Detailed Guide to Corydalis Cultivation Techniques: Methods for Growing This Chinese Medicinal Herb

Seed Selection:

There are two types: large-leaf Corydalis and small-leaf Corydalis. Large-leaf Corydalis is suitable for close planting and gives high yields, while small-leaf Corydalis produces larger tubers of higher grade, but yields slightly less.

Site Selection and Land Preparation:

Corydalis roots grow shallowly and are concentrated within the top 5-20cm of topsoil, so the soil must be loose, with full sunlight, high and dry terrain and good drainage. Sandy loam and alluvial soil with loose topsoil rich in humus are best. Heavy clay or overly sandy land is not suitable for cultivation, and continuous cropping should be avoided. The soil pH can be neutral, slightly acidic or slightly alkaline. After harvesting the previous crop, plow and prepare the land promptly, plowing 20-25cm deep, and harrow finely to loosen the topsoil. Generally, beds are made 100-110cm wide with 40cm-wide furrows.

Propagation and Breeding

The planting period should suit the local climate conditions, and earlier is better than later. Early planting allows roots to develop before shoots emerge, which benefits plant growth and development. Late planting results in short, fine roots in fewer numbers, weaker seedling growth and reduced yields. Based on the climate conditions in Zhejiang, the planting time is generally from early September to mid-October. In production, newly formed tubers of the current year are mostly used, discarding the mother tubers, and tubers that are free of pests and diseases with a neat surface are used for propagation. Medium-sized tubers of 1.2-1.6cm are best for planting. Generally, drainage is carried out before the late-season rice harvest, and the land is prepared and sown promptly in mid-October. Strip sowing is mostly used, with furrows opened 18-22cm apart and 6-7cm deep, then two rows are placed alternately in the sowing furrow at a plant spacing of 8-10cm, with buds facing upward, covering with soil as you plant, to a soil depth of 6-8cm. A small amount of farmyard manure may also be applied in the furrow.

Field Management:

Corydalis has shallow roots and likes fertilizer, and its growing season is short, so applying enough base fertilizer is the key to increasing yields. Before land preparation, spread fully decomposed pig manure on the ground at about 45000kg per hectare, plow 15cm deep, and rake level. Rational fertilization is very important for increasing Corydalis yields. With sufficient base fertilizer applied, winter fertilizer should be applied heavily (from the Winter Solstice to Great Cold), and seedling fertilizer lightly. Winter fertilizer is applied in early to mid-December along with cultivation and weeding, mainly using farmyard manure. During the seedling stage there is much rain and high humidity, so pay attention to drainage and reducing humidity, ensuring no water remains in the furrows, otherwise root rot and reduced yields easily occur. Fertilization should specifically follow these points: water before freezing to protect the plants through winter, and also water before sprouting in spring. Corydalis likes fertilizer, so in addition to sufficient base fertilizer, it should also be topdressed promptly. When sprouts emerge at the Start of Spring, apply human and animal manure at 2250-4500kg per hectare, diluted with 3-5 times water. Or apply ammonium sulfate diluted in 300kg of water. Apply once more at flowering. Topdressing should be moderate; too much nitrogen fertilizer causes excessive vegetative growth, and high concentrations can also burn seedlings, so it is best to apply small amounts several times.

Corydalis likes moisture but fears waterlogging, so always keep the soil moist without standing water. Generally, after each topdressing, water appropriately so the fertilizer decomposes and is easy for the plants to absorb. Corydalis is a shallow-rooted crop, so deep cultivation and loosening of the soil are not suitable; only weeding is done. The number of weedings can depend on the weed situation, with the principle of always keeping the field free of weeds. Generally, weeds are pulled before topdressing to improve fertilizer efficiency.