The inflorescence of the sunflower is shaped like the disk of the sun, which is why many people call it a sunflower. In the early morning, it opens to the rising sun and follows its movement until sunset. When the sunflower comes to the end of its life, it stands quietly in one position, but its flower caps are always turned to the east. Because of this characteristic, the sunflower is a symbol of devotion among many peoples.
Today, sunflowers find their place firmly on garden plots, not only as food but also as ornamental crops. In addition, they are used in landscape decorations, hedges, individual plantings, and arrangements of flowers, and this article will show you how to growing sunflowers.
The sunflower belongs to the Asteraceae family, and the common name of the plant is Helianthus annuus, which is almost a direct translation of the words “sun” and “flower,” the Greek word for sunflower is “helios.” “It is native to the warm regions of North America, and its wild form occupies a wide area in grasslands, coniferous forests, and lowlands.
Of the 108 species of sunflower, more than 50 are grown in North and South America. The crop appeared in Europe in the 17th century. Gradually, sunflowers occupied vast areas of warm Eurasian regions, first as an ornamental crop and later as a technical and food crop. Today, varieties and hybrids have been developed that can be grown even in colder regions.
The annual sunflower is a single-stemmed plant up to 10-16foot (3-5 m) tall. The crop has a very interesting root system that can withstand the long dry periods of summer. Sunflower roots grow rapidly in the cotyledon stage, reaching lengths of 2-4inch (6-10 cm); by the 3-4 leaf stage, the roots elongate to 40inch (1 m). The root system is branched. The central taproot of adult plants grows to a depth of 10-13 feet (3-4 m) and is well resistant to soil drought. 2-3 orders of lateral roots depart from the central root. They are aligned parallel to the soil at 4-18inch (10-45cm) per level and extend from the central root to a distance of 80inch (2m). The lateral roots of sunflower form a dense network of rootlets that absorb water and nutrients. The growth of the root system stops at the inflorescence formation stage.
The leaves and stems of sunflowers are rough to the touch and densely covered with bristly hairs. The leaves are simple, large, petiolate, dark green, covering the stem up to the tip and ending in an inflorescence (a basket) composed of 2 types of flowers: ligulate and tubular.
The flowers of sunflowers are various shades of yellow. Varieties with tawny flowers are also common. The tubular, ovate flowers produce fruit after pollination. Sunflower is a cross-pollinated crop. Some cultivars may have several basket-shaped inflorescences that grow on pedicels that grow from the leaf axils.
The fruit of the sunflower is the seed. The seed is elongated, wedge-shaped, covered with a leathery pericarp, and contains 2 well-developed seedpods. It accumulates storage material in the form of oil and protein in the seedpods.
Sunflower is divided into 2 types according to size and weight.
- Oil sunflower, which is characterized by thin skin and black flesh, high oil content in seed balls (40-50% or more), and small seeds.
- The edible sunflower has a thicker and denser seed coat; it has a larger seed coat and a lower oil content (up to 25-30%).
The seeds are arranged in a circular shape. They vary in size from the edge of the pod to the center. The seeds are dormant for 1.5 to 2 months after harvest.
SUNFLOWER VARIETIES AND HYBRIDS SUITABLE FOR GROWING IN THE GARDEN
Sunflower varieties and hybrids are divided into early, medium, and late-maturing stages. Early and medium varieties are more practical for rural growth. In this case, the harvesting time allows you to prepare the plot for the next crop.
Sunflower seed varieties
Early sunflower varieties that can be recommended for planting are Skyscraper and American Giant Hybrid. They are characterized by a short vegetative period of 70 to 80 days and have a high oil content. In southern areas with a long warm period, they can be sown in two stages: in the spring in May and again by July with a good harvest. They are drought resistant and tolerate hot and dry summers well.
Other varieties are Russian Mammoth, Giant Sungold, Elf, Suntastic Yellow, Firecracker, Dwarf Incredible, Teddy Bear, Topolino, Little Becka, Italian White, Moulin Rouge, Strawberry Blonde, Earthwalker, etc.
It is believed that this variety is more resistant to spreading the traits of the parent. And this is the main mistake vegetable growers make with sunflowers. Sunflower varieties, through heterogeneous pollination, form genetically heterogeneous seed material, where the degradation process dominates. Thus, during the replication of sunflower varieties, only the first propagated seeds are ever obtained. All subsequent ones are significantly heterogeneous: different heights, size of the flower basket, prolongation of seed maturity, etc.
Unlike varieties, sunflower hybrids are highly genetically uniform and favor the simultaneous passage through developmental stages (seedling emergence, mass flowering, formation, crop maturity, etc.). As a result, hybrids are more resistant to stressful weather conditions, diseases, and pests, forming higher yields.
Breeders are currently concentrating their efforts on breeding hybrid sunflower varieties. We can recommend sunflower hybrids for successful cultivation in greenhouses in the South, the United States, and other European regions.
