Dalia, Giorgina - Dahlia

Dalia, Giorgina - Dahlia

The dahlia

The dahlia, also commonly called Giorgina, is a perennial plant, with roots made up of large clusters of elongated tubers, native to Central America; there are about fifteen species of dahlia, but as their cultivation has been introduced in Europe for centuries, countless hybrids are commercially available. In spring Giorgina's tubers produce a short stem, sometimes semi-woody, which bears numerous roundish leaves with a toothed margin; in summer and for most of autumn thin stiff, erect stems rise between the leaves, bearing one or a few flowers. As we said, there are many hybrids of giorgina, therefore we can have dahlias with vegetation only 20-25 cm tall, as well as large dahlias, whose floral stems reach 150-180 cm in height. The flowers are of various shapes, generally double or very double, 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 amount of sunlight to bloom abundantly; therefore let's place them in a place where they can be reached by sunlight for at least a few hours every day, avoiding complete shade, which inhibits flowering. The tubers fear frost, therefore they are grown in pots, to be placed in a cold greenhouse during the winter; or we proceed by extracting the clusters 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 unearthed them, remember to clean the tubers from the ground, cut any remnants of the external vegetative part and sprinkle them with a good fungicide, then put them in a paper or jute bag, with a little sand or sawdust, avoiding placing more tubers close together. .

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Cultivate the Dahlia

Dahlias are plants native to Central America and in particular to the Mexico City region.

In the spontaneous state they are generally characterized by a single corolla flower. They are common in areas of volcanic origin with very well drained but rather rich soil. From this it can be understood that in order to grow them in the best possible way, the ideal is to reproduce this habitat as much as possible, thus giving well permeable soils, sunny positions, regular fertilization and prevention of any pests.

These plants have one of the widest ranges of shapes, colors and sizes. For example, you can find pompom flowers, single flattened ones, simple daisy-shaped, anemone-shaped or very double and full flowers.

Dahlias can be obtained both by seed and vegetatively. Both methods can be good, but for some species it will be good to use one procedure over the other.

FebruarySoil preparation
March AprilSowing, planting in a warm greenhouse
MayTransfer outdoors, planting, irrigation, fertilization
JuneTopping, unbuttoning, irrigation, fertilization
July AugustFlowering, irrigation, fertilization
SeptemberEnd of flowering, withering
OctoberPicking from the ground, division and drying of the roots
November-December-JanuaryStorage in a cool and dry place

Watering dahlias

As soon as they are planted, the dahlias do not usually need watering, as spring is usually quite rainy; in case of drought we moisten the soil to favor the development of the first shoots. Then we water with good regularity, avoiding to leave the substratum constantly humid, and therefore providing watering only when the soil is dry. From April to September we provide fertilizer for flowering plants, dissolved in the irrigation water, every 10-12 days. Watering is completely suspended from October until the following spring, even for specimens grown in pots.

Dahlias are fast growing vegetables and require large amounts of water. Keep in mind that it is important to find a balance, therefore always keeping the soil moist, but not soaked because the latter condition can favor root asphyxiation.

In general, we can say that during the summer and during flowering, in the absence of rain, it is necessary to intervene approximately 2 times a week.


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

Parasites and diseases

Dahlias are particularly afraid of tuber rot and also snails, which are greedy for foliage and tubers.

Meaning 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 the occasions when it is recommended are numerous. First, the dahlia is a perfect gift when you want to express gratitude to a person. For example, when you want to communicate to a person you love a feeling of closeness and esteem for some goal that that person has reached, the dahlia is an ideal flower. Another occasion in which you can give these flowers is to congratulate your collaborators for a job done in an optimal way or for a goal achieved.

Affection and admiration are therefore the two main feelings that are expressed when giving a Dahlia, a plant that before becoming an ornamental was also used in the kitchen. The tuber of the Dahlia was in fact cooked in some recipes of the early 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 (except sometimes having to wait a long time before seeing the flowering). However, it should be noted that the plants obtained will rarely have the same characteristics as the progenitors, in particular 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 done in a warm greenhouse or, later, in the open ground. In any case, a substrate with a medium mixture, but always well drained, must be used. The ideal is to buy it in bags or in any case make sure it is free of insects or other parasites.

The compost should be a mixture of peat and agricultural vermiculite. If we want to prepare it ourselves, we can mix 1/3 of silty and sandy 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 only with vermiculite. You will then have to vaporize 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 with direct light) until germination occurs. 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 eliminated and you will continue with light irrigations (without exaggerating, to avoid rot).

