Operation Terror by Murray Leinster

When darkness fell, Lockley and Jill were many miles away from the clearing where he had made the S. O. S. They were under a dense screen of leaves from a monster tree whose roots rose above ground at the foot of its enormous trunk. They formed a shelter of sorts against observation from a distance. Lockley had spotted a fallen tree far gone with wood-rot. He broke pieces of the punky stuff with his fingers. Then he realized that without a pot the bracken shoots he'd gathered could not be cooked. They had to be boiled or not cooked at all.

"We'll call it a salad," he told Jill, "minus vinegar and oil and garlic, and eat what we can."