Lemon Cream Brussels Sprouts

4 ribs of celery, cut diagonally into 1/3-inch slices
2 tablespoons unsalted butter
1/4 teaspoon celery seeds
3 tablespoons all-purpose flour
1 cup milk
1 teaspoon freshly grated lemon zest
2 teaspoons fresh lemon juice
1 1/2 pounds Brussels sprouts, trimmed, blanched for 12 minutes in boiling salted water, or until they are tender, and drained, or two 10-ounce packages frozen, thawed

In a heavy saucepan cook the celery in the butter over moderately low heat, stirring, for 3 minutes, or until it begins to soften. Stir in the celery seeds and the flour and cook the mixture, stirring, for 3 minutes. Add the milk in a stream, whisking, and salt and pepper to taste and simmer the sauce, stirring, until it is smooth and thickened. Stir in the zest, the lemon juice, and the Brussels sprouts and simmer the mixture, stirring occasionally, until the Brussels sprouts are heated through. Transfer the creamed Brussels sprouts to a heated serving dish.  Serves 8.