Dill (Anethum graveolens L.) is an annual plant belonging to the Celeriaceae family. It is an early-maturing, cold-resistant, light-demanding plant, which is undemanding in terms of growing conditions but sensitive to waterlogging. The plant develops a rosette of leaves highly dissected into filamentous (thread-like) parts. In due course, a branching tubular stem develops, followed by inflorescences with seeds. All plant parts, especially seeds, contain essential oil.
Dill originated in the Mediterranean coastal area of Western Asia. In ancient times, it was used as an ornamental crop and mental activity stimulating effect was attributed to its flavor. The erudite competition winners were crowned with a dill wreath.
The seeds germinate at +3°C, and the young plants are capable of withstanding frosts of down to 6°C below zero. The optimum growth temperature is +15-22°C. Initially, plants develop leaves on a shortened shoot then, within 20-30 days of seedling emergence, internodes elongate and inflorescences enveloped in a pellicular axil are formed. This is the economic maturity stage. The dill leaves contain vitamins C, A, B2, B6, P, and PP, protein and mineral salts of calcium. At this stage, the most dramatic accumulation of green material rich in aromatic and other substances occurs. Owing to the short period of crop formation, dill greens can be grown both as a preceding crop and as a postharvest crop.
Growing tips
Dill is grown on structured, light, non-waterlogged soils. The preceding crops normally are row crops fertilized with organic and inorganic (mineral) fertilizers. Phosphate-potassium fertilizers (P2O5 80, K2O 60) are applied at autumn plowing and nitrogenous ones (N 120) at spring cultivation. It is good practice to prepare the soil in autumn and to sow immediately after harrowing in early spring – March-April. Where cultivated for greens, solid planting with grain seeders is used with a seeding rate of 20-25 kg/ha (20-25 g per 10 m2). The seeding depth is 1,5-2,0 cm and rolling should be done immediately after sowing without fail. The dill seeds have a high water absorbing capacity and, therefore, should be invariably placed into wet soil at sowing.
For extra early production of dill greens, underwinter or winter sowings are practiced. Underwinter sowings are normally performed with the onset of settled frost weather conditions in order to avoid premature germination. The soil is prepared in a usual way, except that the seeding rate is increased by 20-25%. The depth of sowing is 3-4 cm. Winter sowings normally take place after the snow or ice has melted away, the seeding rate being the same as with underwinter sowings. The thawing water from defrosting soil draws in the seeds into the soil. With both sowing times, the seedbed should be covered with a mulch of some sort (a thin layer of dry manure, peat or chopped straw). With these methods of growing, seedling emergence occurs 5 to 10 days earlier than with spring sowing and the crop is ready for harvesting in May. Setting up plastic covers allows the harvest time to be hastened.
The plants should be irrigated every three days with a water application rate of 5 l/m2. Where nitrogenous fertilizers were not applied in early spring, they are given as supplementary fertilizing throughout the growing season or as fertigation (a combination of irrigation and fertilization) at each water application under drip irrigation.
The dill greens can be harvested starting, approximately, in mid-May or late May. The harvesting is begun after the dew on the plants dries up. The plants are uprooted or cut just above the soil surface, bunched, closely packed into boxes/crates and promptly sold. The harvested dill plants cold-stored at +1-5°C can keep for 4 to 5 days.
For extended harvest of dill greens, a continuous string of sowings and harvestings is arranged from March till August at 10 to 20-day intervals. The highest crop yield is achieved with spring sowings.