DAHLIA cultivation skills

Dahlias have an interesting history. The first tubers arrived in Europe at the end of the 18th century-sent over to Madrid by the Spanish settlers in Mexico. Andreas Dahl (after whom the plant is named) regarded it as a vegetable rather than a garden flower, but interest switched from the edible tubers to the blooms when the first varieties with large, double flowers were bred in Belgium in 1815. Some of M Donckelaar’s novelties were sent to England, and the craze began.

Within a few years nearly every colour we now admire had been introduced, and Victorian catalogues listed hundreds of varieties. The favourites in those days were the Ball and Small Decorative Dahlias – today it is the Large Decorative and Cactus varieties which capture the public fancy. Fashions change, but the popularity of this late summer flower continues to increase.

The reasons for this devotion to the Dahlia are fairly obvious. First of all, the skill of the breeders in England, Holland, Germany, Australia and America has produced a range of sizes and colours unmatched in the world of garden flowers. Plants ranging from dwarf bedders 1 ft high to giants taller than a man – flowers ranging in size from a 2p coin to the largest dinner plate.

Equally important is the time of flowering. From the end of July to the first frosts, Dahlias provide large orbs of colour when so many flowers are past their best. Above all, the Dahlia is an accommodating plant. It likes a good loam but will grow almost anywhere. It relishes sunshine, but can still do well in partial shade. A bed just for Dahlias is really the ideal way of growing them, but they are quite at home in the herbaceous border.. .or even the rockery for dwarf bedding varieties.

An important virtue is the way they put up with the novice or casual gardener. For him, growing Dahlias is a matter of planting the tubers which were dug up last year and stored in the garage. This planting is carried out when the season of frosts is past, and if no tubers are available then a trip to the garden centre offers a wide range of pot tubers or rooted cuttings. With planting out of the way, it’s just a matter of staking when the stems threaten to fall over and the foliage is sprayed when blackfly becomes a nuisance. Even with such simple treatment a surprisingly good display can be obtained.

But it need not be an ‘easy’ plant. For the enthusiast the growing of Dahlias is an exacting and absorbing hobby. There are soil mixtures and composts to prepare in winter, cuttings to raise from tubers, growing points to pinch out, fertilizer to apply, side shoots to remove, plants to disbud, roots to be kept moist and show blooms to stage. There are many challenges for the enthusiast – there is the world record 21 in. bloom to beat, the elusive blue Dahlia to raise and a variety of show awards to win.

But most of the Dahlias will continue to be grown by ordinary gardeners who do not regard growing this plant as their hobby. For them the Dahlia is used to bridge the late summer colour gap in the herbaceous border . . . plus the added benefit of obtaining cut flowers which are large enough to impress the neighbours.

DAHLIA PLANTING MATERIAL

GROUND TUBERS

Usual source: Own garden, dug up in previous autumn and stored over winter.

Every couple of years tubers should be carefully divided. Make sure that each division has a piece of stem with swollen tubers attached.

POT TUBERS

Usual source: Garden shop or mail order nursery.

Pot tubers are convenient and easy-to-handle planting mater-ial, but it is more economical to use them to provide cuttings which are then rooted for planting out.

ROOTED CUTTINGS

Usual source: Garden shop or mail order nursery or

Home-grown – Tubers are planted in moist compost in March under glass to provide 3 in. shoots. These are severed and trimmed, then used as cuttings for potting up and then planting out.

SEEDS

Usual source: Garden shop or mail order nursery.

Bedding varieties can be raised this way. Sow in gentle heat (60°F) in late March, plant out in late May. The

Flowering period: is from late July to November.

FLOWER SIZE

Some catalogues use words to describe the bloom diameters of well-grown Decorative and Cactus varieties. The key below will guide you in making your choice.

Giant More than 10 in.

Large 8-10 in.

Medium 6-8 in.

Small 4-6 in.

Miniature Less than 4 in.

PLANT HEIGHT

Some catalogues use words to describe the average height of a variety grown under good conditions. Do remember that the stated height is only an average – the actual height achieved by a plant in your garden will depend on the location, weather and cultural conditions.

Tall Border variety More than 4 ft

Medium Border variety 3-4 ft

Small Border variety Less than 3 ft

Bedding variety Less than 2 ft

Lilliput variety 1 ft or less

HOBBY PLANTS

PLANTING DISTANCES

Tall Border varieties 3 ft

Medium Border varieties 2 ft

Bedding varieties 1-1.5 ft

PLANTING TUBERS

Plant dormant tubers in mid April – wait until early May in cold northern districts. Dig a hole about 6 in. deep with a spade. Place the tuber in the hole and cover with fine soil. The crown of the tuber should be about 3 in. below the surface. Make sure the soil fills the spaces between the tubers-after filling press the soilfirmlywithyourfingers. Finally, label the stake with the name of the variety. There is no need to water at this stage.

Use a 1 in. square wooden stake for tall varieties – stout bamboo for smaller types. Insert the stake to a depth of 12-15 in. before planting. The height should be about 1 ft less than that expected for the plant. When growth reaches 9 in., tie the main stem loosely to the stake, using soft string. Make additional ties as the plant grows. For plants with several main stems a few extra stakes may be required.

MULCHING

Do not hoe as plants are shallow rooting. Keep weeds out and moisture in by applying a 2 in. layer of peat or compost around the plants in early July.

