Dalia, Giorgina - Dahlia

Dalia, Giorgina - Dahlia

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Dalia, also commonly called Giorgina, is a perennial plant, with roots consisting of large clusters of elongated tubers, originating in Central America; there are about fifteen species of dahlia, but since their cultivation has been introduced in Europe for centuries, countless hybrids are commercially available. In spring the tubers of Giorgina produce a short stem, sometimes semi-woody, which bears numerous round-shaped leaves, with a toothed margin; in summer and for most of the autumn, thin rigid, erect stems, which carry one or some flowers, rise between the leaves. As we said there are very many giorgina hybrids, so we can have dahlias with vegetation only 20-25 cm high, like large dahlias, whose floral stems reach 150-180 cm in height. The flowers are of various shapes, generally double or stradoppi, but sometimes also simple, daisy. Like the shape of the flowers, the color is also very variable, generally in shades of red and yellow, there are also white, pink or purple dahlias.


These tuberous plants need a good insolation to bloom abundantly; so let's place them in a place where they can be reached by sunlight for at least a few hours every day, avoiding the complete shadow, which inhibits flowering. The tubers fear frost, so they are grown in pots, to be stored in a cold greenhouse during the winter; or proceed by removing the bunches of tubers from the ground in October-November, and keeping them in a dry, well-ventilated and dark place until the end of winter. After having dug them up, remember to clean the tubers from the ground, to cut off any remnants of the external vegetative part and to dust them with a good fungicide, then place them in a paper or jute bag, with little sand or sawdust, avoiding placing more tubers nearby. .

Growing the Dahlia

Dahlias are plants originating in Central America and in particular from the Mexico City region.
In the spontaneous state they are generally characterized by single-flowered corolla. They are common in areas of volcanic origin with very well drained but rather rich soil. From this it will be possible to guess that to best grow them the ideal is to reproduce as much as possible this habitat, thus giving well permeable soils, sunny positions, regular fertilization and prevention against possible pests.
These plants are provided with one of the widest fans of shapes, colors and sizes. For example, you can find pompom flowers, single flattened ones, those with the simple shape of daisy, anemone or very double and full.
Dahlias can be obtained either by seed or by vegetative means. Both methods can be good, but for some species it will be good to proceed with one procedure over another.

Dahlias watering

As soon as they are placed at home in general, the dahlias do not need watering, since in general spring is quite rainy; in case of drought we moisten the soil to favor the development of the first shoots. Afterwards water with good regularity, avoiding to leave the substratum constantly moist, and therefore providing watering only when the soil is dry. From April to September we supply fertilizer for flowering plants, dissolved in the water used for watering, every 10-12 days. Watering is completely suspended from October until the following spring, even for potted specimens.
Dahlias are fast-growing vegetables that require large amounts of water. We keep in mind that it is important to find a balance, therefore to keep the soil always damp, but not soaked because the latter condition can favor radical asphyxia.
In general we can say that during the summer and in bloom, in the absence of rains, we must intervene approximately 2 times a week.


For optimal development let's grow our dahlie in a good substratum, which consists of peat mixed with sand and little manure; a soft and well drained soil favors the development of healthy plants.

Pests and diseases

Dahlias particularly fear the rotting of tubers and also snails, which are greedy of foliage and tubers.

Meaning of dahlia

The dahlia as well as being a beautiful flower is also a species rich in history and meaning. This plant is generally used to communicate positive feelings and there are many occasions when it is recommended. First, the dahlia is a perfect gift when you want to express gratitude to a person. When, for example, you want to communicate to a person you love a feeling of closeness and esteem for some goal that person has reached the dahlia is an ideal flower. Another occasion in which you can give these flowers as gifts is to compliment your collaborators for an optimal job or for a goal achieved.
Affection and admiration are therefore the two main feelings that are expressed when a Dalia is given, a plant that was also used in the kitchen before becoming ornamental. The tuber of the Dalia in fact was cooked in some recipes of the High Middle Ages but given the poor results the culinary use was abandoned in favor of ornamental use.

