PLANT OF THE WEEK

Dr. T. Ombrello - UCC Biology Department

CONIFER CONES

 

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 and Holly).  

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.