Cultivating sunflowers can bring a much cheerier aspect to our vegetable garden or backyard. Obviously, cultivation for decorative purposes differs from commercial purposes. Sunflower cultivation is widespread worldwide, and the production of its sunflower seed oil needs no introduction. However, it’s evident that in these cases, it is practiced on very large surfaces. This plant, of South American origin, found its initial diffusion in Europe starting from the 1500s as an ornamental crop. Here, we want to focus on this perspective: a stunning flower with a spring-summer cycle that adds color to our land. Let’s see the right period for sowing, the necessary care for cultivation, and the possible uses in the vegetable garden and backyard.
But before we start with cultivation, let’s explore the botanical characteristics of the plant.
Botanical characteristics of sunflowers
The sunflower, scientifically known as Helianthus annuus, is a plant with an annual cycle. It belongs to the family Asteraceae (or Compositae), just like the dandelion.
The word Helianthus comes from the combination of two Greek words, helios = sun and anthos = flower.
The name clearly expresses the plant’s tendency to follow the sun’s movement with its large flower. In plant physiology, this behavior is known as heliotropism. Even in Italian, its common name clearly refers to this characteristic of the plant.
The sunflower is a plant characterized by significant development. In its natural habitat, it can reach up to 4 meters in height. However, in our climate, cultivated species for ornamental purposes usually reach up to 2 meters.
The stem of the plant is erect, cylindrical in shape, very robust, with a rough and bristly surface.
The roots of this flower are of the fibrous type and well-developed. They can go deep into the ground, especially in the first 40-50 cm, although they can reach up to 2 meters. This extensive root system allows the plant to find water in depth and, therefore, withstand water stresses.
The most salient characteristic of cultivating sunflowers is, of course, the large terminal inflorescence called calathid. This is composed of a flat-shaped disc receptacle, surrounded by a double or multiple series of bracts.
The calathid has a diameter ranging from 15 to 50 cm and is formed inside by hundreds of small flowers.
Depending on the variety, it can be single at the apex or multiple, with smaller heads in the lower branches.
In reality, the calathid is composed of two types of flowers, namely ligulate and tubular flowers. The first ones are the outer, asexual type. They are arranged in a corolla on one or two rows and consist of a large yellow ligule.
The others, the tubular flowers, are those of the inner disc. They are hermaphroditic, small in size, and less showy. They consist of an inferior ovary and a tubular-shaped perianth, with colors ranging from yellow to reddish.
The heliotropism of this flower works as follows: at sunrise, the calathids are clearly turned to the east, while at sunset, they face west. This natural mechanism stops when the calathids reach full maturity and begin seed formation. At that point, petals and corolla always face north/northeast.
In sunflower cultivation, pollination of the flowers is cross-pollination, i.e., heterogamous.
In essence, pollination occurs thanks to the action of bees and other pollinating insects such as bumblebees. Technically, this process is called entomophily.
Bees and other insects are highly attracted to the bright colors of the petals and the availability of pollen. Even a few plants in the home garden are, therefore, a precious resource for our bee friends. It is essential, of course, for this purpose, that there is no chemical contamination in our vegetable garden or backyard.
The fruit of the sunflower consists of a large achene with a particularly elongated shape. It consists of a hard and fibrous pericarp that adheres to the seed, with colors ranging from white to black to striped. The actual seed, however, represents 75% of the achene. It is formed by a seed coat, the embryo, and two cotyledons containing fats and proteins. This is where the oil is extracted from.
During seed formation, the calathid bends due to increased weight. At full maturity, it faces downwards.
If we decide to cultivate Helianthus annuus, we must think about choosing the best variety that suits our needs. The main varietal differentiation of seeds is based on the plant’s biological cycle, which varies on average from 110 to 140 days.
Most sunflower seeds available on the market are hybrids, divided into three macro classes according to their early, medium, or late cycle. The best yield in terms of seeds, and therefore fatty acids, comes from seeds with a medium-late cycle.
How to cultivate sunflowers
Soil and sowing period requirements
Cultivating sunflowers is a practice that typically follows a spring-summer crop cycle. This flower prefers a temperate climate with sufficiently high temperatures during the summer.
In general, the plant adapts well to the climate of our territory, as it is very hardy. The key is to identify the right sowing period, which is usually towards the end of March in southern regions and April in central and northern regions. It’s important to avoid the risk of frost, which can compromise seed germination and early vegetative growth of the plant.
