PLANT OF THE WEEK
Dr. T. Ombrello - UCC Biology Department
What is a cone?
It is not a fruit and it is not a seed.
What most of us call a “pine cone” is really a cluster of highly
modified woody scales tightly packed together to protect the developing conifer
seeds inside. Conifers are the cone
bearing trees; and while most everyone knows that pines and spruces belong to
this group, the conifers are represented by over 550 species, including
hemlocks, firs, cedars, cypresses, yews, and even the common indoor Norfolk
Island Pine. The term conifer
is often used as a synonym for evergreen, and that really isn’t correct.
Some conifers are not evergreens (examples: Bald Cypress, Dawn Redwood, and Larch), and many evergreens
are not conifers (examples: Rhododendron
The Pitch Pine cone on the left was unheated.
The Pitch Pine cone on the right was heated to 130oF.
Every conifer species
has male and female cones. While
both the male and female cones start out small, the males do not grow to any
appreciable size, and are shed from the plant soon after releasing pollen.
They are rather inconspicuous and often go unnoticed.
The female cones grow large after pollination, maturing in a matter of
months for some species, and years for others.
Mature female cone size varies with species, from as small as ¼ inch to
over 2 feet in length.
Most conifer species
produce male and female cones on the same individual.
But some, like the yews and junipers, appear on separate plants.
Not all conifers make scaly cones. Yews
and junipers have a fleshy covering over each seed that resembles a small fruit
more than a cone.
While developing, the
scales of female cones are clasped together and usually held tight by resin.
When the seeds between the scales reach maturity, the cone responds by
changing color from green to brown, and separating its scales to expose the
seeds that will soon fall out. For
some species, the cones remain tightly closed until exposed to very warm
temperatures. New Jersey’s native
Pitch Pine, for example, will remain closed on the tree for years until exposed
to temperatures over 130oF. The
strategy here is that the tree will not release seeds until after a forest fire
has burned the twig and leaf debris from the forest floor, making the site
suitable for seedling germination and growth.
Conifers have two basic
means by which their seeds are dispersed; wind
or animals. Wind dispersed seeds are usually small, with a prominent wing
that allows the seed to be carried far from the parent plant by a breeze.
Seeds that rely on animals for dispersal are larger and non-winged.
They provide a nutritional reward for the animals, and those not consumed
immediately are usually carried some distance from the parent plant and hidden.
If not recovered, they germinate and grow.
Conifer cones and their
seeds have been used for a variety of purposes.
Besides the obvious use of cones for decorations, some seeds, like those
of pinyon pines, are used in prepared foods and baking.
The seeds of junipers provide the distinctive taste of gin.
The conifers represent a very successful part of the plant world. They enjoy a worldwide distribution, and have been around for the past 200 million years, producing their unique cones as their means of reproduction.