Remove roots, outer leaves, and tops from leeks, leaving 1 1/2 to 2 inches of dark leaves. Slice leeks in half lengthwise; rinse with cold water.
Drain.
Remove dark leaves; chop dark leaves to measure 1 1/2 cups; set aside. Chop bulb ends to measure 2 cups; set aside.
Remove stalks from fennel bulb. Chop the stalks to measure 1 1/2 cups; set aside. Chop bulb to measure 2 cups; set aside.
Combine chopped dark leek leaves, chopped fennel stalks, 5 cups water, wine, and fennel seeds in a large Dutch oven; bring to a boil. Reduce heat; simmer 25 minutes. Strain leek mixture through a sieve over a bowl, reserving stock; discard solids.
While the vegetable mixture simmers, combine 8 cups water and lemon juice. Working with 1 artichoke at a time, cut off stem to within 1 inch of base; peel stem.
Remove bottom leaves and tough outer leaves, leaving tender heart and bottom.
Cut artichoke in half lengthwise.
Remove fuzzy thistle from bottom with a spoon.
Cut artichoke lengthwise into quarters; place in lemon water. Repeat procedure with remaining artichokes.
Drain artichokes; discard lemon water.
Heat oil in pan over medium heat.
Add chopped leek bulbs, salt, and pepper; saut 5 minutes.
Add garlic; saut 2 minutes. Stir in chopped fennel bulb, artichoke quarters, reserved stock, potato, chickpeas, tomatoes, and saffron; bring to a boil. Cover, reduce heat, and simmer 35 minutes or until vegetables are tender.