(its saturation point). The slow-growing leaves of this species have very low nitrogen
content, and their growth increases only slightly when supplied with extra nutrients.
Like many other shade-tolerant plants, it has a single layer of leaves with little
overlap. The shadier the habitat, the more horizontal the leaves; being flat on the
ground also provides a bit of warmth in winter. The dark-green, opposite leaves
are nicely arranged – each one is just a half-inch in diameter, and each one has a
pale yellow stripe right down the middle.
Wintergreen, Gaultheria procumbens
Year-round, a crushed wintergreen leaf emits the pleasant smell of oil of
wintergreen – a sweet, clean, minty scent – although this species is in the
heath (Ericaceace) family, not the mint family. The leaves used to be a common
source of methyl salicylate, a medicinal oil that eases aches and pains and,
according to some people, cures many other ailments as well. Now, methyl
salicylate is more often synthesized. The compound has also been used for its
insecticidal properties yet, curiously, methyl salicylate attracts parasitoid wasps.
The stiff, shiny leaves of wintergreen are common in the shady understory of deciduous and
mixedwood forests and are particularly pretty in winter, when they often turn red. The anthocyanin
pigments that cause this color change may protect the leaves from excessive sunlight, but why the
winter leaves of some plants turn red and others don’t remains a puzzle. An inch or so long, the oval
leaves have prominent midribs and nearly smooth edges. Most of wintergreen’s growth is in spring
and fall. Like many small evergreen herbs, it is more common on north-facing slopes, where winter
sun is less intense and where drought is not so likely to be a problem in summer. It’s most often
found in somewhat acidic soils.
At four to six inches high, wintergreen is a bit more upright than partridgeberry, but it
too arranges its leaves in more or less a single layer, a bit like a miniature umbrella. It spreads along
the ground by way of well-rooted rhizomes, just an inch or so deep.
The white, bell-shaped flowers are similar to those of blueberries, which are in the same family. The
flowers are pollinated by insects, and when the red berries mature in the fall, they, too, smell and taste
like wintergreen. Chipmunks eat the fruits before turning in for the winter, and turkeys and red foxes
do the same until snow covers the ground. Deer and bears eat the leaves once in a while.
Christmas Fern, Polystichum acrostichoides
This fern, together with evergreen wood fern, accounts for most of the greenness of the forest
floor in the winter deciduous forest. It’s abundant, and unlike many other plants that are
green in winter, Christmas fern manages to get a good foothold on nutrient-rich sites,
especially if they face to the north.
The fronds of this robust fern grow to almost two feet, are leathery and dark green, and
have scaly stalks. Many ferns have their sori, or fruiting bodies, discretely positioned on
the undersides of the pinnae, but Christmas fern’s fruits are packed in at the top third
of the fertile fronds, so packed that the pinnae that bear them are constricted and
unhappy looking. The lustrous sterile fronds, on the other hand, are lovely. All of the
pinnae, sterile or fertile, are plain, without the feathery, much-divided patterns of
many other ferns, and each one has an upward-facing lobe at the base, suggesting to
some the heel of a stocking – maybe even a Christmas stocking.
Like other wintergreens, Christmas ferns have a sophisticated light-management
strategy. Especially in spring but to some extent in summer, the fronds are erect.
Direct sunlight, often in the form of sunflecks, is a bit too intense for their shade-adapted leaves, so they crowd together to avoid it. After the first frost, however, the
fronds flop to the ground, maximizing the lower light input. Plus, these prostrate
leaves, being on the ground, are up to 10 degrees warmer, which considerably
increases the rate of photosynthesis – a rate that is governed to a large extent
Deer do not like Christmas fern, and the increase in deer numbers over recent
years may be to its advantage, as deer prefer other understory plants.