The dahlia (Dahlia) is a genus of herbaceous and perennial flowering plants in the Asteraceae family. This genus is made up of 35 species endemic to Mexico, of which only four genera constitute the genetic base of commercial crops..
These plants are characterized by developing a fleshy root or fasciculate tuber that represents the main means of vegetative reproduction. The opposite, simple or pinnate leaves are triangular in shape with smooth and serrated margins and pale green in color..
The ligulate flowers are grouped in erect or inclined heads of various shades of red, purple, pink, orange or yellow. Flowering usually occurs during the summer or at the end of autumn, constituting the main commercial attraction of the crop.
At present, dahlias are cultivated worldwide, being their main ornamental use, as flowers in pots or cut flowers. However, recent studies have made it possible to determine certain medicinal properties for the treatment of diabetes and as a nutritional supplement.
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The species of the genus Dahlia They are herbaceous plants with bushy appearances, sometimes epiphytic or climbing, and with perennial or deciduous habits. Its size varies from creeping plants of 0.3-0.5 m, to erect plants 1.2-1.5 meters high with multiple branches.
The underground root that emerges from the neck of the plant is of the broadly fasciculated tuberous type. Indeed, the tuberous root of the dahlia lacks nodes or internodes, and constitutes a storage and reproduction structure.
The leaves, depending on each species, can be simple or compound, also in an opposite or whorled arrangement. Likewise, the entire or divided leaf blade is oval in shape with straight or serrated edges and a pale green color..
The flowers are arranged in inflorescences grouped in campanulate heads of variable size, shape and color depending on the species. Shapes vary from hemispherical, simple, or racemose, and predominant colors include white, red, pink, orange, or purplish.
The inflorescences have two types of flowers, the ligulates located on the outside, generally sterile and of a great variety of colors. As well as the central ones arranged on the disk or receptacle, tubular, hermaphroditic, fertile and colored yellow, orange, red or purple..
- Kingdom: Plantae
- Subkingdom: Tracheobionta
- Division: Magnoliophyta
- Class: Magnoliopsida
- Subclass: Asteridae
- Order: Asterales
- Family: Asteraceae
- Subfamily: Asteroideae
- Tribe: Coreopsideae
- Gender: Dahlia Cav. 1791
- Species: 30 species, 20,000 varieties
Pseudodendron section
- Dahlia campanulata
- D. imperialis
- D. tenuicaulis
Epiphytum section
- D. macdougallii
Entemophyllon Section
- D. congestifolia
- D. dissecta
- Dahlia foeniculifolia
- Dahlia linearis
- D. rupicola
- D. sublignosa
- Dahlia scapigeroid
Dahlia Section
- D. apiculata
- D. atropurpurea
- Dahlia australis
- Dahlia barkeriae
- D. brevis
- D. cardiophylla
- Dahlia coccinea
- Dahlia cuspidata
- D. excelsa
- D. hjertingii
- Dahlia merckii
- Dahlia mollis
- D. neglecta
- D. parvibracteata
- Dahlia pinnata
- Dahlia pteropoda
- D. rudis
- D. scapigera
- Dahlia sherffii
- Dahlia sorensenii
- D. spectabilis
- D. tenuis
- Dahlia tubulata
- Dahlia variabilis
The gender Dahlia It is native to the Mesoamerican high valleys of Mexico, El Salvador, Guatemala, Honduras, Nicaragua and Costa Rica. As well as some regions of South America and some northern states of Mexico where they were introduced as wild crops.
The great diversity of species of Dahlia comprises a wide altitudinal range, from 200-500 masl to 1,500-2,500 masl as the Dahlia australis. The genetic diversity of the crop adapts to frequently calcareous, stony, rocky, volcanic and even clayey soils.
This crop comes from and adapts to tropical and subtropical climates, but has become accustomed to various environmental conditions. In Europe they were introduced by the Spanish, being in Belgium the place where the first commercial crops were established.
