Spinach (Spinacia oleracea) is a vitamin- and mineral-rich vegetable that grows best in cool weather. The best fertilizer for spinach depends on what nutrients may be missing from the soil. Nitrogen can help a spinach plant grow faster and produce greener, more robust leaves. Fertilizer must be applied properly to avoid injuring the spinach plants.
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Best Spinach Fertilizer
The best way to determine what type of spinach fertilizer may be needed is to conduct a soil test. In very fertile soil, it may not be necessary to fertilize spinach. However, if you notice your spinach plants are growing slowly or that they are pale green in color, you can side-dress them with a fertilizer rich in nitrogen in order to speed up the process. This should be done about four weeks after planting if necessary.
To fertilize spinach, apply calcium nitrate at a rate of 1 pound per 100 square feet or 30 feet of row. You can also use 1/2 cup of a nitrogen-based fertilizer per 10 feet of row. Apply the fertilizer at least 4 inches away from the plants, as fertilizer can burn the plant roots. Water the soil immediately afterward so that the fertilizer will penetrate the soil.
Spinach Growing Requirements
In addition to proper feeding, spinach also requires a soil pH between 6.0 and 7.0. Anything more acidic than this can interfere with the growth of spinach. You should therefore have the soil in your garden tested before planting spinach and amend the soil with lime if necessary in order to achieve the appropriate pH. After they have begun to grow, spinach plants can also benefit from mulch that controls weeds that can compete with your plants for nutrients in the soil.
Spinach also requires plenty of moisture to produce the best-possible crop. Make sure your spinach plants are receiving at least an inch or two of water per week and that the soil remains consistently moist. You want to water spinach plants deeply to prevent the plants from developing a shallow root system.
It is best to water spinach plants in the morning so that the leaves have the opportunity to dry before nightfall. This is key to preventing foliar diseases that can affect the quality of your crop. Good drainage can also prevent many spinach diseases, including damping-off of seedlings.
Planting and Harvesting Spinach
Spinach is really easy to grow from seed. This vegetable should be planted in early spring in order for a crop to be ready before the heat of summer arrives, which can cause spinach plants to bolt, or send up flower stalks. This can diminish the quality of the leaves. If you plant spinach when soil temperatures have climbed past 85 degrees Fahrenheit, the seeds will not germinate. You can also plant spinach in the fall for a winter crop.
It can take anywhere from 37 to 45 days after planting for spinach to be ready to harvest depending on the variety you planted. You can harvest spinach once the leaves are big enough for cooking. As a rule of thumb, you should pick the outer leaves first.