Spinach Amaranthaceae, Spinacia
Place of origin: Southeast Asia, Iran～China North East Region
Optimal temperatures for germination 60—68℉ (15~20℃)
Optimal temperatures for plant growth 60-68℉ (15~20℃)
Characteristics Scientific name: Spinacia oleracea
Spinach suits cold climates and grows even at temperatures around 50℉ (10℃). Spinach that grows at lower temperatures for a short period of time will have thick leaves, will taste good, and will contain a high amount of vitamin C. When the temperature drops below 32℉ (0 ℃), spinach will stop growing. Spinach can endure low temperatures up to 14℉ (-10℃), but can still die if there is a rapid plummet in temperature instead of a slow decrease. However, spinach is vulnerable to high temperatures. When temperatures exceed 86°F (30 ℃), spinach will grow badly and can easily die.
Soak seeds in water and then drain. Soaking removes the growth inhibitor that the skin of spinach leaves, and then the seeds will germinate in a good condition. Spinach can have poor seed germination and can grow in irregular size and shapes during the early stages of growth because spinach has trouble breathing at high temperatures or when its thick leaves contain a lot of water. Spinach needs to be watered just after seeding, but after that, it doesn’t need much watering. Usually, spinach will gradually lose water. However, in some situations it is best to sow already germinated seeds.
Promoting Germination at Low-temperatures
Soak seeds in water heated to around 86℉ (30℃) for a few hours, then drain off the water, place the seeds in a cloth bag, and store in a warm place. When 20-30 percent of the seeds germinate, sow the seeds immediately. Give enough water to the ridges beforehand so that watering is not needed for a while after seeding. Cover the seeds with soil, and pat down the soil so that it is even. Then, cover the seeds with grass to prevent drying.
Promoting Germination During High-temperatures
Place the seeds in a cloth bag and soak the bag in water for a 24 hours. Drain the water and keep the seeds in a cool, shady place or in a refrigerator (around 40°F or 5℃ ). Stir the seeds from time to time while checking on their condition. When 20-30 percent of the seeds germinate, sow the seeds immediately. Give enough water to the ridges beforehand so that watering is not needed for a while after seeding. Cover the seeds with the soil, and pat down the soil so that it is even. Then, cover the seeds with grass to prevent drying.
Because soil dries out easily in spring, watering is needed. Even so, frequent watering after seeding causes germination failure, for the skin of the seed will contain too much water. Therefore, do not water too much. When four leaves appear after the cotyledon, bacteria wilt easily occurs, so don’t over water.
As the seedlings grow, thin them out. When leaves emerge after the cotyledon, thin out the seedlings that are growing densely. Ultimately, the space between seedlings should be between 2-3” (6-8 centimeters). Thin the plants as they grow and harvest the plants that are in dense clusters.
When seeding in autumn, harvest the plants as grow large. When seeding in spring, don’ t miss the harvesting time, as spinach easily bolts. It is good to sow seeds at different times and harvest all the plants that were sown at one time, which cuts down on labor. When the leaves reach a length of 9-10” (23-25 centimeters), harvest the plants.
Cultivating Seeds Sown in Spring
As plants grow when the daytime becomes long, bolting easily occurs. It is preferable to choose varieties that do not easily bolt. When temperatures exceed 77℉ (25 ℃) spinach will stop growing. Therefore, try to harvest spinach before temperatures get hot. When seeded in May, it takes 30-40 days until harvest. Spinach does not grow well in highly acidic soils, and its leaves will become yellow. Acidic soils do not suit spinach.