Dahlias are half-hardy perennials, originally from Mexico, and now very popular in the United States. Very adaptable, they grow well in any type of soil. They are versatile, being used for garden decoration, cut flowers, floral art, and exhibition. Few flowers can match them for their wide range of brilliant colors, their wide variety of shapes and sizes, and their long flowering period. They tolerate extremes of climate and, even in a poor season, some kinds will produce over one hundred flowers.
Classification In height dahlias range from the Lilliput type, I ft. high, to the more normal types which can reach a height of over 5 ft., although the average is about 3 1/2 ft. The sizes of the blooms vary tremendously, from about 1 in. across to over 14 in.
There are fourteen groups as follows:
INCURVED CACTUS Fully double flowers with the margins of the majority of the floral rays fully revolute for 1/2 more of their length and the tips of the rays curving toward the center of the flower.
STRAIGHT CACTUS Fully double flowers with the margins of the majority of the floral rays fully revolute for 1/2 their length or more, the rays being straight, slightly incurved or recurved.
SEMI-CACTUS DAHLIA Fully double flowers with the margins of the majority of the floral rays fully revolute for fewer than+ their length and the rays broad below.
BALL DAHLIAS Fully double flowers ball-shaped or slightly flattened. Floral rays blunt or round at tips and quilled or with margins involute for more than 1/2 the length of the ray in a spiral arrangement, the flowers over 3 1/2 in. in diameter.
MINIATURE DAHLIAS All dahlias which normally produce flowers that do not exceed 4 in. in diameter. Pompoms excluded, to be classified according to the foregoing description.
Miniature Single, Miniature Peony, Miniature Straight Cactus, Miniature Semi-cactus, Miniature Formal Decorative, Miniature Informal Decorative.
POMPOM DAHLIAS Having the same character istics as Ball Dahlias but for show purposes not more than 2 in. in diameter.
SINGLE DAHLIAS Open-centered flowers with only one row of ray florets with the margins flat or nearly so, regardless of the number of florets.
MIGNON Single flowers, the plants approximately 18 in. in height.
ORCHID-FLOWERING DAHLIAS Flowers as in single dahlias excepting that the rays are more or less tubular by the involution of the margins.
ANEMONE DAHLIAS Open-centered flowers, with only one row of ray florets, regardless of form or number of the florets, with the tubular disc florets elongated, forming a pincushion effect.
COLLARETTE DAHLIAS Open centered flowers with only one row of ray florets, with the addition of a different color, forming a collar around the disc.
PAEONY DAHLIAS Open centered flowers with two to five rows of ray florets with or without the addition of smaller curled or twisted floral rays around the disc.
FORMAL DECORATIVE DAHLIAS Fully double flowers, with the margins of the floral rays slightly or not at all revolute, the ray generally broad, either pointed or rounded at tips, with outer rays tending to recurve and central rays tending to be cupped; and the majority of all floral rays in a regular arrangement.
INFORMAL DECORATIVE DAHLIAS Fully double flowers, with the margins of the majority of the floral rays slightly or not at all revolute, the rays generally long, twisted or pointed and usually irregular in arrangement.
Planting location
Dahlias prefer an open sunny position but will still grow well in a partially shaded spot, away from trees. They look glorious when massed in a bed or border by themselves. They also fit in well with other plants in the herbaceous border, if they are placed carefully to use their various heights and colors to best effect. The 1-ft. tall dwarf kinds will add summer color to the rock garden or can be planted in a bed in a retaining wall or even in a window box. Planted in tubs or other containers, they will brighten up a patio, terrace or other paved area.
Soil Cultivation
Single digging is all that is necessary. This should be done in late fall or early winter on heavy soil, leaving the ground rough for the snow and frost to break it down; light soils can be left until early spring. Every soil benefits from the addition of humus-forming material such as farmyard manure, peatmoss, horse manure, leaf mold, compost, straw, seaweed, etc., dug into the top few inches.
A month or so before planting, the soil should be broken down to a reasonable tilth and a top dressing of either bonemeal or a general fertilizer should be raked into the top couple of inches of soil.
Planting Out
Dahlias can be grown either from tubers or green plants. Tubers are the roots that have formed at the base of a plant grown the previous season. They can be planted from early May onwards. Space the tall types about 21 ft. apart, the dwarf bedding types ti ft. apart, and the Dwarf types I ft. A stout 4 ft. stake or cane is needed for the taller types and these are put in position first. Plant the tubers 6-in. deep, just in front of the cane. On poor soil put in a couple of handfuls of a mixture of peatmoss and a little general fertilizer, into the hole and put the tuber on this, stem upwards, and fill in the hole with fine soil. Once the shoots appear above ground they are treated exactly as green plants.