Dahlia is an undemanding plant on soils, although it adapts to loamy, well-draining soils. In addition, a high content of organic matter and nutritional elements, as well as a pH range of 6-8.
The optimal climatic conditions for this crop should oscillate between 18-23 ºC of average temperature and 75-78% of relative humidity. Most varieties of dahlia are susceptible to low temperatures and occasional frosts.
This crop is generally managed under controlled irrigation, so high rainfall in the productive phase of the crop is favorable. Likewise, it requires natural or artificial protections against the wind, since it does not tolerate strong winds..
Dahlias are commercially grown in sunny areas, although they are well adapted to semi-shady conditions. However, full sun exposure should be avoided, as strong radiation tends to burn the leaves and tender shoots..
During the establishment of the crop, irrigation should be moderated to avoid damage due to waterlogging or incidence of root system diseases. In the growth and production phase it is necessary to increase the frequency of irrigation, also during dry periods and summer.
The dahlia is propagated by various methods of reproduction, through seeds, division of tubers, cuttings and even through crops in nitro.
Technique used for genetic improvement purposes, in order to obtain pure varieties and avoid crossing between cultivars. In fact, it is used in potted crops under a nursery, where rigorous control of edaphoclimatic conditions is maintained..
The ideal time to sow dahlias by seed is at the beginning of spring, on a substrate rich in organic matter mixed with sand. Maintaining an average temperature of 15-18 ºC, the seeds begin their germination from 15 days after sowing.
The plant requires 1-2 chimes during its development phase in order to select vigorous plants and favor their adaptation. Finally, a transplant is carried out to the final terrain, trying to maintain a spacing of 0.8 m between plants..
The division of tuberous roots or tubers is the most used propagation method to multiply dahlias due to its ease and high effectiveness. Indeed, the dahlia develops a series of tuberous roots that act as a storage structure that are used for its reproduction.
These tubers can be stored for a certain time under special conditions for use as a means of propagation. Indeed, the tubers are placed in germination trays with a fertile substrate, in conditions of humidity and warm temperature.
At the beginning of sprouting, the tubers are divided, trying to keep 2-3 vegetative buds for each fraction to guarantee grip. It is advisable to carry out this procedure during the spring and sow the fractionated tubers directly in the final field.
The technique consists of placing selected cuttings in cultivation under greenhouse conditions to promote the sprouting of vegetative buds. It is advisable to sow the tuber in a substrate of peat and sand, ensuring humidity and average temperature of 15-20 ºC.
The shoots emerge from the portion of the tuber that remains on the substrate. When these new seedlings reach a height of 5-10 cm they are separated from the mother plant keeping part of the tuber.
These cuttings are placed on growth trays with enriched peat, constant humidity and a temperature of 18ºC. After 15-20 days the cuttings open vigorously rooted to be transplanted to their final soil.
The propagation in vitro Dahlia is the best alternative since it guarantees clonal multiplication due to the genetic variability of the genus. This technique is carried out from selected meristematic tissues of healthy, vigorous and productive plants..
Sowing, either by division of tubers or cuttings, is carried out during the first month of spring. In commercial crops, different planting frames are managed, for large flower species 1 x 1 meters, and for small flowers 0.5 x 0.5 meters.
The various varieties of dahlia prefer non-calcareous soils, with pH adjustment to neutral, preferably fertilized with composted manure.
When preparing the soil, a fertilizer with a high content of phosphorus and potassium is recommended, as well as a maintenance fertilizer with nitrogen. Organic fertilizers or fertilizations with high nitrogen content can cause physiopathies at the foliage level..
Indeed, excess nitrogen weakens stems, promotes leaf production, and can damage flower buds. On the other hand, phosphorus and potassium make the stem stiff, intensify the color of the flower and ripen the tubers..
It is advisable to carry out regular and abundant waterings, trying to keep the substrate moist. However, the application of irrigation on the leaves and the waterlogging of the soil or substrate should be avoided in all development phases..
