Cones

Did you know that pine cones are actually modified branches and leaves? It's true!

Conifers produce seeds but not flowers. This makes them gymnosperms. Instead of flowers, conifers produce cones. Botanically known as strobili, cones are the reproductive organs of conifers.

Cone gender

There are male cones and female cones. Male cones, called microstrobilus or pollen cones, produce pollen and look very little like the cones we imagine. Male cones are more herbaceous than female cones, being modified leaves, and they look very similar to one another across species. Female cones are the familiar woody structures that produce and contain seeds. Female cones, also known as seed cones, ovulate cones, and megastrobili, are structurally unique to each species and helpful when it comes to identification. Female cones are modified branchlets.

Mature female Coulter pine cone (Didier Descouens) CC BY-SA 4.0

​Cone anatomy

​Female cones are covered with plates called scales. Female cones start out as a central stem covered with bracts. Bracts are modified leaves or scales with a small flower or flower clusters  in its axil. The bright red “petals” of poinsettia are not actually flowers. They are bracts. In some cases, the bracts harden and fuse to the woody seed scales.

Female cone anatomy (Nefronus) CC BY-SA 4.0

Male cones appear in clusters and are much smaller than female cones. They contain pollen sacs and generally start growing on the end of the previous year’s branches, usually lower in the tree canopy, below female cones. This prevents self-pollination.

​Cone and seed development

While male cones usually only last one year, it can take 3 or more years for a female cone to fully develop. Once a female cone is receptive and pollination has occurred, it can take up to a year for fertilization to be complete. As seeds develop, some cones will slowly begin to open, while other species need fire to trigger opening. Stone pine seeds, while delicious, require a lot of hard work to separate them from their cones.

Some conifer seeds have a wing that allows them to be carried on the wind, while other species rely on animals, such as squirrels, and birds help them disperse. Stone pine seeds, while delicious, require a lot of hard work to separate them from their cones.

Immature male cones of pine (Menchi) CC BY-SA 3.0

Types of cones

The cones of holiday decoration fame are only one of many different types of cones. The scales can be arranged in one of two ways: imbricate or peltate. Imbricate scales overlap much like roof tiles and are attached along a common axis. Peltate scales do not overlap and are attached from a central point, more like an umbrella. Some cones look more like berries than cones.

     Araucariaceae (monkey-puzzle tree, kauri, and the nearly extinct Wollemia tree) - fused scales create a spherical cone; imbricate

Monkey-puzzle tree with seed cones (MPF) CC BY-SA 3.0

    Cupressaceae (arborvitae, cypress, juniper, redwood, sequoia) - bracts and seed scales are fused; peltate

Nootka cypress (Walter Siegmund) CC BY-SA 3.0

Juniper cones (MPF) CC BY 2.5

    Pinaceae (cedar, fir, larch, pine, spruce) - archetypical cone; imbricate
 
​  Podocarpaceae (Prince Albert’s yew, Matai) - many of the scales are fused into a brightly colored, often edible aril; imbricate

Yew cone (Didier Descouens) CC BY-SA 4.0

Podocarpus cone (Alpsdake) CC BY-SA 4.0

   Sciadopityaceae (Japanese umbrella pine) - imbricate
​
   Taxaceae (yew) and Cephalotaxaceae (plum yews) - female cones have only one scale, with a single poisonous ovule; the surrounding fruit is sweet but the seed is deadly

While not conifers, cycads and welwitschia, or tree tumbo, also produce cones. Tree tumbo plants are considered living fossils and are unique in that female plants produce female cones and male plants produce male cones.

How many cone-producing plants do you have?