How to Grow Spinach for High Yields? The Latest Cultivation Technique Guide

Spinach belongs to the goosefoot family (Chenopodiaceae) and is an annual or biennial herbaceous plant. Also known as red-root spinach and Persian spinach. It originated in the Persian region, present-day Iran, and was introduced to China around the Tang Dynasty. It has a long cultivation history and is widely grown throughout northern and southern China. It has wide adaptability, strong cold resistance, and good storage tolerance, with a long supply period, and it is easy to grow and quick to harvest, with relatively high yields. The product can be supplied in early spring and during the off-seasons of autumn and winter, making it one of the important vegetables in the three seasons of autumn, winter, and spring in the north. The whole spinach plant is emerald green, tender and delicious, and rich in nutrients, containing abundant vitamins and mineral elements. It is a vegetable with high nutritional value that is loved by the general public.

Biological Characteristics of Spinach

1. Botanical Characteristics

① Root. Spinach has a relatively deep and well-developed taproot. The taproot is slightly thick and somewhat swollen, red on the upper part, stores nutrients, and is sweet-tasting and edible. The main root mass is distributed within the 25-30cm plow layer. Lateral roots are not well-developed, making it unsuitable for transplanting.

② Stem. During vegetative growth it is a shortened stem, and during reproductive growth the flower stem elongates, reaching 66-100cm in height.

③ Flowers. Spinach flowers are unisexual, with a few being bisexual. It is dioecious, with a few being monoecious. Male flowers are in spike-like inflorescences, borne at the top of the flower stem or in leaf axils, without petals, with the calyx split into 4-5 lobes, and the number of stamens equal to that of the calyx. The anthers dehisce longitudinally, with abundant pollen that is yellow-green, and are wind-pollinated. Female flowers are clustered in leaf axils, without petals, with 1 pistil, 4-6 stigmas, and the calyx split into 2-4 lobes, enclosing the ovary, which has 1 chamber. Inside is 1 ovule. In prickly-seeded varieties, the calyx develops into horn-like protrusions. The “seed” used for sowing is actually the fruit. Female flowers are clustered in leaf axils, with 6-20 small flowers per leaf axil. They have no flower stalk, or have flower stalks of varying lengths.

④ Leaves. Before bolting, spinach leaves are clustered on the shortened stem as basal leaves. There are two leaf types: round-leaved and pointed-leaved. Round-leaved spinach has large, thick leaves with a smooth surface, ovate or spoon-shaped; pointed-leaved spinach has narrow, thin leaves, halberd-shaped or arrow-shaped, with acute or obtuse tips. Spinach leaves are dark green, tender in texture, and have slender petioles, and are the main edible part.

⑤ Fruit and seed. The spinach fruit is a utricle, irregularly round, containing 1 seed, wrapped in a hard leathery exocarp. It is divided into prickly and non-prickly types. The endocarp is suberized, with well-developed thick-walled cells, making it difficult for water and air to penetrate, so the seeds germinate slowly. The thousand-seed weight is 9.5-12.599, and under general storage conditions, seeds can be kept for 3-5 years, with seeds 1-2 years old having strong germinating power.

2. Requirements for Environmental Conditions

① Temperature. Spinach is the most cold-resistant vegetable among leafy green vegetables. South of the Yangtze River basin it can overwinter in the open field; in areas around -10 degrees, it can safely overwinter in the open field; in North China, Northeast China, and Northwest China, it can overwinter in the open field with windbreaks and ground cover. The cold resistance of spinach is closely related to plant growth and development and seedling age. Plants with 4-6 leaves can withstand short-term low temperatures of -30 degrees with their perennial roots, and at -40 degrees only the outer leaves freeze and turn yellow, while the root system and young buds are not damaged. If the seedling has only 1-2 leaves, or the seedling is too large, or the plant is about to bolt, it is prone to freezing damage and death during overwintering. Spinach has wide adaptability, with a suitable growth temperature of 15-30 degrees, and the optimum temperature is 15-20 degrees. Spinach seeds can germinate at 4 degrees, with a suitable temperature of 15-20 degrees, germinating in 4 days with a germination rate above 90%. As the temperature rises, the germination rate decreases.

② Light. Although spinach is a low-temperature long-day crop, flower bud differentiation is mainly affected by day length. Under long days and high temperatures it easily passes through the photoperiod stage, and under long days low temperatures promote flower bud differentiation. After flower bud differentiation, when the temperature rises and day length increases, bolting and flowering accelerate. Overwintering spinach, upon entering the following spring and summer, will rapidly bolt and flower.

③ Water. Under environmental conditions of 80%-90% air humidity and 70%-80% soil moisture, spinach grows most vigorously, with thick leaves, good quality, and high yield. Spinach requires a large amount of water during growth. Water shortage during the growing period slows growth, ages the leaf mesophyll, increases fiber, and makes it prone to downy mildew. Especially under high temperature, dryness, and long days, it promotes the development of floral organs and causes early bolting.

④ Soil and nutrition. Spinach has wide adaptability to soil, and it is best to plant it in loam that retains water and fertilizer, is moist (night-damp soil), fertile, and has a pH of 6-7.5, neutral or slightly alkaline. Acidic soil will poison spinach and is not suitable for cultivation. Spinach is a fast-growing leafy vegetable that requires more nitrogen fertilizer to promote leaf cluster growth, giving good quality and high yield. Nitrogen fertilizer should be increased on the basis of a complete nitrogen-phosphorus-potassium fertilizer.

3. Growth and Development

① Vegetative growth period. From spinach sowing and emergence to the full growth of all differentiated leaves and the beginning of inflorescence differentiation, from cotyledon expansion to the appearance of two true leaves, this stage grows slowly. After the two true leaves expand, the leaf number, leaf weight, and leaf area increase rapidly at the same time. The number of leaves at inflorescence differentiation varies with variety, sowing date, and climatic conditions, ranging from as few as 5-6 to as many as over 20.

② Reproductive growth period. From inflorescence differentiation to seed maturity, the early stage overlaps for a period with the vegetative growth period. Among external conditions, factors that can strengthen photosynthesis and nutrient accumulation generally promote female expression, and after bolting there are more lateral branches, more flowers, and fuller seeds.

Types and Varieties of Spinach

Based on the shape of spinach leaves and the presence or absence of prickles on the fruit, spinach can be divided into pointed-leaved (prickly) and round-leaved (non-prickly) types.

① Beijing Pointed-Leaf Spinach. A Beijing local variety. The leaves are arrow-shaped, with a pair of deeply lobed segments at the base, green, slightly thin in flesh, with less fiber and relatively good quality. The fruit is diamond-shaped and prickly. Cold-resistant and not heat-tolerant, with a yield of 1000-2500 kg per mu, suitable for overwintering after root stubble and for autumn cultivation.

② Japanese Large-Leaf Spinach. The leaves are elliptical to ovate, slightly pointed at the tip, with shallow notches at the base. The leaves are broad and thick, dark green. Strong heat tolerance, not cold-tolerant, suitable for summer and autumn cultivation. High yield and good quality.

③ Large Round-Leaf Spinach. Introduced from the United States, it belongs to the non-prickly type. The leaves are ovate to broadly triangular, the leaves are large and thick, the leaf surface is much wrinkled, and the color is dark green. The quality is sweet and tender, it bolts late in spring, has high yield and good quality, but is not cold-tolerant, with a single plant weight of 0.5 kg. The disadvantage is weak resistance to downy mildew and viral diseases. It is cultivated in Northeast China, North China, and Northwest China.