Dahlia reproduction by seed

This type of propagation does not create particular difficulties (if not sometimes having to wait a lot before seeing the flowering). However, it should be pointed out that the plants obtained will rarely have the same characteristics as the ancestors, particularly in terms of color, size, shape and even vigor.
A good result can only be guaranteed by purchasing selected seeds from companies in the sector (especially in the case of hybrids).
Sowing can be carried out in a hot greenhouse or, later, in the open ground. In any case, a medium-sized but always well-drained substrate should be used. The ideal is to buy it in bags or otherwise make sure it is free of insects or other parasites.
Compost should be a mixture of peat and agricultural vermiculite. If we want to prepare it personally we can mix 1/3 of sandy and silty earth, 1/3 of peat and 1/3 of fine river sand.
The seeds should be inserted about 1 cm deep and covered with the same mixture or even just with vermiculite. You should then spray abundantly until the soil is moist. Everything will be covered with a transparent plastic bag (or kitchen film) and placed in a room or in a warm position (but not in direct light) until germination takes place. Generally 5 to 7 days are sufficient with a temperature ranging from 20 to 25 ° C. As soon as you see the leaves rising from the soil, the plastic will be removed and you will continue with light waterings (without exaggerating, to avoid rotting).

Sowing direct from the dahlia

Since the seeds of dahlia are quite large, they can be planted directly, especially if the substrate is well worked. The best period is from mid-April to the end of May. Sowing can be precise (at a distance of at least 20 cm from each other, even if much depends on the variety), or to shoot it. In fact they can be safely re-pierced because, if treated with care, they do not particularly suffer from the transplant.

Dahlia multiplication

The multiplication takes place by seed, towards the end of winter, or by division of the bunches of tubers, before abiding by proli.
Vegetative propagation
Dahlias are characterized by accumulation organs located in the roots. These can take on a fasciculate or tuberous form. Dividing these parts is a simple, fast and very common way of obtaining new plants guaranteeing, among other things, the maintenance of all the characteristics of the mother specimen.
The only care is to proceed making sure that each fragment has at least one eye. To obtain good results it is also extremely important to use sharp and clean tools (possibly disinfected by flame or bleach).
The parts we get can be planted in the garden or initially kept in a vase. In the latter case we use a very well drained and as sterile as possible compound to avoid the onset of rot where the cuts have been made (which is always good to disinfect with sulfur or other special products).
The root portions obtained by division can generally be placed again in mid-May. You will dig a hole deep enough to contain the root, taking care that the upper part (with the eye) is about 6-8 cm from the ground level. We cover with 3 cm of soft soil. When we see the stem come up, let's add it and add more land to the normal level. The distance between one plant and another is on average 60 cm, but much depends on the variety. We always refer to the indications of the nurseryman or the producer.
Propagation by cuttings
A further method is the cutting, which can be done during the vegetative period, usually at the beginning of the summer. Portions of stems must be taken with at least two pairs of leaves and at least 20 cm long. It will be placed in a draining or sterile substrate (perlite or vermiculite). This should be kept moist and the temperature around 25 ° C. Rooting takes place on average in three weeks, but much depends on the specific variety.
How to transplant well-formed seedlings (from seed, from division or from cutting) into the ground
If we have proceeded with sowing at home or in greenhouses we will have to transfer the plants to the garden. Generally the climate is not suitable until May, if we want to be sure to avoid too cold nights. The ideal is to extract all the earth bread without disturbing the roots too much. It is important that the collar maintains the same depth as when it was in the container.

The supports

Dahlias often become very tall and consequently need supports.
Their large flowers and very damp stems are easily broken by wind and rain. We then insert the rods very deeply and tie the plants without overtightening, to avoid damaging them. The ideal is to use natural raffia or soft plastic tube.

