Leeks are the mildest, most cold-hardy member of the allium family. They can overwinter in the ground in zones 5+ and provide harvests well into winter when other crops have finished.
Zone 6A has a moderate growing season. Most crops do well here with proper timing around frost dates.
Good companions: carrots, celery, onions, brassicas
Avoid planting near: legumes (beans, peas)
100-120 days from transplant; harvest when shank is 1 inch or more in diameter
USDA Hardiness Zone 6A has an average last spring frost around Apr 21 and first fall frost around Oct 15. All planting dates above are calculated from these frost dates. Your specific location may vary — check with your local extension office for the most accurate dates.