Direct sowing of dahlia

Since dahlia seeds are quite large, they can be planted directly, especially if the substrate is well worked. The best time is from mid-April to the end of May. Sowing can be precise (at a distance of at least 20 cm from each other, although a lot depends on the variety), or by spreading. In fact, they can be easily repacked because, if treated with care, they do not particularly suffer from transplantation.

Multiplication dahlia

The multiplication occurs by seed, towards the end of winter, or by division of the clusters of tubers, before offspring at home.

Vegetative propagation

Dahlias are characterized by storage organs located in the roots. These can take a fasciculated or tuberous form. Dividing these parts is a simple, fast and very common way of obtaining new seedlings ensuring, among other things, the maintenance of all the characteristics of the mother.

The only caution is to proceed by making sure that each fragment has at least one eye. To obtain good results, it is also extremely important to use well-sharpened and clean tools (possibly disinfected with a flame or with bleach).

The parts we obtain can be planted in the garden or initially kept in pots. In the latter case we use a very well drained compost and as sterile as possible to avoid the onset of rot where the cuts have been made (which is always good to disinfect with sulfur or other suitable products).

The portions of the root obtained by division can be re-planted usually in mid-May. A hole deep enough to contain the root will be dug, making sure that the top (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 sprout let's tuck it up by adding more earth up to the normal level. The distance between one plant and another is on average 60 cm, but a lot depends on the variety. We always refer to the indications of the nurseryman or the producer.

Propagation by cuttings

Another method is the cutting, which can be done during the growing season, usually in early summer. Portions of stems provided with at least two pairs of leaves and at least 20 cm long should be taken. It will be placed in a draining or sterile substrate (perlite or vermiculite). This must be kept humid and the temperature around 25 ° C. Rooting takes an average of three weeks, but a lot depends on the specific variety.

How to transplant well-formed seedlings (from seed, division or cutting) in the open ground

If we have proceeded with the sowing at home or in the greenhouse it will be necessary to later transfer the plants to the garden. Generally, the weather is not suitable until May, if we want to be sure to avoid too cold nights. The ideal is to extract all the ground bread without disturbing the roots too much. It is important that the collar maintains the same depth it had when it was in the container.

The supports

Dahlias often get very tall and consequently need supports.

Their large flowers and very moist stems are in fact easily broken by wind and rain. We then insert the canes very deeply and tie the plants without tightening too much, to avoid damaging them. The ideal is to use natural raffia or a soft plastic tube.

Planting dahlias

Dahlias are very nourishing plants. It is therefore good to commit from February working the soil very well up to at least 30 cm deep. 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 some 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 keep in mind that dahlias prefer a slightly acid substrate. So let's correct it accordingly with sulfur or lime, if necessary.

It should also be noted that, especially in the growth phase and that preceding winter rest, the dahlia needs good amounts of potassium: it is essential for good rooting and for a good accumulation of reserves before resting. If our soil were naturally devoid of it, integration with specific fertilizers will be necessary.

Dahlia care

Dahlias are quite susceptible to disease and insects and snail attacks. To obtain a good and above all long flowering you need to pay them constant attention.

It begins when the stems reach 5 to 15 cm in height. An insecticide (possibly pyrethrin) should be distributed every 15 days. We also always 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 they compete for nutrients, light and water and are often carriers of parasites. You can proceed with periodic hoeing or by preparing a thick mulch. Very useful for this type of plants is the one based on polyethylene sheets which, in addition to avoiding weeds, warms the soil avoiding excessive evaporation of water.

Topping and unbuttoning

When the individuals have reached about 35 cm in height they will emit an apical bud. It is imperative that both this and other neighbors are immediately removed. In this way the plant will grow more in width creating a dense and branched 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 larger central one, eliminating the lateral ones.

Bulbs of dahlias

The bulbs of dahlias 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 you can see in the image and it is understood that the dahlias, but as they grow, enlarge their bulbs increasing their cluster size.

Use as cut flowers

The peak of flowering occurs between July and August. In this period you can decide to cut the stems to use them in compositions. We always cut with very sharp scissors and at an angle. Then let's immediately place them 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 Dahlias are your favorite flowers or if you still 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 where Van Gogh was born but also for being one of the largest dahlia production centers in the world.

In fact, in the fields of this city over 600,000 bulbs are planted in a year in 31 hectares that are dedicated solely and exclusively to the cultivation of this species.

If you decide to visit the "city of the dahlia", however, you must do it absolutely the first week of September. In fact, in this period, every year since 1936, an incredible flower parade takes place that is able to amaze any person.

Giant floats halfway between engineering, art and decoration, invade the streets of the Dutch town giving a unique spectacle. All the floats are decorated according to a main theme but above all using Dahlia flowers. Just look at a few photos to be amazed.

Video: Посадка георгинов - 7 дач (October 2021).