How to grow cornflower
The cornflower (Centaurea cyanus L.) is a herbaceous species of the Asteraceae family, with an almost annual cycle, varying in height from 20 to 90 centimeters, with erect stems, small elongated leaves and blue-toned flowers. It is used for ornamental purposes both in pots and in villas and gardens. Present in Italy also in the spontaneous state, in the warmer climates, it is available in different varieties but with very similar crop characteristics. We will therefore see how to grow cornflower and the most appropriate agronomic techniques. This plant grows well in temperate climates, with exposure to the sun but in conditions of heat not excessive and with non-arid, but well drained and soft soils, even if it is a plant that, if cured and irrigated, adapts well to colder climates and pedological conditions with more sandy soil. Flowering is spring and summer. It is advisable before the implant to make good amounts of organic matter (if it is also outdoors with mature manure).
For its cultivation it is advisable to program the water availability and the watering shifts; irregularities in water supplies (stagnant or prolonged aridity) compromise the growth of the plant and above all the flowering. In general it should be irrigated three to four times a week, with more frequent summer shifts.
The cultivation of cornflower is possible, as mentioned, both in pots and in the garden. For pot cultivation we recommend medium-sized planters while for the garden it is suggested to form small fragrant bushes.
In cultivation in pots (planters) you should take care to put on the bottom a bed of expanded clay or coarse gravel, to facilitate drainage, on which to place the soil composed of a mixture of 40% sand and 60% well-fertilized soil . In the garden it is more useful to use mature manure or compost, with a small monthly addition.
For the cornflower plant we recommend direct sowing to avoid subsequent transplants to which the plant does not respond well. For sowing you can also choose a certain scalability with periods ranging from the end of February, mid-March to late summer; this is because the cornflower is well suited to different climatic conditions and also to have longer flowering periods.
For the maintenance of planters or flowerbeds it is advisable to periodically eliminate the stems, the leaves or the dried flowers (also to prolong the flowering).
If the cycle of the plant is more than one year it is advisable in the winter (for the plants in the garden) a shelter from the cold obtained with a mulch of leaves or straw. Also from the point of view of resistance to insects or cryptogams, it is a very rustic plant provided that no nitrate or excessively nitrate fertilizers are used, especially in the garden, which tend to excessively vegetate the plant at the expense of less resistance and even less flowering.