or peg should b<3 used to mark the centre of each hole. '-..-. DRAINAGE. Where the land has not' been previously drained, it will be found necessary to attend to it at once. • The drains should be of sufficient depth to allow of the agricultural drain^ pipes placed at least their own depth into the cay. The pipes should then be covered with broken rubble, cinders or other similar material to a depth of from two or three inches, keeping the liner portion for the^ top next the clay or- soil. Care should be taken that none of the filling in material is sufficiently fine to- enter the drains. - The soil should then be tramped firmly so as not to permit of any subsidence at a later period - Where the soil is 0f... a heavy nature the drains should be much> closer together than where the soil is more porous; from about 12 to 15. feet apart in heavy soils, to 20 to 25 feet apart in sandy soils, should be about sufficiently "close to keep the land warm and sweet. The drains should have sufficient fall to ensure the wateT running in the pipes; two or three inches in 20 feet wiir~db. ■ The best time to do the draining is before the land is . trenched. ■■'•••"•. I would like it to be clearly' understood that where the land is sufficiently porous as to keep up a. gradual movement of the water in .the soil, and where the surplus water from watering and heavy rains is carried off in a reasonabler time, artificial .drainage is not absolutely necessary. . PLANTING. Planting for succession of bloom and for border decoration may. be made ■from early in October the middle of December. Planting out for autunin blooming and for exhibition purposes -in and around Wellington should take place duTing the third week in December. It is a good rule to have all your plants set out before Christmas. During some seasons I have found it impossible to obtain the novelties for those seasons prior* to January; in some cases one may flower ,£hem i n time, but in. most cases it will be found unsatisfactory, as the autumn shows usually take place during the last week in March, and the Dahlia requires about three months from planting out to flowering time. . \ ~. " .1 have found that in setting out the plants the most suitable distances between the rows to be 3 feet 6 inches, with the same distance between the plants in the rows. By planting in rows ,there is not the same ampujat of danger to the plants when pulling the hose, through the bed during watering, as if the intervals were broken. My. -practice is to drive in short stakes of the same thickness as those which will eventually be used for staking the plants, where the of each hole will be, and plant close up to them. In panting, I always plant sufficiently deep to allow of a depression of at least one inch in depth from, the settled level of the surface. This will facilitate watering in the earlier stages of the plants' growth ] and may be filled iin as the plant progresses. It will also ensure of the tubers being suffieietly' I deep in the soil as to prevent them breaking through the surface later on.

In selecting the plants I may state that I prefer a plant consisting of a division of-a tuber, with a single vigorous growth to a plant struck from a green cutting. My only reason for this preference is because I believe that the former will withstand the attacks of insect pests much better than the latter. STAKING AND SHAPING. As the growths progress it will necessitate their being tied on to the stakes provided for themj as they continue to grow the short stakes already alluded to at' planting time should be withdrawn; and the stakes which are to carry the plants to maturity should be substituted. As both sets of stakes are of the same thickness tie plants will not be disturbed in any way by the change. The stakes .which Ir have, always used consist of one-inch hardwood, 5 feet 6 inches in length. This will allow of their being driven about one foot into the ground. Tie with raffta or some other soft material, and as the stems increase in thickness it will be found . necessary to cut the earlier ties and retie them. As growth progresses, the thinning out of ai^xiliary growths, i.e.,lateral growths which spring. from the' axils of the leaves^ and the shaping of the plants must be attended to. My advice is> don't touch the growths springing from' the axils of the first' three pairs of leaves,'but pinch out all subsequent growths; this will throw the full flow of sap into the leading shoot, and the shoots springing from the axils of the lower leaves, seven shoots in all. This number will be found sufficient if the grower aims at blooms of exhibition standard. As the lower growths increase in length, keep them tied in singly to the same stake; an occasional long tie round the whole of the shoots should be used at intervals. DISBUDDING. As a general rule the central or terminal bud is the proper one to save; the ot-hers should be removed with a sharp knife. Before disbudding, it is advisable to examine the buds closely to make sure that they are not deformed in any way, or that they have not been eaten, by insects. The result of this examination will determine which of the buds are to be saved. SHADING. I haye seen many devices for shading the blooms, such as old umbrellas, straw hats, wire frames covered with calico, etc., etc. The best cover, in my opinipn, was one made of a band of fencing wire 12 inches in diameter, with two arches of the same glass of wire attached to it with ties of copper wire, the arches cross-ing one* another at right angles, the whole covered with gauze, such as is used by painters to strain their paint. The bend of the arched wires allowed for a depth of from 10 to 12 inches. This was held in position by being wired to two vertical stakes. Don't shade your buds until after they "have shown colour. Personally, I shade very seldom, the exception being during unusually warmAveather. , , SUBSEQUENT CULTIVATION. During, the first, month or six weeks after planting, the soil should be well worked to a depth of about two inches, , using £ne hoe freely, but at the same time taking care not to injure the plants. From, then till flowering time/ a light .hoeing pf the surface is all that will be required. MmCHING. Mulching with short grass or stable ' manure will be found very effective in keeping the ground cool and conserving moisture. WATERING. The soil should not,be allowed to become really dry, but should be kept moist. In, making thisf statement I don't intend to convey the impression that light, frequent waterings are desirable, in fact the exact opposite is what I advise^ the light waterings have a tendency to bring the roots to

the surface, where. the heat of the sun and the drying winds wiH have a most injurious e|ffecft upon them, eaustng the plants to suffer. Take my advice, when the soil is^dry give the plants a good soaking, and leave watering alone till they require it again, which will not be for five or six days even in moderately light soils; in heavy or clayey soils another soaking may not be required under nine or ten days; of course a great deal depends on the waa-, ther. When the plants are approaching

the flowering stage, it will be found advisable to hold the water off a bit; this will have a ripening .effect on the wood.