More articles about dahlias
Dahlias (Dahlia) are also known as Georgines in northern the United States and belong to the family of composite flowers (Asteraceae). They already decorated the temples of the Aztecs in their country of origin, Mexico, because the natural distribution area of all 35 species is the high plains of Mexico and Guatemala. As recent studies confirm, dahlias also had a certain significance as useful plants in Central America – their starch-rich tubers can be prepared like potatoes.
At the end of the 18th century the tuber plant found its way via Madrid to Europe. The garden dahlias known to us probably originate without exception from crosses of the two game species Dahlia pinnata and Dahlia coccineus. As the plants naturally show a high variability, several thousand varieties with almost all flower colours and often multicoloured flowers have developed over time. Only pure blue and deep violet tones do not exist. Since the flower forms are very different, the varieties are today divided into 15 different variety groups depending on their structure, such as anemone flowering dahlias or pompon dahlias.
Garden dahlias (Dahlia x hortensis) are perennial, herbaceous plants. In Central Europe, however, they can only be cultivated in the garden from the end of April to the end of November due to their sensitivity to frost. Then you dig them out, cut off the old leaves and winter the tubers in a frost-free cellar.
Dahlia leaves are opposite, partly three counted fiedrig and mostly carry a slightly sawn, partly also ciliate edge. The unfilled varieties have the typical inflorescences of the composite flowers: the fertile tubular flowers are arranged in the central basket and the coloured bracts are arranged around them. However, most varieties are so densely filled that the flower basket is hardly visible or almost all tubular flowers have their own bracts. The plants grow up to 1.30 metres high on nutrient-rich soils within one season and flower from the end of June to the first frost, depending on the time of planting.
Location and soil
The plants prefer a sunny, warm place in the garden on deep, humus- and nutrient-rich soil, not too dry.
The Dahlia Classes
Thanks to intensive breeding, there are now thousands of dahlia varieties on the market, some of which differ significantly in flower shape and colour. There are filled and unfilled variants, dahlias with pompon-like flowers, those whose flowers resemble those of water lilies and others whose pointed petals resemble a cactus. For better classification and differentiation, they were divided into 15 different dahlia classes, which we present to you in the following picture gallery on the basis of different variety examples.
Dahlias were originally typical farm garden plants, but are also increasingly used in modern flower and shrub borders. They can be combined very well with ornamental grasses and late summer perennials such as aster and coneflower. Summer flowers such as zinnias and cosmetics are also good bedding partners. Great contrasts are the rather massive looking dahlias with filigree flowering shrubs such as the magnificent candle (Gaura lindheimeri) and the Patagonian verbena (Verbena bonariensis), but also with delicate herbs such as dill and fennel. Dahlias are also suitable for larger plant pots on the terrace and are excellent cut flowers.
Dahlia tubers need a permeable soil, as the tubers rot easily when standing wet. Therefore, when planting on loamy soils, fill a hand shovel of coarse sand or clay granulate into the bottom of the planting hole for safety reasons. The tubers of the dahlias are planted so flat from the end of April at the earliest that they are covered with soil only a few centimeters high and the old stem base from the previous year still looks out slightly. After planting, it is best to sprinkle a handful of ripe compost enriched with horn shavings on the root area and place a stable planting stick on higher varieties. Avoid too tight planting – it increases the risk of fungal diseases. High grades require at least 60 centimeters clearance on all sides.
You should cut off all wilting flowers in dahlias above the next well-formed pair of leaves. New flower shoots then sprout quickly from the leaf axils. Before wintering, the entire plant is cut off a short hand’s width above the ground.
Leave your dahlias in the bed until the leaves are clearly marked by the first night frost. The tubers are still well protected during light frosts in the soil. Then cut off the plants and clear the root ball with a digging fork. Only shake off the coarse lumps of soil from the tubers. They are then labelled and should dry slightly on the outside in a frost-free, airy place. Wrap the dry tubers in wooden boxes with dry humus or sand and store the Dahlia tubers until spring, preferably in a frost-free, humid cellar at a temperature of five degrees. It is important that you only store undamaged, healthy tubers and regularly check them for rot in your winter quarters.
Further care tips
To prevent the hollow shoots from buckling in the wind, the entire bush is attached to a support bar with binding material. If the tubers are planted in pots on the windowsill from the end of February and planted from May, they often flower a month earlier.
The simplest propagation method is to divide the tubers. You can also propagate dahlias with cuttings. Use the approximately ten-centimeter-long shoots of tubers that you have driven out on the warm windowsill in early spring.
Diseases and pests
Dahlias can be affected by a whole range of diseases, but most do not occur very frequently. The most widespread are powdery mildew, leaf spot diseases and grey mould, which can be easily avoided by repeated occurrence with preventive net sulphur spraying. Also ensure an airy location and sufficient planting distance. Such problems occur more frequently in pure dahlia beds than in mixed plantations with perennials, ornamental grasses and summer flowers. One of the most common dahlia pests is the nudibranch. In addition to the usual control methods such as slug pellets, it is advisable to prefer the plants – they simply grow away from the greedy molluscs in the bed. If you have voles in your garden, you should place the tubers in underground plant baskets made of wire.
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