QUESTION: How do you fertilize spinach? Can you suggest an organic fertilizer? -Frank D.
ANSWER: Prior to planting spinach, amend the soil by working in a combination of compost and a balanced fertilizer. Amend the soil just a few days before planting so that the fertilizer has a chance to break down some.
Once established, a balanced fertilizer will work fine for spinach, but something with a bit more nitrogen might work even better. Something like 10-10-10 will get the job done, but a 15-10-10 is preferred. Use a granular fertilizer before planting, then switch to a water-soluble fertilizer once the plants are established. We recommend this switch because it makes it easier to feed the spinach plants without disrupting their shallow root systems using a water-soluble feed. Feed with the water-soluble fertilizer every two to three weeks or so during the growing season.
If you prefer to use a granular fertilizer during the growing season, use it as a side dressing along the edge of the rows and apply it once per month. Take care not to let the granules come in direct contact with the plants, as it will burn them. Water immediately after applying granular fertilizer.
For organic farmers, use fish emulsion or well-rotted manure to amend the soil before planting. Side dress with any organic fertilizer that is rich in nitrogen during the growing season. Plant and manure-based composts also work well for organic feeding and can be applied once or twice per growing season. Any water soluble balanced or nitrogen-rich organic fertilizer will work just fine.