Answer: It may be a lack of nitrogen fertilizer or too short a growing season, says Roy Ellerbrock, onion expert at Cornell University in Ithaca. Leeks are fairly heavy feeders of nitrogen and will grow thicker if they have a good supply of nitrogen through the growing season. Start with a well-drained soil amended with a two-inch layer of composted manure the previous fall. I'd suggest side-dressing each plant with one small handful of cottonseed meal four weeks after transplanting and again one month later, advises Ellerbrock. Leeks also need a long growing season to develop their normal 11/2- to 2-inch-diameter stem. You'll need to start seeds indoors under lights in mid-February and transplant them into the garden at the end of April in your area. To produce the best leek crop, space transplants at least five inches apart and keep them well watered and weed-free throughout the growing season. Varieties that grow well in New York are King Richard and American Flag, notes Ellerbrock.
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