SITE AND SOIL

Pick a spot which receives at least a few hours sunshine on a bright day. Do not plant under trees nor in soil which gets waterlogged. Medium loam is ideal, but most soils are satisfactory. In autumn or winter dig in plenty of organic matter such as compost or well-rotted manure – there is no need to dig deeper than one spade’s depth. Rake in 4 oz of Bone Meal per sq. yd. After digging.

DEAD-HEADING

The regular removal of faded blooms will prolong the flowering life of the plant.

PLANTING ROOTED CUTTINGS

Plant in late May in southern districts – wait until early June in the north. Water pots about an hour before planting. Use a trowel to dig a hole which is larger than the soil ball of the cutting. Water in a couple of days after planting. Treat tubers bearing shoots as rooted cuttings.

WATERING & FEEDING Water thoroughly during dry spells. Once the buds have appeared it will be necessary to water every few days if rain does not fall. Feed occasionally from July until early September – use a liquid fertilizer, such as Instant Bio, which has a higher potash than nitrogen content.

PESTS & DISEASES

The worst pests – aphids, capsids, red spider mites, caterpillars and earwigs are easily controlled by using a general-purpose systemic spray such as Long-last. In wireworm-infested soil rake in Bromophos before planting. In a wet summer sprinkle Slug Pellets around young shoots. Diseases are rarely serious but two (mosaic and spotted wilt) are due to viruses and there is no cure. Lift the plants and burn. Remember to spray against aphids, which are the virus carriers.

STORING TUBERS

When the first frosts have blackened the foliage cut off the stems about 6 in. above the ground. Gently fork out the tubers and discard surplus soil and broken roots. Stand tubers upside down for a week to drain off excess moisture. Then place them on a layer of peat in deep boxes and cover the roots (not crowns) with more peat. Store in a cool but frost-free place.

DISBUDDING

For larger (but fewer) flowers it is necessary to re-move the sidebuds, leaving only the terminal flower bud.

SIDE-SHOOTING

Long-stemmed plants are needed for indoor décoration and exhibiting – snap away unwanted laterals from the main stem about 2 weeks after stopping.

STOPPING

To increase bushi-ness it is necessary to pinch out the tips of the main stems about 3 weeks after planting.

ANEMONE-FLOWERED

One or more rings of ray florets. Central group of tubular florets. Height2-3ft.Bloomsupto4in. Examples are ‘Vera Higgins’ (bronze), ‘Lucy’ (purple and yellow) and ‘Comet’ (red)

Tubular Floret

SINGLE-FLOWERED

One ring of ray florets. Central group of disc florets. Height 1.5-2 ft. Blooms up to 4 in. Examples are ‘Yellow Ham-mer’ (yellow), ‘Princess Marie Jose’ (pink) and ‘Orangeade’ (reddish orange)

DECORATIVE

Fully double. Flat ray florets are broad and blunt-ended. Height 3-5ft.Blooms3-10in.ormore. Examples are Giant – ‘Jocondo’ (purple), Large – ‘Thames Valley’ (yellow), Medium – ‘Terpo’ (red), Small – ‘Gerrie Hoek’ (pink) and Miniature – ‘David Howard’ (orange)

COLLERETTE

One outer ring of flat ray florets plusan inner ring of collarflorets and a central group of disc florets. Height 2.5-4 ft. Blooms up to 4 in. Examples are ‘La Gioconda’ (scarlet and gold), ‘Claire de Lune’ (yellow and cream) and ‘Chimborazo’ (red and cream)

Dahlia blooms are made up of miniature flowers known as florets. The types of florets present are a key to identification.

Involute Ray Floret (Rolled inwards)

Revolute Ray Floret

I Collar FloreT (Rolled outwards)

PAEONY-FLOWERED

BALL Fully double; ball-shaped – often flattened. Involute ray florets are blunt- or round-ended. Height 3-4 ft. Blooms 3-6 in. Examples are ‘Doreen Hayes’ (red), ‘Crichton Honey’ (peach and red) and ‘Esmonde’ (yellow)

Two or more rings of flattened ray florets. Central group of disc florets. Height 2% -4 ft. Blooms up to 5 in. Examples are ‘Bishop of Llandaff’ (red), ‘Sympnonia’ (vermilion) and ‘Fascination’ (purple)

POMPON

Fully double; globe-shaped. Involute ray florets are blunt- or round-ended. Height 3-4 ft. Blooms less than 2 in. Exam-ples are ‘Hallmark’ (lavender), ‘Willo’s Violet’ (pale purple) and ‘Noreen’ (pink)

CACTUS

Fully double. Revolute ray florets are narrow and pointed. Height 3-5 ft. Blooms 3-10 in. or more. Examples are Giant – ‘Danny’ (pink), Large – ‘Irish Visit’ (red), Medium – Appleblossom’ (pale pink), Small – ‘Doris Day’ (red) and Miniature – ‘Pirouette’ (yellow)

SEMI-CACTUS

Fully double. Pointed ray florets are revolute for half their length or less. Broader than Cactus Dahlia petals. Height 3-5 ft. Blooms 3-10 in. or more. Examples are Giant – ‘Hamari Boy’ (yellow), Large – ‘Nantenan’(yellow), Medium – ‘Autumn Fire’ (orange-red), Small – ‘White Swallow’ (white) and Miniature-’Yellow Mood’ (yellow)

MISCELLANEOUS

Flower form not belonging to Groups I-IX. Examples are Orchid-flowered Dahlias such as ‘Giraffe’ (yellow and red), Incurved Chrysanthemum-flowered Dahlias such as ‘Andries Wonder’ (salmon), and Star Dahlias which are now rarely seen

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