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 10B has a very long growing season with mild winters. Many crops can be grown nearly year-round with successive plantings.
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 10B has an average last spring frost around Jan 15 and first fall frost around Dec 31. 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.