Green plants are planted as soon as all danger of frost is over. Canes are put in position first and a hole slightly larger than the plant rootball is taken out just in front of the cane.) A planting mixture of peatmoss and fertilizer will help to get the plants away to a flying start on poor soil. Place the plant in the hole and fill it in with soil. Tie the plant loosely to the cane with soft twine then water the plants in well. Place a few slug pellets around each plant.
Summer Management
For the first three or four weeks after planting, hoe the soil between the plants to keep down the weeds. When the plants have developed five or six pairs of leaves, pinch out the growing tip to promote bushy growth. As the side shoots develop after this stopping they will need to be kept tied into the cane.
The soil around the plants should never be allowed to dry out. Dahlias benefit greatly from the application of a mulch which will lessen the need for watering. Apply this in early July to a depth of about 4 in., completely covering the soil around the plants.
Flowering
The first flowers should begin to appear about mid or late July. Better quality flowers can be obtained by disbud ding, which means removing the two small side buds which appear either side of the main or terminal bud. Also remove the two side shoots which appear at the joint of the pair of leaves below the flowering bud. Left to themselves dahlias produce dozens of small poor quality flowers on short stems; a little light disbudding and de-shooting makes an amazing difference.
Faded blooms should be removed to en, sure continuation of flowering. This is particularly important with the single-flow ering types which form seed heads very quickly. When cutting blooms for the house use a sharp knife, make a long slanting cut and plunge the stem immediately in deep water; cut in this way, dahlias should easily last a week. Cut as many blooms as you like, as often as you like.
Give the plants an occasional foliar feed. Make sure that all the plants to be saved for next year are clearly labeled with their name (if known), or type and color.
Lifting and Storing
Lifting The tubers which have formed at the base of the plants will need to be lifted and stored for the winter. After the frost has killed the foliage cut through the main stem about 6 in. above soil level. With a fork loosen the soil round the tuber then push the fork underneath and lift the tuber.
Remove surplus soil from the roots and place them stem downwards in a greenhouse, shed, garage, or spare room for about ten days to dry. While they are drying the tubers can be prepared for storage. Trim off the thin stringy roots from the ends of the tubers and cut the stem down to about 2 in. Any damaged ends of the roots should be trimmed away and the cut surface dusted with either green sulfur or a mixture of lime and flowers of sulfur in equal parts. Tie the label securely to the stem.
Storing If a frost-free garage, shed or spare room is available, place the tubers in shallow boxes of peatmoss or dry soil. A cool cellar makes an ideal storage place. Where frost protection cannot be guaranteed, protect the tubers by placing them in stout wooden or cardboard boxes filled with an insulating material such as dry soil, sand, ashes, straw or sawdust.
Inspect the tubers once or twice while they are in store to make sure they are sound. Feel each tuber; if any parts are soft and brown this indicates rot which will have to be trimmed away and the cut surface dusted with sulfur/lime powder. Any tubers with a white fluffy deposit (mildew) will need to be wiped clean with a dry cloth and dusted with sulfur/lime.
Propagation
Dahlias are very easy to propagate, whether from seed, division of tubers, or by cuttings. Sowing seed Plants will not reproduce true to type or color from seed, except for the single Coltness type and the semi-double dwarf bedders.
Sow the seed in March in a heated greenhouse, thinly, in pans or flats of general seed compost or one of the soilless seed composts, covering the seed with a in. of compost. Once they germinate they should be pricked out 24 to a flat. Grow the plants on coolly and in April move them to a cold frame to harden off before planting them out in late May or early June.
Dividing tubers
A dahlia tuber consists of a stem which is attached to the crown or collar where the eyes or buds are situated ; swollen, potato-like tubers are attached to the crown. There are two types of tuber; the ground tuber is usually quite large and is formed at the base of a plant grown outdoors without restriction; the pot tuber is small and compact and is formed at the base of cuttings grown throughout the season in pots.
Before dividing the tuber the eyes must be visible and are coaxed into life by placing the tubers in moist peatmoss or compost in late March or early April in flats which are placed either in a greenhouse or cold frame or on a sunny windowsill in the house. Once the eyes are visible, cut down the center of the stem between the buds, right through the tuber. Further division may be possible, depending on the size of tuber and the position of the eyes, but each piece to be planted must contain a portion of stem attached to a piece of the crown bearing an eye, and at least one portion of swollen root or tuber. The divisions can either be planted out in early May or grown on in flats in the greenhouse and planted out in late May.
Taking Cuttings
Large numbers of cuttings can be taken from dahlia tubers; they root easily in a warm greenhouse in a minimum temperature of 60°F . If any tubers show signs of rot or mildew, treat them as described earlier. The tubers are boxed up in moist peatmoss or compost, or they can be bedded down on the open greenhouse bench, if possible, over some form of bottom heat. Keep the compost moist.