Tips for sunflower hybrids
- The earliest variety: ‘ProCut Orange Excel.’
- The best choice for resistance to downy mildew: ‘ProCut Orange DMR.’
- Most uniform in appearance and harvest date: ‘ProCut Horizon.’
- Best for when you want to ‘grow pale and fun.’ ‘ProCut White Lite’ & ‘ProCut White Nite’
- Best single stem sultry red color: ‘ProCut Red.’
- Most uniform in appearance and harvest date: ‘ProCut Horizon.’
- Popular for its upward-facing ‘lollipop’ appearance: ‘Vincent’s Choice.’
- Best for winter production in the south; tall and stately with a classically good appearance: ‘Full Sun Improved.’
- best for ‘3-D appearance’ at lower light intensities (early summer, late summer, and greenhouse conditions), drawing the eye from the creamy white lemon tips to the bright yellow petals and then to the mesmerizing dark discs: ‘Sunrich Limoncello Summer’
- Best for producing delicious edible seeds: ‘Royal Hybrid 1121.’
Other sunflower hybrids are as follows: Earthwalker, Giant Single, Moulin Rouge, Moulin Rouge, Bicentenary, Big Smile, Choco Sun, Indian Blanket, Kong, Pastiche, etc.
When buying varieties and hybrid seeds for propagation, be sure to choose zoned ones, which can greatly reduce the scale of crop losses caused by pests and diseases.
ENVIRONMENTAL REQUIREMENTS OF SUNFLOWER
Sunflower is a plant native to long heat periods and abundant sunshine, requiring heat, light, fertile soil, and moisture. The vegetative duration of sunflower is 80 to 140 days, depending on the variety. Therefore, sunflowers usually grow outdoors and produce good yields only if the climatic and agronomic conditions in a particular part of the world meet their requirements.
If the overall climate of an area is suitable for sunflower growth, but frosts of 21-25°F (-6 to -4°C) occur each spring, agricultural experts do not recommend growing this food crop, especially for mid-to late-maturing varieties. During the long growing period (100-140 days), the crop will remain incomplete and not mature.
Temperature requirements for sunflower
Sunflowers are best grown in a location that is not exposed to shade and is not exposed to the constant wind. In the shade, sunflowers become elongated and bend toward the sun, forming small inflorescence baskets and crushed sunflower seeds.
Sunflowers require 68-80°F (20-27°C) for normal growth and development. Sunflower seedlings are hardy and can tolerate air temperatures as low as 21-23°F (-6 to -5°C), but they need to heat the soil to 46-53°F (8-12°C) to germinate.
Sunflower requirements for lighting
Sunflowers are neutral to the length of sunlight, but they respond positively to daylight during flowering. If the light intensity is high during this period, sunflowers will enter the generative phase of development earlier; in cold foggy, and rainy weather, the process of entering the next stage is delayed. Harvest develops and matures at a later time. Therefore, sunflowers should be sown on well-lit plots, avoiding even temporary shade, and protected from the wind.
Water requirements of sunflower
Sunflower needs a lot of water to form its vegetation and to provide necessary nutrients for its reproductive organs. This is especially true during the early development of sunflowers when their roots are in the topsoil and are often affected by dry weather. At the same time, the sunflower is drought-resistant. As an adult, it is not afraid of heat because its strong root system is able to extract water from the lower soil layer of 10-13 feet (3-4 meters). Sunflower needs to be watered regularly until the flowering period, and then its usage is reduced. Watering is done according to the requirements of weather conditions (long hot periods, dry winds, etc.).
Soil requirements for sunflowers
The soil conditions for timely fertilization do not play a fundamental role in sunflowers. However, the crop prefers black soils, sandy loams, floodplains, and loesses. (Loesses are macroporous soils containing calcium carbonate and exhibit settling characteristics when soaked with water under load). Sunflower grows well on humus and deciduous soils. The optimum soil acidity is pH=6.5-7.0-7.2. They cannot grow in heavy clay, acidic, and saline soils.
SUNFLOWER SEED GROWING TECHNIQUES
When a sunflower is planted in a vegetable rotation, it must return to its previous location no sooner than 6-8 to 10 years after harvest. The longest rest period (up to 10 years) is required if there is an infestation in the vegetable garden. It is preferable to plant sunflowers in shallow-rooted predecessors so as not to dry out the deep soil, whose moisture is necessary for sunflowers.
Undesirable from this point of view are sunflower precursors of alfalfa, sugar beet, and perennial grasses. When selecting precursors, look for crops with common pests and diseases (soybeans, peas, canola, tomatoes, onions, and beans).
Sunflower’s best neighbors and predecessors are potatoes, sweet corn, and others that can be used for fall soil preparation for sunflower. Tall grasses planted o