Spruce and Fir tree cones
Spruce tree cones hang down and Fir tree cones stand upright. They also differ in the way the needles are attached to shoots (woody pegs for Spruce and pads for Firs). Note that Spruce cones are often found intact on the ground but Fir cones break up on the tree to shed their seeds and are rarely found intact on the ground. Fir cones are also often located at the top of the tree and diffucult to see from the ground.
Spruce and Fir tree cones – Here are the cones of 5 Spruce species – Norway, Sitka, Colorado, Oriental and Serbian and 6 Fir species – European Silver, Caucasian, Grand, Noble Spanish and Korean. Click on any photo to enlarge it.
Conifers develop their seeds within woody cones. Broadleaf trees develop their seeds within ovaries that are part of flowers. The female cones of Pines, Spruces, Firs, Cedars and Larches have a series of overlapping woody scales arranged spirally along the central stem. At each point along the stem a bract scale sits on top of a seed scale and between them lies the seed. The bract scale’s only purpose is to protect the seed, when it is first formed. In Conifers the seed is not protected by an ovary. As the name implies, the bract scale has developed from a modified leaf called a bract. The bract scales in most Conifers are very small and can’t be seen. The seed scales, in comparison, form the outer cone covering and are often called cone scales. However, in some Firs the bract scales stick out from the seed scales and can be used to ID the tree as in the Caucasian Fir in which the yellow tip of each bract scale extends beyond the cone in a distinctive way.
After pollination, the cone closes up, to protect the ovule, and starts to grow. Unlike Broadleaf trees, fertilisation does not always take place immediately after pollination. In some conifers it only takes place after 15 months. During this time the ovule is developing and the pollen tube is growing towards it. Once they meet, fertilisation – involving the combination of the two sets of chromosomes – can take place and the seed can grow. It is protected by the cone until eventually the cone opens, or breaks up, and the seeds are released. The seed cones are woody so that they can protect the ‘naked seed’ of the conifer. The seed is referred to as ‘naked’ because it does not sit within an ovary – as found on Broadleaf trees. Conifers belong to a group of plants called gymnosperms. This word comes from the Greek word for ‘naked seeds’. The woody cone scales are packed closely together and the seed is protected between them.