The cuttings are taken when the shoots are 3-4 in. long and are normally placed round the sides of a pot or pan or placed in a flat in rows.
With a clean sharp knife cut through the shoot just below the lowest leaf joint. Trim off the lower leaves, dip the end of the cutting in a hormone rooting powder then place the cutting 1 in. deep in the compost. Space the cuttings so that the leaves are just clear of each other and water lightly. Place the cuttings in a propagating frame, or bed the pots in moist peatmoss on the open bench and provide shade.
Spray the cuttings with a fungicide to prevent damping off and after a day or so allow them a free flow of air. To lessen the risk of flagging, spray the cuttings with tepid water twice daily until rooting takes place in about 14 days.
Pot the rooted cuttings singly into 3 1/2-in. pots of general compost or a peat-based compost. Keep the plants in a shady spot in the greenhouse for a day or so before placing them on a shelf near the glass, keeping the greenhouse well ventilated. In April remove the plants to a cold frame, keep the sash closed for a couple of days then progressively allow more ventilation until, towards planting out time in late May or, in the colder areas, in early June, the lights can be left off completely. At all times protect the plants from extreme cold.
Recommended Dahlia Varieties
Decorative Dahlias
Giant:
‘Arthur Godfrey’. A strong grower with very large blooms which are red with orange shading;
‘Hamad Girl’, lavender pink, easy to grow;
‘Hollands Festival’, orange with white tips;
‘Ohcho’, creamy-yellow very vigorous.
Large:
‘Ben Hill’, red blooms to top quality;
‘Jacqueline Kennedy’, rich purple;
‘Leone’, white suffused lavender with deeper lavender centers.
Medium:
‘After You’ produces masses of yellow flowers good for cutting or exhibition;
‘Cherokee Charm’, clear pink, flowers early in the season;
‘First Lady’, Dresden yellow, reflex shape;
‘Golden Treasure’, gold blooms, for
cut flowers or exhibition;
‘Purple Velvet’, purple with a velvety sheen and outstanding exhibition variety;
‘Sterling Silver’, an outstanding white variety.
Small:
‘Early Bird’, purple and white, early flowering;
‘Fete D’Orange’, orange blooms which appear early in the season;
‘Lions International’, rose-pink and outstanding variety;
‘Southern Beauty’, white suffused purple, a good exhibition variety;
‘Tammy
Foondle’, primrose yellow;
‘Ventura’, yellow, good for exhibition or cutting.
Miniature:
‘Bobo’, bronze suffused with scarlet at tips of petals;
‘Silver Spring’, pink, fine for exhibition;
‘Treasure’, pink.
Cactus Dahlias
Giant: ‘Clarion Royalty’, purple, strong growing, an excellent exhibition variety.
Large:
‘Frontispiece’, white;
‘Goldie’, golden apricot, an outstanding variety.
Medium:
‘Alabama Melody’, clear pink, early flowering, a good exhibition variety.
‘Extravaganza’, scarlet, early blooms of good quality;
‘Krijnens Jubileum’, yellow, strong growing and early flowering
Small:
‘Dicky Bill’, pink with red streaking, very early;
‘Maude Crawford’, yellow, flowers early and profusely;
‘Orange Parfait’, orange-red, low growing;
‘Shawnee Lavender’, early, flowers dark pink;
‘Sonnet’, yellow;
‘Sundown’, petals white tipped purple. A good cut flower
Semi Cactus Dahlias:
Giant:
‘Arab Queen’, coral pink flower, yellow center;
‘Super’, salmon red, one of the largest;
‘Mary Elizabeth’, dark red, strong growing
Medium:
‘Extravaganza’, scarlet, early flowering;
‘Fair Lady’, rose and white, good for cutting;
‘Lady Elaine’, white, good for exhibition;
‘Mrs D. Bortels’, orange, a prolific bloomer;
‘Shawnee Dream’, pink, a good exhibition variety
Small:
‘Country Music’, yellow;
‘Herbert Smith’, pink, an excellent show variety and first class for cutting;
‘Poise’, red and white, very striking color combination
Ball Dahlias
‘Butterball’, light yellow, strong growing;
‘Clyde Carraway’, very vigorous, golden streaked red;
‘Pat’N Dee’, white
Pompom:
‘Bronze Beauty’, bronze and orange, very strong growing;
‘Clarisse’, golden orange, fine for cutting or exhibition;
‘Willos Violet’, deep purple on lighter ground.
Anemone Flowered:
‘Comet’, deep velvet blood red;
‘Vera Higgins’, fawn and orange.
Colleretts:
‘Coincident’, cherry red and yellow;
‘La Cierva’, purple.
Paeony Flowered:
‘Bishop of Llandaff’, scarlet with dark foliage.
Single Flowered:
‘Bright Flash’, red, vigorous grower;
‘Tango Century’, bronze shades.
