A coniferous plant produces one or more seeds in a cone structure. Cones come in many forms, from the soft, red berry-like structure of the yew, which produces only one seed, to the hard scaly spiral structure found on pines, which produces many seeds. As a group, pine trees produce similar cones, yet there is enough difference between species to identify the type of tree by the cone.
Male and Female Cones
Pine trees (genus Pineceae) are almost exclusively monoecious, which means that they have male and female cones growing on the same tree. The male cones are soft worm-like structures that produce a very large amount of pollen in the spring. What most call a pine cone is really the female structure, which is hard and scaly, and each scale is arranged in a spiral manner. Most pines are not self-fertilizing, which means the pollen from one tree needs to find a female cone on a different tree for fertilization to occur.
Seeds Form on Female Cones
Each scale on an ovulate cone (female cone) produces two ovules, which usually are fertilized with a pollen grain that comes from the same type of tree, but not the same individual plant. The pollen enters the ovule from an opening at the top called a micropyle. Each ovule is covered by a woody bract or scale. This scale is for protection and not reproduction. Once the cone is fertilized, it usually takes about two years for the cone to reach maturity.
Pine seeds are generally released from the cone in the second autumn after fertilization. Some cones require fire to release the seed, but many pine cones release the winged seeds to the wind currents. At other times animals may break apart a cone and release the seeds or consume part of the cone and deposit seeds later through the digestive tract. Other cones may fall to the ground and then be picked apart by animals.
Most pine seeds are winged, with the seed located at one end of a long flat piece of light woody material. Each bract can produce two seeds, which can travel a long way away from the parent tree if they become airborne. When still attached to the bract, winged pine seeds slightly resemble a very small set of hoof prints. Once separated from the cone, pine seeds are difficult to spot.
If a pine seed finds the right micro-climate, it will eventually sprout and a pine seedling will start to grow. However, pine seeds are usually released in a dormant state, which is most often broken by cold stratification. As a result, a pine seed will not sprout until the following spring when warm weather and some spring moisture are present. Since pine seeds are produced in abundant numbers, and only a small percentage needs to be successful in establishing new seedlings.