On Food and Cooking

the cook. Stems and stalks support other plant
parts and conduct essential nutrients to and
from them, so they consist in large part of
fibrous vascular tissue and special stiffening
fibers — for example, the ridges along the
outer edge of celery and cardoons — that are
from 2 to 10 times tougher than the vascular
fibers themselves. These fibrous materials
become increasingly reinforced with insoluble
cellulose as the stem or stalk matures.
Sometimes there’s nothing to do except to
strip away the fibers, or cut the vegetable into
thin pieces to minimize their fibrousness, or
puree them and strain off the fibers. The keys
to tender celery, cardoons, and rhubarb are on
the farm rather than in the kitchen: choosing
the right variety, providing plenty of water so
that the stalks can support themselves with
turgor pressure (p. 264), and providing
mechanical support by hilling with soil or
tying the stalks together, so that mechanical
stress doesn’t induce fiber growth.