Planting dahlias

Dahlias are very greedy plants. It is therefore a good idea to work from February on very well working the soil up to at least 30 cm in depth. At this point a good amount of organic soil conditioner will be incorporated (the ideal is mature manure) which will make the substrate more aerated and the minerals more available for our tubers. We also add a slow release granular fertilizer (according to the manufacturer's instructions). We will obtain excellent results in terms of growth and flowering if the composition is as close as possible to NPK 5-10-15 (therefore with a prevalence of phosphorus and potassium).
We also note that dahlias prefer a slightly acidic substrate. We therefore correct it accordingly with sulfur or lime, if necessary.
It should also be noted that, especially in the growth phase and the winter rest period, the dahlia needs good amounts of potassium: it is essential for a good rooting and for a good accumulation of reserves before resting. If our soil were naturally lacking it will be necessary to integrate it with specific fertilizers.

Dahlia care

Dahlias are quite susceptible to diseases and insects and slug attacks. To obtain a good and above all long flowering it is necessary to dedicate constant attention to them.
It starts when the stems reach 5 to 15 cm in height. An insecticide (possibly pyrethrin) should be distributed every 15 days. We also monitor the possible appearance of mites and the presence of snails during the night.
It is also of fundamental importance to keep the area clean from weeds because these compete for nutrients, light and water and are often carriers of parasites. You can proceed with periodic hoeing or preparing a thick mulch. Very useful for this type of plants is the one based on polyethylene sheets which, in addition to avoiding weeds, warm the soil avoiding the excessive evaporation of water.

Trimming and unbuttoning

When the individuals have reached about 35 cm in height they will emit an apical bud. It is essential that both this and other neighbors are immediately removed. In this way the plant will grow more in width, creating a thick and dense bush and consequently producing many more flowers.
Later, other groups of buds will appear. To obtain large flowers it is essential to leave only the largest central one, eliminating the sides.

Dahlias bulbs

Dahlia bulbs have very particular shapes. The roots, in fact, as already mentioned above, are very large and tuberous and gathered in clusters. The typical shape of the dahlia bulbs is the one that you can see in the image and it is understood that the dahlias, but growing hands, widen their bulbs increasing their cluster dimensions.

Use as cut flowers

The climax of flowering occurs between July and August. In this period you can decide to cut the stems to use them in the compositions. We always cut with very sharp and oblique scissors. Then put them immediately in warm water. To keep their beauty longer we can use flower preservatives or a few drops of bleach and change the water every other day.

Dalia, Giorgina - Dahlia: The city of the Dahlia

If the Dahlias are your favorite flowers or if you like flowers and all the oddities related to the plant world, there is a town where you absolutely must stop. It is a Dutch town named Zundert, famous for being the city in which Van Gogh was born but also for being one of the major production centers of dahlias in the world.
In the fields of this city over 600,000 bulbs are planted in one year in as many as 31 hectares which are dedicated exclusively to the cultivation of this species.
If you decide to visit the "city of the dahlia" you will have to do it absolutely the first week of September. In this period in fact, every year since 1936, an incredible parade of flowers is taking place that is able to amaze any person.
Giant wagons halfway between engineering, art and decoration, invade the streets of the Dutch town giving a unique show. All the floats are decorated according to a main theme but above all using the flowers of Dalia. Just look at a few photos and you will be amazed.
  • Dahlia

    The dahlia, a flower belonging to the composite family, originates from Mexico but has had a very widespread use

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  • Dahlia flower

    The Dalia is a plant that does not have very great needs with regard to watering. These must be abbastan

    visit: flower dahlia
  • Dahlia in a vase

    Dahlia loves the sun and therefore abundant water intake. In summer it is especially recommended to water the soil

    visit: potted dahlia

February Ground preparation
March April Sowing, planting in a hot greenhouse
May Outdoor transfer, planting, irrigation, fertilization
June Topping, unbuttoning, irrigation, fertilization
July August Flowering, irrigation, fertilization
September End of flowering, withering
October Picking from the ground, division and drying of the roots
November-December-January Storage in a cool, dry place