Preparing the soil
The ideal soil for cultivating sunflowers should be well-draining. It should also be worked deeply to allow the root system to surpass the surface layers. In large extensions, the soil is usually plowed and refined with a subsoiler. However, for a domestic cultivation with only a few plants, these operations are not necessary. In this case, a good digging as normally done for vegetables is sufficient.
The seeds of this flower can be directly buried in the soil, making small holes. The depth of burial should be proportional to the size of the seed. In the case of sunflower cultivation, the seed should be inserted into the soil at a depth of about 3-4 cm.
The plants should then be spaced about 40 cm apart, while the distance between rows should be approximately 60-70 cm.
These spacings will allow all the plants to develop harmoniously.
This plant benefits from the presence of decomposed organic matter in the soil. Therefore, if we intend to cultivate sunflowers, it is good to fertilize using very mature animal manure or, alternatively, domestic compost.
Fertilization should be done a little before sowing, so it is well integrated into the soil.
The main needs of sunflowers are irrigation and weed control.
In terms of water requirements, there are no major problems. The root system goes deep into the ground, so the plant can find water on its own. However, from the initial phase until flowering, it is essential to ensure that the soil is always moist. Therefore, supplementary irrigation may be necessary. When the plant is mature, water needs decrease gradually.
Regarding weed control, this beautiful colored flower is affected by weed competition, especially in the initial phase. Later on, the cultivar takes over significantly.
To avoid hoeing operations, natural mulching can be used. This will also help to keep the soil more moist. With this organic agronomic technique, using straw, we can have significant aesthetic benefits as well.
Harvesting sunflower seeds
From a food perspective, the most valuable part of the plant is the sunflower seeds. They reach full maturity when the achenes easily detach from the calathid. To understand when it’s the right time to harvest, simply observe the calathid itself and the leaves, which become dry. The stem and stalks, on the other hand, start to turn dark.
Cultivating this plant in our latitudes means harvesting from late August to the end of September, depending on the degree of maturity reached and the plant’s cycle.
On an industrial agriculture scale, harvesting is done with specific combine harvesters appropriately adapted. On a domestic level, we can easily do it by hand with threshing on the threshing floor.
The benefits of sunflowers in the vegetable garden and backyard
The first advantage of cultivating sunflowers at the domestic level is the aesthetic factor. Observing a plant in full bloom up close is a fascinating sight. Country life should not only be about production but also about enjoying the peace that nature with its beauties can offer.
Another useful function is the natural attraction that this flower generates for bees and other pollinators. We know that the presence of these beneficial insects is crucial for the harmony of the entire ecosystem. And this, in turn, is essential for the health of our plants.
In addition to this, the flowering can be used as a “spy plant” for harmful garden insects. For example, the tomato leafminer is highly attracted to the flower’s yellow color and visits it frequently. The presence of the pest on the flower will allow us to intervene in time (perhaps with sexual confusion traps or other organic remedies) to save our vegetables.
In this regard, we recommend placing the flowers on the outer edges of the field, both to avoid disturbing other crops and to create a sort of external protective barrier.
Nutritional properties of sunflower seeds
Sunflower seeds have excellent nutritional properties. They have a high content of essential fatty acids, such as folic acid, useful during pregnancy, and linoleic acid, a substance used by our bodies to produce omega-3, which are useful for protecting against cardiovascular diseases.
They also contain B-group vitamins and vitamin E, which have antioxidant functions. Finally, they are very rich in minerals such as iron, phosphorus, zinc, magnesium, and potassium.
In industrial agriculture, sunflower seeds are mainly used for the production of sunflower seed oil. On a domestic level, we can use the seeds harvested from our organic plants as they are. In the kitchen, if we lightly salt and toast them, we can use them as a healthy and tasty snack or appetizer. We can mix them with almonds and pine nuts to make homemade pesto.
But there are also many other recipes to explore and get creative with.
Naturally, if you use seeds from your organic plants, you won’t have any issues. However, if you buy seeds for planting, make sure they come from organic sources. You can find a product with excellent quality standards here.
- University of Virginia – U.Va. Undergraduate Researcher Studies Sunflowers’ Power to Clean Up Soil – Research on sunflowers’ ability to absorb heavy metals and radiation from the soil, with potential applications in environmental cleanup.
- University of California, Davis – Why Sunflowers Face East – Discovery that sunflowers face the rising sun to attract more bees and reproduce more efficiently, leading to larger and heavier seeds.