The practice of clamping or pinching is carried out on young seedlings when they are 15-20 cm high. Indeed, the clamping is carried out on the third pair of true leaves counted from the base of the stem.
This technique seeks to eliminate secondary shoots and flower buds located in the axils of the leaves, keeping only the main shoot. The objective of this practice is to achieve that the stem that supports the main flower reaches a length of better commercial value.
With the unbuttoning it is intended to obtain flowers of better size and quality of the cut. This technique seeks to guide and control flowering by suppressing flower buds located in the leaf axils..
This activity is carried out when the fabrics remain tender, before the buttons reach 5 cm in length. With this maintenance pruning, the production of a main flower with stems 60-70 cm in length is achieved..
The adults and nymphs suck the sap from the leaves, causing yellowing and general weakening of the plant. In addition, they secrete a molasses on which a fungal disease called bold develops..
Low incidence of the pest allows its biological control with Adalia bipunctata Y Aphidius colemani. For larger incidents, preventive control is carried out by applying a systemic insecticide.
It occurs in low humidity conditions and manifests as small yellowish spots, curling of the leaves and defoliation. In addition, the presence of cobwebs on the surface of the leaves is common..
The control is carried out through management increasing the humidity of the crop, or using the biological controller Phytoseiulus persimilis. In severe attacks, the application of sulfur-based chemicals is recommended..
Damages are caused by adults or larvae feeding on the sap of the leaves, causing yellowing and weakening of the plant. The control is carried out with systemic insecticides when observing the presence of adults on the crop.
The damage appears as small whitish spots with a leaden appearance surrounded by black specks on the leaf blade. Preventive control with anti-thrips traps or biological control with Orius or Amblyseius swirskii.
This type of pest is beetle larvae that settle in the soil causing damage to the root system. Preventive control is carried out with disinfection of the substrate, in severe attacks it is recommended to apply systemic insecticides.
Symptoms of the disease are rounded spots on the leaves that influence the commercial quality of the crop. The control is carried out in a preventive way, eliminating diseased plants, disinfection of the substrate or tools, and with expansion of the sowing density.
The main symptom is the change in color of the older leaves and the internal tissues turn brown. The general damage extends to the upper part of the plant and is favored by practices such as irrigation, handling and presence of weeds.
The control is preventive through the use of healthy plant material, elimination of diseased plants and reducing the frequency of irrigation. Chemical control is deficient, so preventive measures are adequate, including disinfection of work material.
Among the main bacteria that affect dahlia cultivation are the Erwinia chrysanthemi, Agrobacterium tumefaciens Y Corynebacterium fascians. The recommended control is through preventive measures such as disinfection of tools, elimination of diseased plants, sanitation pruning and weed control..
Cucumber mosaic virus (CMV) and dahlia mosaic virus (DMV) are the main viral problems of the crop. The symptoms vary from spots at the level of the veins, depigmentation of the leaves, to irregular growth of the leaves..
Prevention is accompanied by the control of pests such as aphids. In addition to the disinfection of work material, elimination of diseased plants and weed control.
Known as red dahlia or chalihuesca, it is an ornamental plant belonging to the compound family or Asteraceae. Species native to Guatemala and Mexico, it is one of the main ancestors of the current ornamental dahlias.
The so-called Catalina dahlia is located from central and southern Mexico to Colombia, being a herbaceous or shrubby species. The Dahlia imperialiss It is a perennial and tuberous plant that reaches high altitude, generally between 8-10 m in height..
Native plant of northeastern and central Mexico. It is a highly branched and compact plant, with divided leaves with numerous heads with ligulate lilac-whitish flowers..
Species distributed between Guatemala and Mexico. It is characterized by simple and divided leaves, with long petioles with fleshy bracts, ray purple or violet flowers with some yellow spots..
It is a hybrid herbaceous plant of certain Mexican species that reaches 0.70-1.50 meters in height and has a thick tuberous root. The current varieties are hybrids originating from Dahlia pinnata, D. coccinea Y D. purpurea.
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