Among the best known decorative plants, the Dahlia certainly occupies a prominent place. In fact, it is highly appreciated for the garish beauty of its flowers and often used for ornamental purposes to embellish flowerbeds and sills.
Dahlias are native to Mexico and belong to the Asteraceae family. The name refers to the similarity that the flowers have with a star surrounded by rays.
The scientific name is dahlia and was given by Antonio José de Cavanilles, director of the Royal Botanical Garden of Madrid, to honor the botanist Andreas Dahl, a pupil of Linnaeus.
But let’s go in order because the history of these beautiful plants has ancient origins and is really interesting.
The dahlias were already known to the Aztecs, who utilized them mainly as food and medicinal plant against the epilepsy or as a mosquito repellent.
It was then introduced in Europe by the Spanish conquerors, who wanted to grow them as a substitute for potatoes. But, if the westerners found the taste of the tuber unpleasant and considered it of little alimentary value, they guessed, however, its decorative potentialities and destined it for ornamental purposes.
Starting from the XVIII century, therefore, an intense activity of selection and hybridization of this plant began, which has led, to our days, to the existence of more than 30 species of dahlias and about 20.000 cultivars.
Dahlias: Botanical Characteristics
Dahlias are bushy perennial plants, formed by a tuberous root from which long cylindrical and hollow herbaceous stems originate, with a height that can vary from 20 cm to 2 m.
It has numerous fleshy leaves of pinnate shape and in some toothed varieties, bright green or dark green and, also, purple.
It blooms from June until late autumn, presenting flowers of the most varied shapes and sizes.
The particularity of dahlia flowers is that they are composite, i.e. formed by a central inflorescence, called a disc, surrounded by a corolla which everyone calls petals, but which in reality are also flowers, called ray florets. They can be big or small, single or double, simple, ball shaped, daisy or pompon-shaped.
Also the colors can vary and we find them white, yellow, orange, pink, dark pink, red, lavender, burgundy, pastel colors, bronze, but also variegated, mottled and bicolored. The only color that we have not been able to recreate is pure blue.
Dahlias: Most Common Varieties
There are different varieties of dahlias, divided according to the type and shape of the flower. The most common in Italy are:
- Single-flowered dahlias, the most common, with rounded or pointed yellow or red flowers, formed by a central disc and a single round of small ray flowers. They have a medium height, but there are also mignon varieties.
- Collar-shaped dahlias, so called because they have a circle of small flowers similar to a collar inside the central disc, around which a single round of large, flattened flowers develops. They are generally large plants.
- Water-lily shaped dahlias, they resemble, in fact, the water-lily flower, they are double, symmetrical, with the flowers of the outer ray slightly curved and flattened. Particularly suitable for creating bouquets.
- Anemone-shaped dahlias, the most particular, because the disc is absent and the centre of the flower is composed of small elongated tubular flowers, surrounded by one or more rows of flat ray flowers of variable length.
- Ball-shaped dahlias, spherical in shape, with the radius flowers rounded and facing inwards.
- Pompon dahlias, which resemble the shape of a pompom, smaller than ball dahlias, have a spherical shape with the ray florets curved inwards to form a kind of hive.
- Cactus dahlias, very characteristic, with the ray florets long, pointed and turned upwards.
- Decorative dahlias, the most classic, do not have a visible central disc and the ray florets are cylindrical and curved inwards. There are all sizes: giant, large, medium, small and mignon.
Dahlias are not very rustic and quite delicate plants and can be grown both in open ground and in pots or planters, especially dwarf varieties.
The dahlias grow vigorously in humid soils, not too compact, rich of organic substance, but, above all, well drained with sand or other draining material.
Dahlias love sunny places, but they can stand half shade.
They also tolerate sultry heat, but do not survive the intense cold and want to grow in a place sheltered from the wind.
Dahlias’ bulbs should be planted from mid-March to May, depending on the area, when there is no longer any risk of frost.
- Before planting the bulb, spade the soil to remove stones and weeds and then add mature manure.
- Bury the bulbs 10-15 cm deep and 20-80 cm apart depending on the variety.
- Then compress the soil slightly and water abundantly.
- You can also let the seedlings develop in a greenhouse or in a covered place, putting them in wet peat, and then plant them when they are strong enough. This will also allow you to anticipate the flowering.
- If you have decided to grow your dahlias in a pot, choose one at least 30 cm deep and plant the tuber 4-6 cm deep.
How And When To Water A Dahlia
The dahlias require abundant and regular watering, even daily, especially during the summer period and the flowering, taking also into account the natural rainfall, if the plant is cultivated in open land.
In autumn and winter, the water supply is to be reduced or eliminated completely, in order to avoid water stagnations and the rottenness of the roots.
Dahlias need constant fertilization.
Especially during the vegetative period, it is necessary to administer liquid fertilizer based on phosphorus to be diluted in watering water or in granular slow release form to be distributed evenly on the soil at the base of the plant.
During the vegetative period, some weeding and hoeing operations are to be done, about every two months.
Dahlias in Winter
If you live in an area of Italy where winters are harsh and the ground is frozen, at the end of October-early November you have to uproot the bulbs from the ground, because dahlias cannot stand the frost.
- Prune the stems 10 cm above ground. To cut the stems cleanly, always use suitable tools such as shears or gardening scissors that have been thoroughly cleaned before use.
- Then dig out the soil and gently lift the bulb.
- Clean it well off the ground and leave it to dry for a few days outdoors.
- Now put the bulbs in wooden boxes, sprinkle them with a powdered fungicide and then with dry peat and sand and store them in a dry, dark and ventilated place until the end of the winter season.
- In spring, put the bulbs back into a moist soil mixed with peat.
- When they become strong enough, put them back into the garden.
Also for potted specimens you can follow the same procedures as above, but much more simply, you can move the dahlia plants to a well protected and sheltered place where the winter cold doesn’t come.
Dahlias: Pests and Diseases
Dahlias may be attacked by aphids or the red spider mite, which can be fought with a special insecticide.
It may also be useful to use some anti-slug products because these animals are particularly fond of dahlias.
Above all, water stagnation, which can cause rotting at the roots and the consequent death of the plant, should be avoided.
Dahlias, with all their different shapes and shades of colors, with their beauty and complexity, are perfect to represent women.
If you receive it as a gift, or want to give it as a gift, it is an expression of admiration for femininity and elegance.
But it is also a symbol of gratitude for the person to whom it is offered.