Cook these vegetables just before serving.
Fill two large pots with water. To one pot add beets and salt; to the other pot add potatoes, carrots, fennel, and salt, and bring both pots to a boil. Reduce to medium heat, and cook until vegetables are just tender, 20 to 25 minutes for the beets, and about 10 minutes for the potatoes, carrots, and fennel. Drain beets separately; when cool enough to handle, peel. Cover vegetables; keep warm.